1	// SPDX-License-Identifier: GPL-2.0-only
2	/*
3	* linux/mm/filemap.c
4	*
5	* Copyright (C) 1994-1999 Linus Torvalds
6	*/
7
8	/*
9	* This file handles the generic file mmap semantics used by
10	* most "normal" filesystems (but you don't /have/ to use this:
11	* the NFS filesystem used to do this differently, for example)
12	*/
13	#include <linux/export.h>
14	#include <linux/compiler.h>
15	#include <linux/dax.h>
16	#include <linux/fs.h>
17	#include <linux/sched/signal.h>
18	#include <linux/uaccess.h>
19	#include <linux/capability.h>
20	#include <linux/kernel_stat.h>
21	#include <linux/gfp.h>
22	#include <linux/mm.h>
23	#include <linux/swap.h>
24	#include <linux/swapops.h>
25	#include <linux/syscalls.h>
26	#include <linux/mman.h>
27	#include <linux/pagemap.h>
28	#include <linux/file.h>
29	#include <linux/uio.h>
30	#include <linux/error-injection.h>
31	#include <linux/hash.h>
32	#include <linux/writeback.h>
33	#include <linux/backing-dev.h>
34	#include <linux/pagevec.h>
35	#include <linux/security.h>
36	#include <linux/cpuset.h>
37	#include <linux/hugetlb.h>
38	#include <linux/memcontrol.h>
39	#include <linux/shmem_fs.h>
40	#include <linux/rmap.h>
41	#include <linux/delayacct.h>
42	#include <linux/psi.h>
43	#include <linux/ramfs.h>
44	#include <linux/page_idle.h>
45	#include <linux/migrate.h>
46	#include <linux/pipe_fs_i.h>
47	#include <linux/splice.h>
48	#include <asm/pgalloc.h>
49	#include <asm/tlbflush.h>
50	#include "internal.h"
51
52	#define CREATE_TRACE_POINTS
53	#include <trace/events/filemap.h>
54
55	/*
56	* FIXME: remove all knowledge of the buffer layer from the core VM
57	*/
58	#include <linux/buffer_head.h> /* for try_to_free_buffers */
59
60	#include <asm/mman.h>
61
62	#include "swap.h"
63
64	/*
65	* Shared mappings implemented 30.11.1994. It's not fully working yet,
66	* though.
67	*
68	* Shared mappings now work. 15.8.1995 Bruno.
69	*
70	* finished 'unifying' the page and buffer cache and SMP-threaded the
71	* page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
72	*
73	* SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
74	*/
75
76	/*
77	* Lock ordering:
78	*
79	* ->i_mmap_rwsem (truncate_pagecache)
80	* ->private_lock (__free_pte->block_dirty_folio)
81	* ->swap_lock (exclusive_swap_page, others)
82	* ->i_pages lock
83	*
84	* ->i_rwsem
85	* ->invalidate_lock (acquired by fs in truncate path)
86	* ->i_mmap_rwsem (truncate->unmap_mapping_range)
87	*
88	* ->mmap_lock
89	* ->i_mmap_rwsem
90	* ->page_table_lock or pte_lock (various, mainly in memory.c)
91	* ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
92	*
93	* ->mmap_lock
94	* ->invalidate_lock (filemap_fault)
95	* ->lock_page (filemap_fault, access_process_vm)
96	*
97	* ->i_rwsem (generic_perform_write)
98	* ->mmap_lock (fault_in_readable->do_page_fault)
99	*
100	* bdi->wb.list_lock
101	* sb_lock (fs/fs-writeback.c)
102	* ->i_pages lock (__sync_single_inode)
103	*
104	* ->i_mmap_rwsem
105	* ->anon_vma.lock (vma_merge)
106	*
107	* ->anon_vma.lock
108	* ->page_table_lock or pte_lock (anon_vma_prepare and various)
109	*
110	* ->page_table_lock or pte_lock
111	* ->swap_lock (try_to_unmap_one)
112	* ->private_lock (try_to_unmap_one)
113	* ->i_pages lock (try_to_unmap_one)
114	* ->lruvec->lru_lock (follow_page->mark_page_accessed)
115	* ->lruvec->lru_lock (check_pte_range->isolate_lru_page)
116	* ->private_lock (page_remove_rmap->set_page_dirty)
117	* ->i_pages lock (page_remove_rmap->set_page_dirty)
118	* bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
119	* ->inode->i_lock (page_remove_rmap->set_page_dirty)
120	* ->memcg->move_lock (page_remove_rmap->folio_memcg_lock)
121	* bdi.wb->list_lock (zap_pte_range->set_page_dirty)
122	* ->inode->i_lock (zap_pte_range->set_page_dirty)
123	* ->private_lock (zap_pte_range->block_dirty_folio)
124	*/
125
126	static void page_cache_delete(struct address_space *mapping,
127	struct folio *folio, void *shadow)
128	{
129	XA_STATE(xas, &mapping->i_pages, folio->index);
130	long nr = 1;
131
132	mapping_set_update(&xas, mapping);
133
134	xas_set_order(xas: &xas, index: folio->index, order: folio_order(folio));
135	nr = folio_nr_pages(folio);
136
137	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
138
139	xas_store(&xas, entry: shadow);
140	xas_init_marks(&xas);
141
142	folio->mapping = NULL;
143	/* Leave page->index set: truncation lookup relies upon it */
144	mapping->nrpages -= nr;
145	}
146
147	static void filemap_unaccount_folio(struct address_space *mapping,
148	struct folio *folio)
149	{
150	long nr;
151
152	VM_BUG_ON_FOLIO(folio_mapped(folio), folio);
153	if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) {
154	pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
155	current->comm, folio_pfn(folio));
156	dump_page(page: &folio->page, reason: "still mapped when deleted");
157	dump_stack();
158	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
159
160	if (mapping_exiting(mapping) && !folio_test_large(folio)) {
161	int mapcount = page_mapcount(page: &folio->page);
162
163	if (folio_ref_count(folio) >= mapcount + 2) {
164	/*
165	* All vmas have already been torn down, so it's
166	* a good bet that actually the page is unmapped
167	* and we'd rather not leak it: if we're wrong,
168	* another bad page check should catch it later.
169	*/
170	page_mapcount_reset(page: &folio->page);
171	folio_ref_sub(folio, nr: mapcount);
172	}
173	}
174	}
175
176	/* hugetlb folios do not participate in page cache accounting. */
177	if (folio_test_hugetlb(folio))
178	return;
179
180	nr = folio_nr_pages(folio);
181
182	__lruvec_stat_mod_folio(folio, idx: NR_FILE_PAGES, val: -nr);
183	if (folio_test_swapbacked(folio)) {
184	__lruvec_stat_mod_folio(folio, idx: NR_SHMEM, val: -nr);
185	if (folio_test_pmd_mappable(folio))
186	__lruvec_stat_mod_folio(folio, idx: NR_SHMEM_THPS, val: -nr);
187	} else if (folio_test_pmd_mappable(folio)) {
188	__lruvec_stat_mod_folio(folio, idx: NR_FILE_THPS, val: -nr);
189	filemap_nr_thps_dec(mapping);
190	}
191
192	/*
193	* At this point folio must be either written or cleaned by
194	* truncate. Dirty folio here signals a bug and loss of
195	* unwritten data - on ordinary filesystems.
196	*
197	* But it's harmless on in-memory filesystems like tmpfs; and can
198	* occur when a driver which did get_user_pages() sets page dirty
199	* before putting it, while the inode is being finally evicted.
200	*
201	* Below fixes dirty accounting after removing the folio entirely
202	* but leaves the dirty flag set: it has no effect for truncated
203	* folio and anyway will be cleared before returning folio to
204	* buddy allocator.
205	*/
206	if (WARN_ON_ONCE(folio_test_dirty(folio) &&
207	mapping_can_writeback(mapping)))
208	folio_account_cleaned(folio, wb: inode_to_wb(inode: mapping->host));
209	}
210
211	/*
212	* Delete a page from the page cache and free it. Caller has to make
213	* sure the page is locked and that nobody else uses it - or that usage
214	* is safe. The caller must hold the i_pages lock.
215	*/
216	void __filemap_remove_folio(struct folio *folio, void *shadow)
217	{
218	struct address_space *mapping = folio->mapping;
219
220	trace_mm_filemap_delete_from_page_cache(folio);
221	filemap_unaccount_folio(mapping, folio);
222	page_cache_delete(mapping, folio, shadow);
223	}
224
225	void filemap_free_folio(struct address_space *mapping, struct folio *folio)
226	{
227	void (*free_folio)(struct folio *);
228	int refs = 1;
229
230	free_folio = mapping->a_ops->free_folio;
231	if (free_folio)
232	free_folio(folio);
233
234	if (folio_test_large(folio))
235	refs = folio_nr_pages(folio);
236	folio_put_refs(folio, refs);
237	}
238
239	/**
240	* filemap_remove_folio - Remove folio from page cache.
241	* @folio: The folio.
242	*
243	* This must be called only on folios that are locked and have been
244	* verified to be in the page cache. It will never put the folio into
245	* the free list because the caller has a reference on the page.
246	*/
247	void filemap_remove_folio(struct folio *folio)
248	{
249	struct address_space *mapping = folio->mapping;
250
251	BUG_ON(!folio_test_locked(folio));
252	spin_lock(lock: &mapping->host->i_lock);
253	xa_lock_irq(&mapping->i_pages);
254	__filemap_remove_folio(folio, NULL);
255	xa_unlock_irq(&mapping->i_pages);
256	if (mapping_shrinkable(mapping))
257	inode_add_lru(inode: mapping->host);
258	spin_unlock(lock: &mapping->host->i_lock);
259
260	filemap_free_folio(mapping, folio);
261	}
262
263	/*
264	* page_cache_delete_batch - delete several folios from page cache
265	* @mapping: the mapping to which folios belong
266	* @fbatch: batch of folios to delete
267	*
268	* The function walks over mapping->i_pages and removes folios passed in
269	* @fbatch from the mapping. The function expects @fbatch to be sorted
270	* by page index and is optimised for it to be dense.
271	* It tolerates holes in @fbatch (mapping entries at those indices are not
272	* modified).
273	*
274	* The function expects the i_pages lock to be held.
275	*/
276	static void page_cache_delete_batch(struct address_space *mapping,
277	struct folio_batch *fbatch)
278	{
279	XA_STATE(xas, &mapping->i_pages, fbatch->folios[0]->index);
280	long total_pages = 0;
281	int i = 0;
282	struct folio *folio;
283
284	mapping_set_update(&xas, mapping);
285	xas_for_each(&xas, folio, ULONG_MAX) {
286	if (i >= folio_batch_count(fbatch))
287	break;
288
289	/* A swap/dax/shadow entry got inserted? Skip it. */
290	if (xa_is_value(entry: folio))
291	continue;
292	/*
293	* A page got inserted in our range? Skip it. We have our
294	* pages locked so they are protected from being removed.
295	* If we see a page whose index is higher than ours, it
296	* means our page has been removed, which shouldn't be
297	* possible because we're holding the PageLock.
298	*/
299	if (folio != fbatch->folios[i]) {
300	VM_BUG_ON_FOLIO(folio->index >
301	fbatch->folios[i]->index, folio);
302	continue;
303	}
304
305	WARN_ON_ONCE(!folio_test_locked(folio));
306
307	folio->mapping = NULL;
308	/* Leave folio->index set: truncation lookup relies on it */
309
310	i++;
311	xas_store(&xas, NULL);
312	total_pages += folio_nr_pages(folio);
313	}
314	mapping->nrpages -= total_pages;
315	}
316
317	void delete_from_page_cache_batch(struct address_space *mapping,
318	struct folio_batch *fbatch)
319	{
320	int i;
321
322	if (!folio_batch_count(fbatch))
323	return;
324
325	spin_lock(lock: &mapping->host->i_lock);
326	xa_lock_irq(&mapping->i_pages);
327	for (i = 0; i < folio_batch_count(fbatch); i++) {
328	struct folio *folio = fbatch->folios[i];
329
330	trace_mm_filemap_delete_from_page_cache(folio);
331	filemap_unaccount_folio(mapping, folio);
332	}
333	page_cache_delete_batch(mapping, fbatch);
334	xa_unlock_irq(&mapping->i_pages);
335	if (mapping_shrinkable(mapping))
336	inode_add_lru(inode: mapping->host);
337	spin_unlock(lock: &mapping->host->i_lock);
338
339	for (i = 0; i < folio_batch_count(fbatch); i++)
340	filemap_free_folio(mapping, folio: fbatch->folios[i]);
341	}
342
343	int filemap_check_errors(struct address_space *mapping)
344	{
345	int ret = 0;
346	/* Check for outstanding write errors */
347	if (test_bit(AS_ENOSPC, &mapping->flags) &&
348	test_and_clear_bit(nr: AS_ENOSPC, addr: &mapping->flags))
349	ret = -ENOSPC;
350	if (test_bit(AS_EIO, &mapping->flags) &&
351	test_and_clear_bit(nr: AS_EIO, addr: &mapping->flags))
352	ret = -EIO;
353	return ret;
354	}
355	EXPORT_SYMBOL(filemap_check_errors);
356
357	static int filemap_check_and_keep_errors(struct address_space *mapping)
358	{
359	/* Check for outstanding write errors */
360	if (test_bit(AS_EIO, &mapping->flags))
361	return -EIO;
362	if (test_bit(AS_ENOSPC, &mapping->flags))
363	return -ENOSPC;
364	return 0;
365	}
366
367	/**
368	* filemap_fdatawrite_wbc - start writeback on mapping dirty pages in range
369	* @mapping: address space structure to write
370	* @wbc: the writeback_control controlling the writeout
371	*
372	* Call writepages on the mapping using the provided wbc to control the
373	* writeout.
374	*
375	* Return: %0 on success, negative error code otherwise.
376	*/
377	int filemap_fdatawrite_wbc(struct address_space *mapping,
378	struct writeback_control *wbc)
379	{
380	int ret;
381
382	if (!mapping_can_writeback(mapping) ||
383	!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
384	return 0;
385
386	wbc_attach_fdatawrite_inode(wbc, inode: mapping->host);
387	ret = do_writepages(mapping, wbc);
388	wbc_detach_inode(wbc);
389	return ret;
390	}
391	EXPORT_SYMBOL(filemap_fdatawrite_wbc);
392
393	/**
394	* __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
395	* @mapping: address space structure to write
396	* @start: offset in bytes where the range starts
397	* @end: offset in bytes where the range ends (inclusive)
398	* @sync_mode: enable synchronous operation
399	*
400	* Start writeback against all of a mapping's dirty pages that lie
401	* within the byte offsets <start, end> inclusive.
402	*
403	* If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
404	* opposed to a regular memory cleansing writeback. The difference between
405	* these two operations is that if a dirty page/buffer is encountered, it must
406	* be waited upon, and not just skipped over.
407	*
408	* Return: %0 on success, negative error code otherwise.
409	*/
410	int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
411	loff_t end, int sync_mode)
412	{
413	struct writeback_control wbc = {
414	.sync_mode = sync_mode,
415	.nr_to_write = LONG_MAX,
416	.range_start = start,
417	.range_end = end,
418	};
419
420	return filemap_fdatawrite_wbc(mapping, &wbc);
421	}
422
423	static inline int __filemap_fdatawrite(struct address_space *mapping,
424	int sync_mode)
425	{
426	return __filemap_fdatawrite_range(mapping, start: 0, LLONG_MAX, sync_mode);
427	}
428
429	int filemap_fdatawrite(struct address_space *mapping)
430	{
431	return __filemap_fdatawrite(mapping, sync_mode: WB_SYNC_ALL);
432	}
433	EXPORT_SYMBOL(filemap_fdatawrite);
434
435	int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
436	loff_t end)
437	{
438	return __filemap_fdatawrite_range(mapping, start, end, sync_mode: WB_SYNC_ALL);
439	}
440	EXPORT_SYMBOL(filemap_fdatawrite_range);
441
442	/**
443	* filemap_flush - mostly a non-blocking flush
444	* @mapping: target address_space
445	*
446	* This is a mostly non-blocking flush. Not suitable for data-integrity
447	* purposes - I/O may not be started against all dirty pages.
448	*
449	* Return: %0 on success, negative error code otherwise.
450	*/
451	int filemap_flush(struct address_space *mapping)
452	{
453	return __filemap_fdatawrite(mapping, sync_mode: WB_SYNC_NONE);
454	}
455	EXPORT_SYMBOL(filemap_flush);
456
457	/**
458	* filemap_range_has_page - check if a page exists in range.
459	* @mapping: address space within which to check
460	* @start_byte: offset in bytes where the range starts
461	* @end_byte: offset in bytes where the range ends (inclusive)
462	*
463	* Find at least one page in the range supplied, usually used to check if
464	* direct writing in this range will trigger a writeback.
465	*
466	* Return: %true if at least one page exists in the specified range,
467	* %false otherwise.
468	*/
469	bool filemap_range_has_page(struct address_space *mapping,
470	loff_t start_byte, loff_t end_byte)
471	{
472	struct folio *folio;
473	XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
474	pgoff_t max = end_byte >> PAGE_SHIFT;
475
476	if (end_byte < start_byte)
477	return false;
478
479	rcu_read_lock();
480	for (;;) {
481	folio = xas_find(&xas, max);
482	if (xas_retry(xas: &xas, entry: folio))
483	continue;
484	/* Shadow entries don't count */
485	if (xa_is_value(entry: folio))
486	continue;
487	/*
488	* We don't need to try to pin this page; we're about to
489	* release the RCU lock anyway. It is enough to know that
490	* there was a page here recently.
491	*/
492	break;
493	}
494	rcu_read_unlock();
495
496	return folio != NULL;
497	}
498	EXPORT_SYMBOL(filemap_range_has_page);
499
500	static void __filemap_fdatawait_range(struct address_space *mapping,
501	loff_t start_byte, loff_t end_byte)
502	{
503	pgoff_t index = start_byte >> PAGE_SHIFT;
504	pgoff_t end = end_byte >> PAGE_SHIFT;
505	struct folio_batch fbatch;
506	unsigned nr_folios;
507
508	folio_batch_init(fbatch: &fbatch);
509
510	while (index <= end) {
511	unsigned i;
512
513	nr_folios = filemap_get_folios_tag(mapping, start: &index, end,
514	PAGECACHE_TAG_WRITEBACK, fbatch: &fbatch);
515
516	if (!nr_folios)
517	break;
518
519	for (i = 0; i < nr_folios; i++) {
520	struct folio *folio = fbatch.folios[i];
521
522	folio_wait_writeback(folio);
523	folio_clear_error(folio);
524	}
525	folio_batch_release(fbatch: &fbatch);
526	cond_resched();
527	}
528	}
529
530	/**
531	* filemap_fdatawait_range - wait for writeback to complete
532	* @mapping: address space structure to wait for
533	* @start_byte: offset in bytes where the range starts
534	* @end_byte: offset in bytes where the range ends (inclusive)
535	*
536	* Walk the list of under-writeback pages of the given address space
537	* in the given range and wait for all of them. Check error status of
538	* the address space and return it.
539	*
540	* Since the error status of the address space is cleared by this function,
541	* callers are responsible for checking the return value and handling and/or
542	* reporting the error.
543	*
544	* Return: error status of the address space.
545	*/
546	int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
547	loff_t end_byte)
548	{
549	__filemap_fdatawait_range(mapping, start_byte, end_byte);
550	return filemap_check_errors(mapping);
551	}
552	EXPORT_SYMBOL(filemap_fdatawait_range);
553
554	/**
555	* filemap_fdatawait_range_keep_errors - wait for writeback to complete
556	* @mapping: address space structure to wait for
557	* @start_byte: offset in bytes where the range starts
558	* @end_byte: offset in bytes where the range ends (inclusive)
559	*
560	* Walk the list of under-writeback pages of the given address space in the
561	* given range and wait for all of them. Unlike filemap_fdatawait_range(),
562	* this function does not clear error status of the address space.
563	*
564	* Use this function if callers don't handle errors themselves. Expected
565	* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
566	* fsfreeze(8)
567	*/
568	int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
569	loff_t start_byte, loff_t end_byte)
570	{
571	__filemap_fdatawait_range(mapping, start_byte, end_byte);
572	return filemap_check_and_keep_errors(mapping);
573	}
574	EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
575
576	/**
577	* file_fdatawait_range - wait for writeback to complete
578	* @file: file pointing to address space structure to wait for
579	* @start_byte: offset in bytes where the range starts
580	* @end_byte: offset in bytes where the range ends (inclusive)
581	*
582	* Walk the list of under-writeback pages of the address space that file
583	* refers to, in the given range and wait for all of them. Check error
584	* status of the address space vs. the file->f_wb_err cursor and return it.
585	*
586	* Since the error status of the file is advanced by this function,
587	* callers are responsible for checking the return value and handling and/or
588	* reporting the error.
589	*
590	* Return: error status of the address space vs. the file->f_wb_err cursor.
591	*/
592	int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
593	{
594	struct address_space *mapping = file->f_mapping;
595
596	__filemap_fdatawait_range(mapping, start_byte, end_byte);
597	return file_check_and_advance_wb_err(file);
598	}
599	EXPORT_SYMBOL(file_fdatawait_range);
600
601	/**
602	* filemap_fdatawait_keep_errors - wait for writeback without clearing errors
603	* @mapping: address space structure to wait for
604	*
605	* Walk the list of under-writeback pages of the given address space
606	* and wait for all of them. Unlike filemap_fdatawait(), this function
607	* does not clear error status of the address space.
608	*
609	* Use this function if callers don't handle errors themselves. Expected
610	* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
611	* fsfreeze(8)
612	*
613	* Return: error status of the address space.
614	*/
615	int filemap_fdatawait_keep_errors(struct address_space *mapping)
616	{
617	__filemap_fdatawait_range(mapping, start_byte: 0, LLONG_MAX);
618	return filemap_check_and_keep_errors(mapping);
619	}
620	EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
621
622	/* Returns true if writeback might be needed or already in progress. */
623	static bool mapping_needs_writeback(struct address_space *mapping)
624	{
625	return mapping->nrpages;
626	}
627
628	bool filemap_range_has_writeback(struct address_space *mapping,
629	loff_t start_byte, loff_t end_byte)
630	{
631	XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
632	pgoff_t max = end_byte >> PAGE_SHIFT;
633	struct folio *folio;
634
635	if (end_byte < start_byte)
636	return false;
637
638	rcu_read_lock();
639	xas_for_each(&xas, folio, max) {
640	if (xas_retry(xas: &xas, entry: folio))
641	continue;
642	if (xa_is_value(entry: folio))
643	continue;
644	if (folio_test_dirty(folio) || folio_test_locked(folio) ||
645	folio_test_writeback(folio))
646	break;
647	}
648	rcu_read_unlock();
649	return folio != NULL;
650	}
651	EXPORT_SYMBOL_GPL(filemap_range_has_writeback);
652
653	/**
654	* filemap_write_and_wait_range - write out & wait on a file range
655	* @mapping: the address_space for the pages
656	* @lstart: offset in bytes where the range starts
657	* @lend: offset in bytes where the range ends (inclusive)
658	*
659	* Write out and wait upon file offsets lstart->lend, inclusive.
660	*
661	* Note that @lend is inclusive (describes the last byte to be written) so
662	* that this function can be used to write to the very end-of-file (end = -1).
663	*
664	* Return: error status of the address space.
665	*/
666	int filemap_write_and_wait_range(struct address_space *mapping,
667	loff_t lstart, loff_t lend)
668	{
669	int err = 0, err2;
670
671	if (lend < lstart)
672	return 0;
673
674	if (mapping_needs_writeback(mapping)) {
675	err = __filemap_fdatawrite_range(mapping, start: lstart, end: lend,
676	sync_mode: WB_SYNC_ALL);
677	/*
678	* Even if the above returned error, the pages may be
679	* written partially (e.g. -ENOSPC), so we wait for it.
680	* But the -EIO is special case, it may indicate the worst
681	* thing (e.g. bug) happened, so we avoid waiting for it.
682	*/
683	if (err != -EIO)
684	__filemap_fdatawait_range(mapping, start_byte: lstart, end_byte: lend);
685	}
686	err2 = filemap_check_errors(mapping);
687	if (!err)
688	err = err2;
689	return err;
690	}
691	EXPORT_SYMBOL(filemap_write_and_wait_range);
692
693	void __filemap_set_wb_err(struct address_space *mapping, int err)
694	{
695	errseq_t eseq = errseq_set(eseq: &mapping->wb_err, err);
696
697	trace_filemap_set_wb_err(mapping, eseq);
698	}
699	EXPORT_SYMBOL(__filemap_set_wb_err);
700
701	/**
702	* file_check_and_advance_wb_err - report wb error (if any) that was previously
703	* and advance wb_err to current one
704	* @file: struct file on which the error is being reported
705	*
706	* When userland calls fsync (or something like nfsd does the equivalent), we
707	* want to report any writeback errors that occurred since the last fsync (or
708	* since the file was opened if there haven't been any).
709	*
710	* Grab the wb_err from the mapping. If it matches what we have in the file,
711	* then just quickly return 0. The file is all caught up.
712	*
713	* If it doesn't match, then take the mapping value, set the "seen" flag in
714	* it and try to swap it into place. If it works, or another task beat us
715	* to it with the new value, then update the f_wb_err and return the error
716	* portion. The error at this point must be reported via proper channels
717	* (a'la fsync, or NFS COMMIT operation, etc.).
718	*
719	* While we handle mapping->wb_err with atomic operations, the f_wb_err
720	* value is protected by the f_lock since we must ensure that it reflects
721	* the latest value swapped in for this file descriptor.
722	*
723	* Return: %0 on success, negative error code otherwise.
724	*/
725	int file_check_and_advance_wb_err(struct file *file)
726	{
727	int err = 0;
728	errseq_t old = READ_ONCE(file->f_wb_err);
729	struct address_space *mapping = file->f_mapping;
730
731	/* Locklessly handle the common case where nothing has changed */
732	if (errseq_check(eseq: &mapping->wb_err, since: old)) {
733	/* Something changed, must use slow path */
734	spin_lock(lock: &file->f_lock);
735	old = file->f_wb_err;
736	err = errseq_check_and_advance(eseq: &mapping->wb_err,
737	since: &file->f_wb_err);
738	trace_file_check_and_advance_wb_err(file, old);
739	spin_unlock(lock: &file->f_lock);
740	}
741
742	/*
743	* We're mostly using this function as a drop in replacement for
744	* filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
745	* that the legacy code would have had on these flags.
746	*/
747	clear_bit(nr: AS_EIO, addr: &mapping->flags);
748	clear_bit(nr: AS_ENOSPC, addr: &mapping->flags);
749	return err;
750	}
751	EXPORT_SYMBOL(file_check_and_advance_wb_err);
752
753	/**
754	* file_write_and_wait_range - write out & wait on a file range
755	* @file: file pointing to address_space with pages
756	* @lstart: offset in bytes where the range starts
757	* @lend: offset in bytes where the range ends (inclusive)
758	*
759	* Write out and wait upon file offsets lstart->lend, inclusive.
760	*
761	* Note that @lend is inclusive (describes the last byte to be written) so
762	* that this function can be used to write to the very end-of-file (end = -1).
763	*
764	* After writing out and waiting on the data, we check and advance the
765	* f_wb_err cursor to the latest value, and return any errors detected there.
766	*
767	* Return: %0 on success, negative error code otherwise.
768	*/
769	int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
770	{
771	int err = 0, err2;
772	struct address_space *mapping = file->f_mapping;
773
774	if (lend < lstart)
775	return 0;
776
777	if (mapping_needs_writeback(mapping)) {
778	err = __filemap_fdatawrite_range(mapping, start: lstart, end: lend,
779	sync_mode: WB_SYNC_ALL);
780	/* See comment of filemap_write_and_wait() */
781	if (err != -EIO)
782	__filemap_fdatawait_range(mapping, start_byte: lstart, end_byte: lend);
783	}
784	err2 = file_check_and_advance_wb_err(file);
785	if (!err)
786	err = err2;
787	return err;
788	}
789	EXPORT_SYMBOL(file_write_and_wait_range);
790
791	/**
792	* replace_page_cache_folio - replace a pagecache folio with a new one
793	* @old: folio to be replaced
794	* @new: folio to replace with
795	*
796	* This function replaces a folio in the pagecache with a new one. On
797	* success it acquires the pagecache reference for the new folio and
798	* drops it for the old folio. Both the old and new folios must be
799	* locked. This function does not add the new folio to the LRU, the
800	* caller must do that.
801	*
802	* The remove + add is atomic. This function cannot fail.
803	*/
804	void replace_page_cache_folio(struct folio *old, struct folio *new)
805	{
806	struct address_space *mapping = old->mapping;
807	void (*free_folio)(struct folio *) = mapping->a_ops->free_folio;
808	pgoff_t offset = old->index;
809	XA_STATE(xas, &mapping->i_pages, offset);
810
811	VM_BUG_ON_FOLIO(!folio_test_locked(old), old);
812	VM_BUG_ON_FOLIO(!folio_test_locked(new), new);
813	VM_BUG_ON_FOLIO(new->mapping, new);
814
815	folio_get(folio: new);
816	new->mapping = mapping;
817	new->index = offset;
818
819	mem_cgroup_replace_folio(old, new);
820
821	xas_lock_irq(&xas);
822	xas_store(&xas, entry: new);
823
824	old->mapping = NULL;
825	/* hugetlb pages do not participate in page cache accounting. */
826	if (!folio_test_hugetlb(folio: old))
827	__lruvec_stat_sub_folio(folio: old, idx: NR_FILE_PAGES);
828	if (!folio_test_hugetlb(folio: new))
829	__lruvec_stat_add_folio(folio: new, idx: NR_FILE_PAGES);
830	if (folio_test_swapbacked(folio: old))
831	__lruvec_stat_sub_folio(folio: old, idx: NR_SHMEM);
832	if (folio_test_swapbacked(folio: new))
833	__lruvec_stat_add_folio(folio: new, idx: NR_SHMEM);
834	xas_unlock_irq(&xas);
835	if (free_folio)
836	free_folio(old);
837	folio_put(folio: old);
838	}
839	EXPORT_SYMBOL_GPL(replace_page_cache_folio);
840
841	noinline int __filemap_add_folio(struct address_space *mapping,
842	struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp)
843	{
844	XA_STATE(xas, &mapping->i_pages, index);
845	int huge = folio_test_hugetlb(folio);
846	bool charged = false;
847	long nr = 1;
848
849	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
850	VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
851	mapping_set_update(&xas, mapping);
852
853	if (!huge) {
854	int error = mem_cgroup_charge(folio, NULL, gfp);
855	if (error)
856	return error;
857	charged = true;
858	}
859
860	VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
861	xas_set_order(xas: &xas, index, order: folio_order(folio));
862	nr = folio_nr_pages(folio);
863
864	gfp &= GFP_RECLAIM_MASK;
865	folio_ref_add(folio, nr);
866	folio->mapping = mapping;
867	folio->index = xas.xa_index;
868
869	do {
870	unsigned int order = xa_get_order(xas.xa, index: xas.xa_index);
871	void *entry, *old = NULL;
872
873	if (order > folio_order(folio))
874	xas_split_alloc(&xas, entry: xa_load(xas.xa, index: xas.xa_index),
875	order, gfp);
876	xas_lock_irq(&xas);
877	xas_for_each_conflict(&xas, entry) {
878	old = entry;
879	if (!xa_is_value(entry)) {
880	xas_set_err(xas: &xas, err: -EEXIST);
881	goto unlock;
882	}
883	}
884
885	if (old) {
886	if (shadowp)
887	*shadowp = old;
888	/* entry may have been split before we acquired lock */
889	order = xa_get_order(xas.xa, index: xas.xa_index);
890	if (order > folio_order(folio)) {
891	/* How to handle large swap entries? */
892	BUG_ON(shmem_mapping(mapping));
893	xas_split(&xas, entry: old, order);
894	xas_reset(xas: &xas);
895	}
896	}
897
898	xas_store(&xas, entry: folio);
899	if (xas_error(xas: &xas))
900	goto unlock;
901
902	mapping->nrpages += nr;
903
904	/* hugetlb pages do not participate in page cache accounting */
905	if (!huge) {
906	__lruvec_stat_mod_folio(folio, idx: NR_FILE_PAGES, val: nr);
907	if (folio_test_pmd_mappable(folio))
908	__lruvec_stat_mod_folio(folio,
909	idx: NR_FILE_THPS, val: nr);
910	}
911	unlock:
912	xas_unlock_irq(&xas);
913	} while (xas_nomem(&xas, gfp));
914
915	if (xas_error(xas: &xas))
916	goto error;
917
918	trace_mm_filemap_add_to_page_cache(folio);
919	return 0;
920	error:
921	if (charged)
922	mem_cgroup_uncharge(folio);
923	folio->mapping = NULL;
924	/* Leave page->index set: truncation relies upon it */
925	folio_put_refs(folio, refs: nr);
926	return xas_error(xas: &xas);
927	}
928	ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO);
929
930	int filemap_add_folio(struct address_space *mapping, struct folio *folio,
931	pgoff_t index, gfp_t gfp)
932	{
933	void *shadow = NULL;
934	int ret;
935
936	__folio_set_locked(folio);
937	ret = __filemap_add_folio(mapping, folio, index, gfp, shadowp: &shadow);
938	if (unlikely(ret))
939	__folio_clear_locked(folio);
940	else {
941	/*
942	* The folio might have been evicted from cache only
943	* recently, in which case it should be activated like
944	* any other repeatedly accessed folio.
945	* The exception is folios getting rewritten; evicting other
946	* data from the working set, only to cache data that will
947	* get overwritten with something else, is a waste of memory.
948	*/
949	WARN_ON_ONCE(folio_test_active(folio));
950	if (!(gfp & __GFP_WRITE) && shadow)
951	workingset_refault(folio, shadow);
952	folio_add_lru(folio);
953	}
954	return ret;
955	}
956	EXPORT_SYMBOL_GPL(filemap_add_folio);
957
958	#ifdef CONFIG_NUMA
959	struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order)
960	{
961	int n;
962	struct folio *folio;
963
964	if (cpuset_do_page_mem_spread()) {
965	unsigned int cpuset_mems_cookie;
966	do {
967	cpuset_mems_cookie = read_mems_allowed_begin();
968	n = cpuset_mem_spread_node();
969	folio = __folio_alloc_node(gfp, order, nid: n);
970	} while (!folio && read_mems_allowed_retry(seq: cpuset_mems_cookie));
971
972	return folio;
973	}
974	return folio_alloc(gfp, order);
975	}
976	EXPORT_SYMBOL(filemap_alloc_folio);
977	#endif
978
979	/*
980	* filemap_invalidate_lock_two - lock invalidate_lock for two mappings
981	*
982	* Lock exclusively invalidate_lock of any passed mapping that is not NULL.
983	*
984	* @mapping1: the first mapping to lock
985	* @mapping2: the second mapping to lock
986	*/
987	void filemap_invalidate_lock_two(struct address_space *mapping1,
988	struct address_space *mapping2)
989	{
990	if (mapping1 > mapping2)
991	swap(mapping1, mapping2);
992	if (mapping1)
993	down_write(sem: &mapping1->invalidate_lock);
994	if (mapping2 && mapping1 != mapping2)
995	down_write_nested(sem: &mapping2->invalidate_lock, subclass: 1);
996	}
997	EXPORT_SYMBOL(filemap_invalidate_lock_two);
998
999	/*
1000	* filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings
1001	*
1002	* Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
1003	*
1004	* @mapping1: the first mapping to unlock
1005	* @mapping2: the second mapping to unlock
1006	*/
1007	void filemap_invalidate_unlock_two(struct address_space *mapping1,
1008	struct address_space *mapping2)
1009	{
1010	if (mapping1)
1011	up_write(sem: &mapping1->invalidate_lock);
1012	if (mapping2 && mapping1 != mapping2)
1013	up_write(sem: &mapping2->invalidate_lock);
1014	}
1015	EXPORT_SYMBOL(filemap_invalidate_unlock_two);
1016
1017	/*
1018	* In order to wait for pages to become available there must be
1019	* waitqueues associated with pages. By using a hash table of
1020	* waitqueues where the bucket discipline is to maintain all
1021	* waiters on the same queue and wake all when any of the pages
1022	* become available, and for the woken contexts to check to be
1023	* sure the appropriate page became available, this saves space
1024	* at a cost of "thundering herd" phenomena during rare hash
1025	* collisions.
1026	*/
1027	#define PAGE_WAIT_TABLE_BITS 8
1028	#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
1029	static wait_queue_head_t folio_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
1030
1031	static wait_queue_head_t *folio_waitqueue(struct folio *folio)
1032	{
1033	return &folio_wait_table[hash_ptr(ptr: folio, PAGE_WAIT_TABLE_BITS)];
1034	}
1035
1036	void __init pagecache_init(void)
1037	{
1038	int i;
1039
1040	for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
1041	init_waitqueue_head(&folio_wait_table[i]);
1042
1043	page_writeback_init();
1044	}
1045
1046	/*
1047	* The page wait code treats the "wait->flags" somewhat unusually, because
1048	* we have multiple different kinds of waits, not just the usual "exclusive"
1049	* one.
1050	*
1051	* We have:
1052	*
1053	* (a) no special bits set:
1054	*
1055	* We're just waiting for the bit to be released, and when a waker
1056	* calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up,
1057	* and remove it from the wait queue.
1058	*
1059	* Simple and straightforward.
1060	*
1061	* (b) WQ_FLAG_EXCLUSIVE:
1062	*
1063	* The waiter is waiting to get the lock, and only one waiter should
1064	* be woken up to avoid any thundering herd behavior. We'll set the
1065	* WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue.
1066	*
1067	* This is the traditional exclusive wait.
1068	*
1069	* (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM:
1070	*
1071	* The waiter is waiting to get the bit, and additionally wants the
1072	* lock to be transferred to it for fair lock behavior. If the lock
1073	* cannot be taken, we stop walking the wait queue without waking
1074	* the waiter.
1075	*
1076	* This is the "fair lock handoff" case, and in addition to setting
1077	* WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see
1078	* that it now has the lock.
1079	*/
1080	static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
1081	{
1082	unsigned int flags;
1083	struct wait_page_key *key = arg;
1084	struct wait_page_queue *wait_page
1085	= container_of(wait, struct wait_page_queue, wait);
1086
1087	if (!wake_page_match(wait_page, key))
1088	return 0;
1089
1090	/*
1091	* If it's a lock handoff wait, we get the bit for it, and
1092	* stop walking (and do not wake it up) if we can't.
1093	*/
1094	flags = wait->flags;
1095	if (flags & WQ_FLAG_EXCLUSIVE) {
1096	if (test_bit(key->bit_nr, &key->folio->flags))
1097	return -1;
1098	if (flags & WQ_FLAG_CUSTOM) {
1099	if (test_and_set_bit(nr: key->bit_nr, addr: &key->folio->flags))
1100	return -1;
1101	flags |= WQ_FLAG_DONE;
1102	}
1103	}
1104
1105	/*
1106	* We are holding the wait-queue lock, but the waiter that
1107	* is waiting for this will be checking the flags without
1108	* any locking.
1109	*
1110	* So update the flags atomically, and wake up the waiter
1111	* afterwards to avoid any races. This store-release pairs
1112	* with the load-acquire in folio_wait_bit_common().
1113	*/
1114	smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
1115	wake_up_state(tsk: wait->private, state: mode);
1116
1117	/*
1118	* Ok, we have successfully done what we're waiting for,
1119	* and we can unconditionally remove the wait entry.
1120	*
1121	* Note that this pairs with the "finish_wait()" in the
1122	* waiter, and has to be the absolute last thing we do.
1123	* After this list_del_init(&wait->entry) the wait entry
1124	* might be de-allocated and the process might even have
1125	* exited.
1126	*/
1127	list_del_init_careful(entry: &wait->entry);
1128	return (flags & WQ_FLAG_EXCLUSIVE) != 0;
1129	}
1130
1131	static void folio_wake_bit(struct folio *folio, int bit_nr)
1132	{
1133	wait_queue_head_t *q = folio_waitqueue(folio);
1134	struct wait_page_key key;
1135	unsigned long flags;
1136
1137	key.folio = folio;
1138	key.bit_nr = bit_nr;
1139	key.page_match = 0;
1140
1141	spin_lock_irqsave(&q->lock, flags);
1142	__wake_up_locked_key(wq_head: q, TASK_NORMAL, key: &key);
1143
1144	/*
1145	* It's possible to miss clearing waiters here, when we woke our page
1146	* waiters, but the hashed waitqueue has waiters for other pages on it.
1147	* That's okay, it's a rare case. The next waker will clear it.
1148	*
1149	* Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE,
1150	* other), the flag may be cleared in the course of freeing the page;
1151	* but that is not required for correctness.
1152	*/
1153	if (!waitqueue_active(wq_head: q) || !key.page_match)
1154	folio_clear_waiters(folio);
1155
1156	spin_unlock_irqrestore(lock: &q->lock, flags);
1157	}
1158
1159	/*
1160	* A choice of three behaviors for folio_wait_bit_common():
1161	*/
1162	enum behavior {
1163	EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
1164	* __folio_lock() waiting on then setting PG_locked.
1165	*/
1166	SHARED, /* Hold ref to page and check the bit when woken, like
1167	* folio_wait_writeback() waiting on PG_writeback.
1168	*/
1169	DROP, /* Drop ref to page before wait, no check when woken,
1170	* like folio_put_wait_locked() on PG_locked.
1171	*/
1172	};
1173
1174	/*
1175	* Attempt to check (or get) the folio flag, and mark us done
1176	* if successful.
1177	*/
1178	static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
1179	struct wait_queue_entry *wait)
1180	{
1181	if (wait->flags & WQ_FLAG_EXCLUSIVE) {
1182	if (test_and_set_bit(nr: bit_nr, addr: &folio->flags))
1183	return false;
1184	} else if (test_bit(bit_nr, &folio->flags))
1185	return false;
1186
1187	wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
1188	return true;
1189	}
1190
1191	/* How many times do we accept lock stealing from under a waiter? */
1192	int sysctl_page_lock_unfairness = 5;
1193
1194	static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
1195	int state, enum behavior behavior)
1196	{
1197	wait_queue_head_t *q = folio_waitqueue(folio);
1198	int unfairness = sysctl_page_lock_unfairness;
1199	struct wait_page_queue wait_page;
1200	wait_queue_entry_t *wait = &wait_page.wait;
1201	bool thrashing = false;
1202	unsigned long pflags;
1203	bool in_thrashing;
1204
1205	if (bit_nr == PG_locked &&
1206	!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
1207	delayacct_thrashing_start(in_thrashing: &in_thrashing);
1208	psi_memstall_enter(flags: &pflags);
1209	thrashing = true;
1210	}
1211
1212	init_wait(wait);
1213	wait->func = wake_page_function;
1214	wait_page.folio = folio;
1215	wait_page.bit_nr = bit_nr;
1216
1217	repeat:
1218	wait->flags = 0;
1219	if (behavior == EXCLUSIVE) {
1220	wait->flags = WQ_FLAG_EXCLUSIVE;
1221	if (--unfairness < 0)
1222	wait->flags |= WQ_FLAG_CUSTOM;
1223	}
1224
1225	/*
1226	* Do one last check whether we can get the
1227	* page bit synchronously.
1228	*
1229	* Do the folio_set_waiters() marking before that
1230	* to let any waker we _just_ missed know they
1231	* need to wake us up (otherwise they'll never
1232	* even go to the slow case that looks at the
1233	* page queue), and add ourselves to the wait
1234	* queue if we need to sleep.
1235	*
1236	* This part needs to be done under the queue
1237	* lock to avoid races.
1238	*/
1239	spin_lock_irq(lock: &q->lock);
1240	folio_set_waiters(folio);
1241	if (!folio_trylock_flag(folio, bit_nr, wait))
1242	__add_wait_queue_entry_tail(wq_head: q, wq_entry: wait);
1243	spin_unlock_irq(lock: &q->lock);
1244
1245	/*
1246	* From now on, all the logic will be based on
1247	* the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to
1248	* see whether the page bit testing has already
1249	* been done by the wake function.
1250	*
1251	* We can drop our reference to the folio.
1252	*/
1253	if (behavior == DROP)
1254	folio_put(folio);
1255
1256	/*
1257	* Note that until the "finish_wait()", or until
1258	* we see the WQ_FLAG_WOKEN flag, we need to
1259	* be very careful with the 'wait->flags', because
1260	* we may race with a waker that sets them.
1261	*/
1262	for (;;) {
1263	unsigned int flags;
1264
1265	set_current_state(state);
1266
1267	/* Loop until we've been woken or interrupted */
1268	flags = smp_load_acquire(&wait->flags);
1269	if (!(flags & WQ_FLAG_WOKEN)) {
1270	if (signal_pending_state(state, current))
1271	break;
1272
1273	io_schedule();
1274	continue;
1275	}
1276
1277	/* If we were non-exclusive, we're done */
1278	if (behavior != EXCLUSIVE)
1279	break;
1280
1281	/* If the waker got the lock for us, we're done */
1282	if (flags & WQ_FLAG_DONE)
1283	break;
1284
1285	/*
1286	* Otherwise, if we're getting the lock, we need to
1287	* try to get it ourselves.
1288	*
1289	* And if that fails, we'll have to retry this all.
1290	*/
1291	if (unlikely(test_and_set_bit(bit_nr, folio_flags(folio, 0))))
1292	goto repeat;
1293
1294	wait->flags |= WQ_FLAG_DONE;
1295	break;
1296	}
1297
1298	/*
1299	* If a signal happened, this 'finish_wait()' may remove the last
1300	* waiter from the wait-queues, but the folio waiters bit will remain
1301	* set. That's ok. The next wakeup will take care of it, and trying
1302	* to do it here would be difficult and prone to races.
1303	*/
1304	finish_wait(wq_head: q, wq_entry: wait);
1305
1306	if (thrashing) {
1307	delayacct_thrashing_end(in_thrashing: &in_thrashing);
1308	psi_memstall_leave(flags: &pflags);
1309	}
1310
1311	/*
1312	* NOTE! The wait->flags weren't stable until we've done the
1313	* 'finish_wait()', and we could have exited the loop above due
1314	* to a signal, and had a wakeup event happen after the signal
1315	* test but before the 'finish_wait()'.
1316	*
1317	* So only after the finish_wait() can we reliably determine
1318	* if we got woken up or not, so we can now figure out the final
1319	* return value based on that state without races.
1320	*
1321	* Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive
1322	* waiter, but an exclusive one requires WQ_FLAG_DONE.
1323	*/
1324	if (behavior == EXCLUSIVE)
1325	return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR;
1326
1327	return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
1328	}
1329
1330	#ifdef CONFIG_MIGRATION
1331	/**
1332	* migration_entry_wait_on_locked - Wait for a migration entry to be removed
1333	* @entry: migration swap entry.
1334	* @ptl: already locked ptl. This function will drop the lock.
1335	*
1336	* Wait for a migration entry referencing the given page to be removed. This is
1337	* equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except
1338	* this can be called without taking a reference on the page. Instead this
1339	* should be called while holding the ptl for the migration entry referencing
1340	* the page.
1341	*
1342	* Returns after unlocking the ptl.
1343	*
1344	* This follows the same logic as folio_wait_bit_common() so see the comments
1345	* there.
1346	*/
1347	void migration_entry_wait_on_locked(swp_entry_t entry, spinlock_t *ptl)
1348	__releases(ptl)
1349	{
1350	struct wait_page_queue wait_page;
1351	wait_queue_entry_t *wait = &wait_page.wait;
1352	bool thrashing = false;
1353	unsigned long pflags;
1354	bool in_thrashing;
1355	wait_queue_head_t *q;
1356	struct folio *folio = page_folio(pfn_swap_entry_to_page(entry));
1357
1358	q = folio_waitqueue(folio);
1359	if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
1360	delayacct_thrashing_start(in_thrashing: &in_thrashing);
1361	psi_memstall_enter(flags: &pflags);
1362	thrashing = true;
1363	}
1364
1365	init_wait(wait);
1366	wait->func = wake_page_function;
1367	wait_page.folio = folio;
1368	wait_page.bit_nr = PG_locked;
1369	wait->flags = 0;
1370
1371	spin_lock_irq(lock: &q->lock);
1372	folio_set_waiters(folio);
1373	if (!folio_trylock_flag(folio, bit_nr: PG_locked, wait))
1374	__add_wait_queue_entry_tail(wq_head: q, wq_entry: wait);
1375	spin_unlock_irq(lock: &q->lock);
1376
1377	/*
1378	* If a migration entry exists for the page the migration path must hold
1379	* a valid reference to the page, and it must take the ptl to remove the
1380	* migration entry. So the page is valid until the ptl is dropped.
1381	*/
1382	spin_unlock(lock: ptl);
1383
1384	for (;;) {
1385	unsigned int flags;
1386
1387	set_current_state(TASK_UNINTERRUPTIBLE);
1388
1389	/* Loop until we've been woken or interrupted */
1390	flags = smp_load_acquire(&wait->flags);
1391	if (!(flags & WQ_FLAG_WOKEN)) {
1392	if (signal_pending_state(TASK_UNINTERRUPTIBLE, current))
1393	break;
1394
1395	io_schedule();
1396	continue;
1397	}
1398	break;
1399	}
1400
1401	finish_wait(wq_head: q, wq_entry: wait);
1402
1403	if (thrashing) {
1404	delayacct_thrashing_end(in_thrashing: &in_thrashing);
1405	psi_memstall_leave(flags: &pflags);
1406	}
1407	}
1408	#endif
1409
1410	void folio_wait_bit(struct folio *folio, int bit_nr)
1411	{
1412	folio_wait_bit_common(folio, bit_nr, TASK_UNINTERRUPTIBLE, behavior: SHARED);
1413	}
1414	EXPORT_SYMBOL(folio_wait_bit);
1415
1416	int folio_wait_bit_killable(struct folio *folio, int bit_nr)
1417	{
1418	return folio_wait_bit_common(folio, bit_nr, TASK_KILLABLE, behavior: SHARED);
1419	}
1420	EXPORT_SYMBOL(folio_wait_bit_killable);
1421
1422	/**
1423	* folio_put_wait_locked - Drop a reference and wait for it to be unlocked
1424	* @folio: The folio to wait for.
1425	* @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc).
1426	*
1427	* The caller should hold a reference on @folio. They expect the page to
1428	* become unlocked relatively soon, but do not wish to hold up migration
1429	* (for example) by holding the reference while waiting for the folio to
1430	* come unlocked. After this function returns, the caller should not
1431	* dereference @folio.
1432	*
1433	* Return: 0 if the folio was unlocked or -EINTR if interrupted by a signal.
1434	*/
1435	static int folio_put_wait_locked(struct folio *folio, int state)
1436	{
1437	return folio_wait_bit_common(folio, bit_nr: PG_locked, state, behavior: DROP);
1438	}
1439
1440	/**
1441	* folio_add_wait_queue - Add an arbitrary waiter to a folio's wait queue
1442	* @folio: Folio defining the wait queue of interest
1443	* @waiter: Waiter to add to the queue
1444	*
1445	* Add an arbitrary @waiter to the wait queue for the nominated @folio.
1446	*/
1447	void folio_add_wait_queue(struct folio *folio, wait_queue_entry_t *waiter)
1448	{
1449	wait_queue_head_t *q = folio_waitqueue(folio);
1450	unsigned long flags;
1451
1452	spin_lock_irqsave(&q->lock, flags);
1453	__add_wait_queue_entry_tail(wq_head: q, wq_entry: waiter);
1454	folio_set_waiters(folio);
1455	spin_unlock_irqrestore(lock: &q->lock, flags);
1456	}
1457	EXPORT_SYMBOL_GPL(folio_add_wait_queue);
1458
1459	/**
1460	* folio_unlock - Unlock a locked folio.
1461	* @folio: The folio.
1462	*
1463	* Unlocks the folio and wakes up any thread sleeping on the page lock.
1464	*
1465	* Context: May be called from interrupt or process context. May not be
1466	* called from NMI context.
1467	*/
1468	void folio_unlock(struct folio *folio)
1469	{
1470	/* Bit 7 allows x86 to check the byte's sign bit */
1471	BUILD_BUG_ON(PG_waiters != 7);
1472	BUILD_BUG_ON(PG_locked > 7);
1473	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1474	if (folio_xor_flags_has_waiters(folio, mask: 1 << PG_locked))
1475	folio_wake_bit(folio, bit_nr: PG_locked);
1476	}
1477	EXPORT_SYMBOL(folio_unlock);
1478
1479	/**
1480	* folio_end_read - End read on a folio.
1481	* @folio: The folio.
1482	* @success: True if all reads completed successfully.
1483	*
1484	* When all reads against a folio have completed, filesystems should
1485	* call this function to let the pagecache know that no more reads
1486	* are outstanding. This will unlock the folio and wake up any thread
1487	* sleeping on the lock. The folio will also be marked uptodate if all
1488	* reads succeeded.
1489	*
1490	* Context: May be called from interrupt or process context. May not be
1491	* called from NMI context.
1492	*/
1493	void folio_end_read(struct folio *folio, bool success)
1494	{
1495	unsigned long mask = 1 << PG_locked;
1496
1497	/* Must be in bottom byte for x86 to work */
1498	BUILD_BUG_ON(PG_uptodate > 7);
1499	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1500	VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);
1501
1502	if (likely(success))
1503	mask |= 1 << PG_uptodate;
1504	if (folio_xor_flags_has_waiters(folio, mask))
1505	folio_wake_bit(folio, bit_nr: PG_locked);
1506	}
1507	EXPORT_SYMBOL(folio_end_read);
1508
1509	/**
1510	* folio_end_private_2 - Clear PG_private_2 and wake any waiters.
1511	* @folio: The folio.
1512	*
1513	* Clear the PG_private_2 bit on a folio and wake up any sleepers waiting for
1514	* it. The folio reference held for PG_private_2 being set is released.
1515	*
1516	* This is, for example, used when a netfs folio is being written to a local
1517	* disk cache, thereby allowing writes to the cache for the same folio to be
1518	* serialised.
1519	*/
1520	void folio_end_private_2(struct folio *folio)
1521	{
1522	VM_BUG_ON_FOLIO(!folio_test_private_2(folio), folio);
1523	clear_bit_unlock(nr: PG_private_2, addr: folio_flags(folio, n: 0));
1524	folio_wake_bit(folio, bit_nr: PG_private_2);
1525	folio_put(folio);
1526	}
1527	EXPORT_SYMBOL(folio_end_private_2);
1528
1529	/**
1530	* folio_wait_private_2 - Wait for PG_private_2 to be cleared on a folio.
1531	* @folio: The folio to wait on.
1532	*
1533	* Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio.
1534	*/
1535	void folio_wait_private_2(struct folio *folio)
1536	{
1537	while (folio_test_private_2(folio))
1538	folio_wait_bit(folio, PG_private_2);
1539	}
1540	EXPORT_SYMBOL(folio_wait_private_2);
1541
1542	/**
1543	* folio_wait_private_2_killable - Wait for PG_private_2 to be cleared on a folio.
1544	* @folio: The folio to wait on.
1545	*
1546	* Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio or until a
1547	* fatal signal is received by the calling task.
1548	*
1549	* Return:
1550	* - 0 if successful.
1551	* - -EINTR if a fatal signal was encountered.
1552	*/
1553	int folio_wait_private_2_killable(struct folio *folio)
1554	{
1555	int ret = 0;
1556
1557	while (folio_test_private_2(folio)) {
1558	ret = folio_wait_bit_killable(folio, PG_private_2);
1559	if (ret < 0)
1560	break;
1561	}
1562
1563	return ret;
1564	}
1565	EXPORT_SYMBOL(folio_wait_private_2_killable);
1566
1567	/**
1568	* folio_end_writeback - End writeback against a folio.
1569	* @folio: The folio.
1570	*
1571	* The folio must actually be under writeback.
1572	*
1573	* Context: May be called from process or interrupt context.
1574	*/
1575	void folio_end_writeback(struct folio *folio)
1576	{
1577	VM_BUG_ON_FOLIO(!folio_test_writeback(folio), folio);
1578
1579	/*
1580	* folio_test_clear_reclaim() could be used here but it is an
1581	* atomic operation and overkill in this particular case. Failing
1582	* to shuffle a folio marked for immediate reclaim is too mild
1583	* a gain to justify taking an atomic operation penalty at the
1584	* end of every folio writeback.
1585	*/
1586	if (folio_test_reclaim(folio)) {
1587	folio_clear_reclaim(folio);
1588	folio_rotate_reclaimable(folio);
1589	}
1590
1591	/*
1592	* Writeback does not hold a folio reference of its own, relying
1593	* on truncation to wait for the clearing of PG_writeback.
1594	* But here we must make sure that the folio is not freed and
1595	* reused before the folio_wake_bit().
1596	*/
1597	folio_get(folio);
1598	if (__folio_end_writeback(folio))
1599	folio_wake_bit(folio, bit_nr: PG_writeback);
1600	acct_reclaim_writeback(folio);
1601	folio_put(folio);
1602	}
1603	EXPORT_SYMBOL(folio_end_writeback);
1604
1605	/**
1606	* __folio_lock - Get a lock on the folio, assuming we need to sleep to get it.
1607	* @folio: The folio to lock
1608	*/
1609	void __folio_lock(struct folio *folio)
1610	{
1611	folio_wait_bit_common(folio, bit_nr: PG_locked, TASK_UNINTERRUPTIBLE,
1612	behavior: EXCLUSIVE);
1613	}
1614	EXPORT_SYMBOL(__folio_lock);
1615
1616	int __folio_lock_killable(struct folio *folio)
1617	{
1618	return folio_wait_bit_common(folio, bit_nr: PG_locked, TASK_KILLABLE,
1619	behavior: EXCLUSIVE);
1620	}
1621	EXPORT_SYMBOL_GPL(__folio_lock_killable);
1622
1623	static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
1624	{
1625	struct wait_queue_head *q = folio_waitqueue(folio);
1626	int ret = 0;
1627
1628	wait->folio = folio;
1629	wait->bit_nr = PG_locked;
1630
1631	spin_lock_irq(lock: &q->lock);
1632	__add_wait_queue_entry_tail(wq_head: q, wq_entry: &wait->wait);
1633	folio_set_waiters(folio);
1634	ret = !folio_trylock(folio);
1635	/*
1636	* If we were successful now, we know we're still on the
1637	* waitqueue as we're still under the lock. This means it's
1638	* safe to remove and return success, we know the callback
1639	* isn't going to trigger.
1640	*/
1641	if (!ret)
1642	__remove_wait_queue(wq_head: q, wq_entry: &wait->wait);
1643	else
1644	ret = -EIOCBQUEUED;
1645	spin_unlock_irq(lock: &q->lock);
1646	return ret;
1647	}
1648
1649	/*
1650	* Return values:
1651	* 0 - folio is locked.
1652	* non-zero - folio is not locked.
1653	* mmap_lock or per-VMA lock has been released (mmap_read_unlock() or
1654	* vma_end_read()), unless flags had both FAULT_FLAG_ALLOW_RETRY and
1655	* FAULT_FLAG_RETRY_NOWAIT set, in which case the lock is still held.
1656	*
1657	* If neither ALLOW_RETRY nor KILLABLE are set, will always return 0
1658	* with the folio locked and the mmap_lock/per-VMA lock is left unperturbed.
1659	*/
1660	vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf)
1661	{
1662	unsigned int flags = vmf->flags;
1663
1664	if (fault_flag_allow_retry_first(flags)) {
1665	/*
1666	* CAUTION! In this case, mmap_lock/per-VMA lock is not
1667	* released even though returning VM_FAULT_RETRY.
1668	*/
1669	if (flags & FAULT_FLAG_RETRY_NOWAIT)
1670	return VM_FAULT_RETRY;
1671
1672	release_fault_lock(vmf);
1673	if (flags & FAULT_FLAG_KILLABLE)
1674	folio_wait_locked_killable(folio);
1675	else
1676	folio_wait_locked(folio);
1677	return VM_FAULT_RETRY;
1678	}
1679	if (flags & FAULT_FLAG_KILLABLE) {
1680	bool ret;
1681
1682	ret = __folio_lock_killable(folio);
1683	if (ret) {
1684	release_fault_lock(vmf);
1685	return VM_FAULT_RETRY;
1686	}
1687	} else {
1688	__folio_lock(folio);
1689	}
1690
1691	return 0;
1692	}
1693
1694	/**
1695	* page_cache_next_miss() - Find the next gap in the page cache.
1696	* @mapping: Mapping.
1697	* @index: Index.
1698	* @max_scan: Maximum range to search.
1699	*
1700	* Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
1701	* gap with the lowest index.
1702	*
1703	* This function may be called under the rcu_read_lock. However, this will
1704	* not atomically search a snapshot of the cache at a single point in time.
1705	* For example, if a gap is created at index 5, then subsequently a gap is
1706	* created at index 10, page_cache_next_miss covering both indices may
1707	* return 10 if called under the rcu_read_lock.
1708	*
1709	* Return: The index of the gap if found, otherwise an index outside the
1710	* range specified (in which case 'return - index >= max_scan' will be true).
1711	* In the rare case of index wrap-around, 0 will be returned.
1712	*/
1713	pgoff_t page_cache_next_miss(struct address_space *mapping,
1714	pgoff_t index, unsigned long max_scan)
1715	{
1716	XA_STATE(xas, &mapping->i_pages, index);
1717
1718	while (max_scan--) {
1719	void *entry = xas_next(xas: &xas);
1720	if (!entry || xa_is_value(entry))
1721	break;
1722	if (xas.xa_index == 0)
1723	break;
1724	}
1725
1726	return xas.xa_index;
1727	}
1728	EXPORT_SYMBOL(page_cache_next_miss);
1729
1730	/**
1731	* page_cache_prev_miss() - Find the previous gap in the page cache.
1732	* @mapping: Mapping.
1733	* @index: Index.
1734	* @max_scan: Maximum range to search.
1735	*
1736	* Search the range [max(index - max_scan + 1, 0), index] for the
1737	* gap with the highest index.
1738	*
1739	* This function may be called under the rcu_read_lock. However, this will
1740	* not atomically search a snapshot of the cache at a single point in time.
1741	* For example, if a gap is created at index 10, then subsequently a gap is
1742	* created at index 5, page_cache_prev_miss() covering both indices may
1743	* return 5 if called under the rcu_read_lock.
1744	*
1745	* Return: The index of the gap if found, otherwise an index outside the
1746	* range specified (in which case 'index - return >= max_scan' will be true).
1747	* In the rare case of wrap-around, ULONG_MAX will be returned.
1748	*/
1749	pgoff_t page_cache_prev_miss(struct address_space *mapping,
1750	pgoff_t index, unsigned long max_scan)
1751	{
1752	XA_STATE(xas, &mapping->i_pages, index);
1753
1754	while (max_scan--) {
1755	void *entry = xas_prev(xas: &xas);
1756	if (!entry || xa_is_value(entry))
1757	break;
1758	if (xas.xa_index == ULONG_MAX)
1759	break;
1760	}
1761
1762	return xas.xa_index;
1763	}
1764	EXPORT_SYMBOL(page_cache_prev_miss);
1765
1766	/*
1767	* Lockless page cache protocol:
1768	* On the lookup side:
1769	* 1. Load the folio from i_pages
1770	* 2. Increment the refcount if it's not zero
1771	* 3. If the folio is not found by xas_reload(), put the refcount and retry
1772	*
1773	* On the removal side:
1774	* A. Freeze the page (by zeroing the refcount if nobody else has a reference)
1775	* B. Remove the page from i_pages
1776	* C. Return the page to the page allocator
1777	*
1778	* This means that any page may have its reference count temporarily
1779	* increased by a speculative page cache (or fast GUP) lookup as it can
1780	* be allocated by another user before the RCU grace period expires.
1781	* Because the refcount temporarily acquired here may end up being the
1782	* last refcount on the page, any page allocation must be freeable by
1783	* folio_put().
1784	*/
1785
1786	/*
1787	* filemap_get_entry - Get a page cache entry.
1788	* @mapping: the address_space to search
1789	* @index: The page cache index.
1790	*
1791	* Looks up the page cache entry at @mapping & @index. If it is a folio,
1792	* it is returned with an increased refcount. If it is a shadow entry
1793	* of a previously evicted folio, or a swap entry from shmem/tmpfs,
1794	* it is returned without further action.
1795	*
1796	* Return: The folio, swap or shadow entry, %NULL if nothing is found.
1797	*/
1798	void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
1799	{
1800	XA_STATE(xas, &mapping->i_pages, index);
1801	struct folio *folio;
1802
1803	rcu_read_lock();
1804	repeat:
1805	xas_reset(xas: &xas);
1806	folio = xas_load(&xas);
1807	if (xas_retry(xas: &xas, entry: folio))
1808	goto repeat;
1809	/*
1810	* A shadow entry of a recently evicted page, or a swap entry from
1811	* shmem/tmpfs. Return it without attempting to raise page count.
1812	*/
1813	if (!folio || xa_is_value(entry: folio))
1814	goto out;
1815
1816	if (!folio_try_get_rcu(folio))
1817	goto repeat;
1818
1819	if (unlikely(folio != xas_reload(&xas))) {
1820	folio_put(folio);
1821	goto repeat;
1822	}
1823	out:
1824	rcu_read_unlock();
1825
1826	return folio;
1827	}
1828
1829	/**
1830	* __filemap_get_folio - Find and get a reference to a folio.
1831	* @mapping: The address_space to search.
1832	* @index: The page index.
1833	* @fgp_flags: %FGP flags modify how the folio is returned.
1834	* @gfp: Memory allocation flags to use if %FGP_CREAT is specified.
1835	*
1836	* Looks up the page cache entry at @mapping & @index.
1837	*
1838	* If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
1839	* if the %GFP flags specified for %FGP_CREAT are atomic.
1840	*
1841	* If this function returns a folio, it is returned with an increased refcount.
1842	*
1843	* Return: The found folio or an ERR_PTR() otherwise.
1844	*/
1845	struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
1846	fgf_t fgp_flags, gfp_t gfp)
1847	{
1848	struct folio *folio;
1849
1850	repeat:
1851	folio = filemap_get_entry(mapping, index);
1852	if (xa_is_value(entry: folio))
1853	folio = NULL;
1854	if (!folio)
1855	goto no_page;
1856
1857	if (fgp_flags & FGP_LOCK) {
1858	if (fgp_flags & FGP_NOWAIT) {
1859	if (!folio_trylock(folio)) {
1860	folio_put(folio);
1861	return ERR_PTR(error: -EAGAIN);
1862	}
1863	} else {
1864	folio_lock(folio);
1865	}
1866
1867	/* Has the page been truncated? */
1868	if (unlikely(folio->mapping != mapping)) {
1869	folio_unlock(folio);
1870	folio_put(folio);
1871	goto repeat;
1872	}
1873	VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
1874	}
1875
1876	if (fgp_flags & FGP_ACCESSED)
1877	folio_mark_accessed(folio);
1878	else if (fgp_flags & FGP_WRITE) {
1879	/* Clear idle flag for buffer write */
1880	if (folio_test_idle(folio))
1881	folio_clear_idle(folio);
1882	}
1883
1884	if (fgp_flags & FGP_STABLE)
1885	folio_wait_stable(folio);
1886	no_page:
1887	if (!folio && (fgp_flags & FGP_CREAT)) {
1888	unsigned order = FGF_GET_ORDER(fgp_flags);
1889	int err;
1890
1891	if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
1892	gfp |= __GFP_WRITE;
1893	if (fgp_flags & FGP_NOFS)
1894	gfp &= ~__GFP_FS;
1895	if (fgp_flags & FGP_NOWAIT) {
1896	gfp &= ~GFP_KERNEL;
1897	gfp |= GFP_NOWAIT | __GFP_NOWARN;
1898	}
1899	if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
1900	fgp_flags |= FGP_LOCK;
1901
1902	if (!mapping_large_folio_support(mapping))
1903	order = 0;
1904	if (order > MAX_PAGECACHE_ORDER)
1905	order = MAX_PAGECACHE_ORDER;
1906	/* If we're not aligned, allocate a smaller folio */
1907	if (index & ((1UL << order) - 1))
1908	order = __ffs(index);
1909
1910	do {
1911	gfp_t alloc_gfp = gfp;
1912
1913	err = -ENOMEM;
1914	if (order == 1)
1915	order = 0;
1916	if (order > 0)
1917	alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN;
1918	folio = filemap_alloc_folio(alloc_gfp, order);
1919	if (!folio)
1920	continue;
1921
1922	/* Init accessed so avoid atomic mark_page_accessed later */
1923	if (fgp_flags & FGP_ACCESSED)
1924	__folio_set_referenced(folio);
1925
1926	err = filemap_add_folio(mapping, folio, index, gfp);
1927	if (!err)
1928	break;
1929	folio_put(folio);
1930	folio = NULL;
1931	} while (order-- > 0);
1932
1933	if (err == -EEXIST)
1934	goto repeat;
1935	if (err)
1936	return ERR_PTR(error: err);
1937	/*
1938	* filemap_add_folio locks the page, and for mmap
1939	* we expect an unlocked page.
1940	*/
1941	if (folio && (fgp_flags & FGP_FOR_MMAP))
1942	folio_unlock(folio);
1943	}
1944
1945	if (!folio)
1946	return ERR_PTR(error: -ENOENT);
1947	return folio;
1948	}
1949	EXPORT_SYMBOL(__filemap_get_folio);
1950
1951	static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max,
1952	xa_mark_t mark)
1953	{
1954	struct folio *folio;
1955
1956	retry:
1957	if (mark == XA_PRESENT)
1958	folio = xas_find(xas, max);
1959	else
1960	folio = xas_find_marked(xas, max, mark);
1961
1962	if (xas_retry(xas, entry: folio))
1963	goto retry;
1964	/*
1965	* A shadow entry of a recently evicted page, a swap
1966	* entry from shmem/tmpfs or a DAX entry. Return it
1967	* without attempting to raise page count.
1968	*/
1969	if (!folio || xa_is_value(entry: folio))
1970	return folio;
1971
1972	if (!folio_try_get_rcu(folio))
1973	goto reset;
1974
1975	if (unlikely(folio != xas_reload(xas))) {
1976	folio_put(folio);
1977	goto reset;
1978	}
1979
1980	return folio;
1981	reset:
1982	xas_reset(xas);
1983	goto retry;
1984	}
1985
1986	/**
1987	* find_get_entries - gang pagecache lookup
1988	* @mapping: The address_space to search
1989	* @start: The starting page cache index
1990	* @end: The final page index (inclusive).
1991	* @fbatch: Where the resulting entries are placed.
1992	* @indices: The cache indices corresponding to the entries in @entries
1993	*
1994	* find_get_entries() will search for and return a batch of entries in
1995	* the mapping. The entries are placed in @fbatch. find_get_entries()
1996	* takes a reference on any actual folios it returns.
1997	*
1998	* The entries have ascending indexes. The indices may not be consecutive
1999	* due to not-present entries or large folios.
2000	*
2001	* Any shadow entries of evicted folios, or swap entries from
2002	* shmem/tmpfs, are included in the returned array.
2003	*
2004	* Return: The number of entries which were found.
2005	*/
2006	unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
2007	pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
2008	{
2009	XA_STATE(xas, &mapping->i_pages, *start);
2010	struct folio *folio;
2011
2012	rcu_read_lock();
2013	while ((folio = find_get_entry(xas: &xas, max: end, XA_PRESENT)) != NULL) {
2014	indices[fbatch->nr] = xas.xa_index;
2015	if (!folio_batch_add(fbatch, folio))
2016	break;
2017	}
2018	rcu_read_unlock();
2019
2020	if (folio_batch_count(fbatch)) {
2021	unsigned long nr = 1;
2022	int idx = folio_batch_count(fbatch) - 1;
2023
2024	folio = fbatch->folios[idx];
2025	if (!xa_is_value(entry: folio))
2026	nr = folio_nr_pages(folio);
2027	*start = indices[idx] + nr;
2028	}
2029	return folio_batch_count(fbatch);
2030	}
2031
2032	/**
2033	* find_lock_entries - Find a batch of pagecache entries.
2034	* @mapping: The address_space to search.
2035	* @start: The starting page cache index.
2036	* @end: The final page index (inclusive).
2037	* @fbatch: Where the resulting entries are placed.
2038	* @indices: The cache indices of the entries in @fbatch.
2039	*
2040	* find_lock_entries() will return a batch of entries from @mapping.
2041	* Swap, shadow and DAX entries are included. Folios are returned
2042	* locked and with an incremented refcount. Folios which are locked
2043	* by somebody else or under writeback are skipped. Folios which are
2044	* partially outside the range are not returned.
2045	*
2046	* The entries have ascending indexes. The indices may not be consecutive
2047	* due to not-present entries, large folios, folios which could not be
2048	* locked or folios under writeback.
2049	*
2050	* Return: The number of entries which were found.
2051	*/
2052	unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start,
2053	pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
2054	{
2055	XA_STATE(xas, &mapping->i_pages, *start);
2056	struct folio *folio;
2057
2058	rcu_read_lock();
2059	while ((folio = find_get_entry(xas: &xas, max: end, XA_PRESENT))) {
2060	if (!xa_is_value(entry: folio)) {
2061	if (folio->index < *start)
2062	goto put;
2063	if (folio_next_index(folio) - 1 > end)
2064	goto put;
2065	if (!folio_trylock(folio))
2066	goto put;
2067	if (folio->mapping != mapping ||
2068	folio_test_writeback(folio))
2069	goto unlock;
2070	VM_BUG_ON_FOLIO(!folio_contains(folio, xas.xa_index),
2071	folio);
2072	}
2073	indices[fbatch->nr] = xas.xa_index;
2074	if (!folio_batch_add(fbatch, folio))
2075	break;
2076	continue;
2077	unlock:
2078	folio_unlock(folio);
2079	put:
2080	folio_put(folio);
2081	}
2082	rcu_read_unlock();
2083
2084	if (folio_batch_count(fbatch)) {
2085	unsigned long nr = 1;
2086	int idx = folio_batch_count(fbatch) - 1;
2087
2088	folio = fbatch->folios[idx];
2089	if (!xa_is_value(entry: folio))
2090	nr = folio_nr_pages(folio);
2091	*start = indices[idx] + nr;
2092	}
2093	return folio_batch_count(fbatch);
2094	}
2095
2096	/**
2097	* filemap_get_folios - Get a batch of folios
2098	* @mapping: The address_space to search
2099	* @start: The starting page index
2100	* @end: The final page index (inclusive)
2101	* @fbatch: The batch to fill.
2102	*
2103	* Search for and return a batch of folios in the mapping starting at
2104	* index @start and up to index @end (inclusive). The folios are returned
2105	* in @fbatch with an elevated reference count.
2106	*
2107	* Return: The number of folios which were found.
2108	* We also update @start to index the next folio for the traversal.
2109	*/
2110	unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
2111	pgoff_t end, struct folio_batch *fbatch)
2112	{
2113	return filemap_get_folios_tag(mapping, start, end, XA_PRESENT, fbatch);
2114	}
2115	EXPORT_SYMBOL(filemap_get_folios);
2116
2117	/**
2118	* filemap_get_folios_contig - Get a batch of contiguous folios
2119	* @mapping: The address_space to search
2120	* @start: The starting page index
2121	* @end: The final page index (inclusive)
2122	* @fbatch: The batch to fill
2123	*
2124	* filemap_get_folios_contig() works exactly like filemap_get_folios(),
2125	* except the returned folios are guaranteed to be contiguous. This may
2126	* not return all contiguous folios if the batch gets filled up.
2127	*
2128	* Return: The number of folios found.
2129	* Also update @start to be positioned for traversal of the next folio.
2130	*/
2131
2132	unsigned filemap_get_folios_contig(struct address_space *mapping,
2133	pgoff_t *start, pgoff_t end, struct folio_batch *fbatch)
2134	{
2135	XA_STATE(xas, &mapping->i_pages, *start);
2136	unsigned long nr;
2137	struct folio *folio;
2138
2139	rcu_read_lock();
2140
2141	for (folio = xas_load(&xas); folio && xas.xa_index <= end;
2142	folio = xas_next(xas: &xas)) {
2143	if (xas_retry(xas: &xas, entry: folio))
2144	continue;
2145	/*
2146	* If the entry has been swapped out, we can stop looking.
2147	* No current caller is looking for DAX entries.
2148	*/
2149	if (xa_is_value(entry: folio))
2150	goto update_start;
2151
2152	if (!folio_try_get_rcu(folio))
2153	goto retry;
2154
2155	if (unlikely(folio != xas_reload(&xas)))
2156	goto put_folio;
2157
2158	if (!folio_batch_add(fbatch, folio)) {
2159	nr = folio_nr_pages(folio);
2160	*start = folio->index + nr;
2161	goto out;
2162	}
2163	continue;
2164	put_folio:
2165	folio_put(folio);
2166
2167	retry:
2168	xas_reset(xas: &xas);
2169	}
2170
2171	update_start:
2172	nr = folio_batch_count(fbatch);
2173
2174	if (nr) {
2175	folio = fbatch->folios[nr - 1];
2176	*start = folio->index + folio_nr_pages(folio);
2177	}
2178	out:
2179	rcu_read_unlock();
2180	return folio_batch_count(fbatch);
2181	}
2182	EXPORT_SYMBOL(filemap_get_folios_contig);
2183
2184	/**
2185	* filemap_get_folios_tag - Get a batch of folios matching @tag
2186	* @mapping: The address_space to search
2187	* @start: The starting page index
2188	* @end: The final page index (inclusive)
2189	* @tag: The tag index
2190	* @fbatch: The batch to fill
2191	*
2192	* The first folio may start before @start; if it does, it will contain
2193	* @start. The final folio may extend beyond @end; if it does, it will
2194	* contain @end. The folios have ascending indices. There may be gaps
2195	* between the folios if there are indices which have no folio in the
2196	* page cache. If folios are added to or removed from the page cache
2197	* while this is running, they may or may not be found by this call.
2198	* Only returns folios that are tagged with @tag.
2199	*
2200	* Return: The number of folios found.
2201	* Also update @start to index the next folio for traversal.
2202	*/
2203	unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start,
2204	pgoff_t end, xa_mark_t tag, struct folio_batch *fbatch)
2205	{
2206	XA_STATE(xas, &mapping->i_pages, *start);
2207	struct folio *folio;
2208
2209	rcu_read_lock();
2210	while ((folio = find_get_entry(xas: &xas, max: end, mark: tag)) != NULL) {
2211	/*
2212	* Shadow entries should never be tagged, but this iteration
2213	* is lockless so there is a window for page reclaim to evict
2214	* a page we saw tagged. Skip over it.
2215	*/
2216	if (xa_is_value(entry: folio))
2217	continue;
2218	if (!folio_batch_add(fbatch, folio)) {
2219	unsigned long nr = folio_nr_pages(folio);
2220	*start = folio->index + nr;
2221	goto out;
2222	}
2223	}
2224	/*
2225	* We come here when there is no page beyond @end. We take care to not
2226	* overflow the index @start as it confuses some of the callers. This
2227	* breaks the iteration when there is a page at index -1 but that is
2228	* already broke anyway.
2229	*/
2230	if (end == (pgoff_t)-1)
2231	*start = (pgoff_t)-1;
2232	else
2233	*start = end + 1;
2234	out:
2235	rcu_read_unlock();
2236
2237	return folio_batch_count(fbatch);
2238	}
2239	EXPORT_SYMBOL(filemap_get_folios_tag);
2240
2241	/*
2242	* CD/DVDs are error prone. When a medium error occurs, the driver may fail
2243	* a _large_ part of the i/o request. Imagine the worst scenario:
2244	*
2245	* ---R__________________________________________B__________
2246	* ^ reading here ^ bad block(assume 4k)
2247	*
2248	* read(R) => miss => readahead(R...B) => media error => frustrating retries
2249	* => failing the whole request => read(R) => read(R+1) =>
2250	* readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
2251	* readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
2252	* readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
2253	*
2254	* It is going insane. Fix it by quickly scaling down the readahead size.
2255	*/
2256	static void shrink_readahead_size_eio(struct file_ra_state *ra)
2257	{
2258	ra->ra_pages /= 4;
2259	}
2260
2261	/*
2262	* filemap_get_read_batch - Get a batch of folios for read
2263	*
2264	* Get a batch of folios which represent a contiguous range of bytes in
2265	* the file. No exceptional entries will be returned. If @index is in
2266	* the middle of a folio, the entire folio will be returned. The last
2267	* folio in the batch may have the readahead flag set or the uptodate flag
2268	* clear so that the caller can take the appropriate action.
2269	*/
2270	static void filemap_get_read_batch(struct address_space *mapping,
2271	pgoff_t index, pgoff_t max, struct folio_batch *fbatch)
2272	{
2273	XA_STATE(xas, &mapping->i_pages, index);
2274	struct folio *folio;
2275
2276	rcu_read_lock();
2277	for (folio = xas_load(&xas); folio; folio = xas_next(xas: &xas)) {
2278	if (xas_retry(xas: &xas, entry: folio))
2279	continue;
2280	if (xas.xa_index > max || xa_is_value(entry: folio))
2281	break;
2282	if (xa_is_sibling(entry: folio))
2283	break;
2284	if (!folio_try_get_rcu(folio))
2285	goto retry;
2286
2287	if (unlikely(folio != xas_reload(&xas)))
2288	goto put_folio;
2289
2290	if (!folio_batch_add(fbatch, folio))
2291	break;
2292	if (!folio_test_uptodate(folio))
2293	break;
2294	if (folio_test_readahead(folio))
2295	break;
2296	xas_advance(xas: &xas, index: folio_next_index(folio) - 1);
2297	continue;
2298	put_folio:
2299	folio_put(folio);
2300	retry:
2301	xas_reset(xas: &xas);
2302	}
2303	rcu_read_unlock();
2304	}
2305
2306	static int filemap_read_folio(struct file *file, filler_t filler,
2307	struct folio *folio)
2308	{
2309	bool workingset = folio_test_workingset(folio);
2310	unsigned long pflags;
2311	int error;
2312
2313	/*
2314	* A previous I/O error may have been due to temporary failures,
2315	* eg. multipath errors. PG_error will be set again if read_folio
2316	* fails.
2317	*/
2318	folio_clear_error(folio);
2319
2320	/* Start the actual read. The read will unlock the page. */
2321	if (unlikely(workingset))
2322	psi_memstall_enter(flags: &pflags);
2323	error = filler(file, folio);
2324	if (unlikely(workingset))
2325	psi_memstall_leave(flags: &pflags);
2326	if (error)
2327	return error;
2328
2329	error = folio_wait_locked_killable(folio);
2330	if (error)
2331	return error;
2332	if (folio_test_uptodate(folio))
2333	return 0;
2334	if (file)
2335	shrink_readahead_size_eio(ra: &file->f_ra);
2336	return -EIO;
2337	}
2338
2339	static bool filemap_range_uptodate(struct address_space *mapping,
2340	loff_t pos, size_t count, struct folio *folio,
2341	bool need_uptodate)
2342	{
2343	if (folio_test_uptodate(folio))
2344	return true;
2345	/* pipes can't handle partially uptodate pages */
2346	if (need_uptodate)
2347	return false;
2348	if (!mapping->a_ops->is_partially_uptodate)
2349	return false;
2350	if (mapping->host->i_blkbits >= folio_shift(folio))
2351	return false;
2352
2353	if (folio_pos(folio) > pos) {
2354	count -= folio_pos(folio) - pos;
2355	pos = 0;
2356	} else {
2357	pos -= folio_pos(folio);
2358	}
2359
2360	return mapping->a_ops->is_partially_uptodate(folio, pos, count);
2361	}
2362
2363	static int filemap_update_page(struct kiocb *iocb,
2364	struct address_space *mapping, size_t count,
2365	struct folio *folio, bool need_uptodate)
2366	{
2367	int error;
2368
2369	if (iocb->ki_flags & IOCB_NOWAIT) {
2370	if (!filemap_invalidate_trylock_shared(mapping))
2371	return -EAGAIN;
2372	} else {
2373	filemap_invalidate_lock_shared(mapping);
2374	}
2375
2376	if (!folio_trylock(folio)) {
2377	error = -EAGAIN;
2378	if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
2379	goto unlock_mapping;
2380	if (!(iocb->ki_flags & IOCB_WAITQ)) {
2381	filemap_invalidate_unlock_shared(mapping);
2382	/*
2383	* This is where we usually end up waiting for a
2384	* previously submitted readahead to finish.
2385	*/
2386	folio_put_wait_locked(folio, TASK_KILLABLE);
2387	return AOP_TRUNCATED_PAGE;
2388	}
2389	error = __folio_lock_async(folio, wait: iocb->ki_waitq);
2390	if (error)
2391	goto unlock_mapping;
2392	}
2393
2394	error = AOP_TRUNCATED_PAGE;
2395	if (!folio->mapping)
2396	goto unlock;
2397
2398	error = 0;
2399	if (filemap_range_uptodate(mapping, pos: iocb->ki_pos, count, folio,
2400	need_uptodate))
2401	goto unlock;
2402
2403	error = -EAGAIN;
2404	if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
2405	goto unlock;
2406
2407	error = filemap_read_folio(file: iocb->ki_filp, filler: mapping->a_ops->read_folio,
2408	folio);
2409	goto unlock_mapping;
2410	unlock:
2411	folio_unlock(folio);
2412	unlock_mapping:
2413	filemap_invalidate_unlock_shared(mapping);
2414	if (error == AOP_TRUNCATED_PAGE)
2415	folio_put(folio);
2416	return error;
2417	}
2418
2419	static int filemap_create_folio(struct file *file,
2420	struct address_space *mapping, pgoff_t index,
2421	struct folio_batch *fbatch)
2422	{
2423	struct folio *folio;
2424	int error;
2425
2426	folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
2427	if (!folio)
2428	return -ENOMEM;
2429
2430	/*
2431	* Protect against truncate / hole punch. Grabbing invalidate_lock
2432	* here assures we cannot instantiate and bring uptodate new
2433	* pagecache folios after evicting page cache during truncate
2434	* and before actually freeing blocks. Note that we could
2435	* release invalidate_lock after inserting the folio into
2436	* the page cache as the locked folio would then be enough to
2437	* synchronize with hole punching. But there are code paths
2438	* such as filemap_update_page() filling in partially uptodate
2439	* pages or ->readahead() that need to hold invalidate_lock
2440	* while mapping blocks for IO so let's hold the lock here as
2441	* well to keep locking rules simple.
2442	*/
2443	filemap_invalidate_lock_shared(mapping);
2444	error = filemap_add_folio(mapping, folio, index,
2445	mapping_gfp_constraint(mapping, GFP_KERNEL));
2446	if (error == -EEXIST)
2447	error = AOP_TRUNCATED_PAGE;
2448	if (error)
2449	goto error;
2450
2451	error = filemap_read_folio(file, filler: mapping->a_ops->read_folio, folio);
2452	if (error)
2453	goto error;
2454
2455	filemap_invalidate_unlock_shared(mapping);
2456	folio_batch_add(fbatch, folio);
2457	return 0;
2458	error:
2459	filemap_invalidate_unlock_shared(mapping);
2460	folio_put(folio);
2461	return error;
2462	}
2463
2464	static int filemap_readahead(struct kiocb *iocb, struct file *file,
2465	struct address_space *mapping, struct folio *folio,
2466	pgoff_t last_index)
2467	{
2468	DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, folio->index);
2469
2470	if (iocb->ki_flags & IOCB_NOIO)
2471	return -EAGAIN;
2472	page_cache_async_ra(&ractl, folio, req_count: last_index - folio->index);
2473	return 0;
2474	}
2475
2476	static int filemap_get_pages(struct kiocb *iocb, size_t count,
2477	struct folio_batch *fbatch, bool need_uptodate)
2478	{
2479	struct file *filp = iocb->ki_filp;
2480	struct address_space *mapping = filp->f_mapping;
2481	struct file_ra_state *ra = &filp->f_ra;
2482	pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
2483	pgoff_t last_index;
2484	struct folio *folio;
2485	int err = 0;
2486
2487	/* "last_index" is the index of the page beyond the end of the read */
2488	last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE);
2489	retry:
2490	if (fatal_signal_pending(current))
2491	return -EINTR;
2492
2493	filemap_get_read_batch(mapping, index, max: last_index - 1, fbatch);
2494	if (!folio_batch_count(fbatch)) {
2495	if (iocb->ki_flags & IOCB_NOIO)
2496	return -EAGAIN;
2497	page_cache_sync_readahead(mapping, ra, file: filp, index,
2498	req_count: last_index - index);
2499	filemap_get_read_batch(mapping, index, max: last_index - 1, fbatch);
2500	}
2501	if (!folio_batch_count(fbatch)) {
2502	if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
2503	return -EAGAIN;
2504	err = filemap_create_folio(file: filp, mapping,
2505	index: iocb->ki_pos >> PAGE_SHIFT, fbatch);
2506	if (err == AOP_TRUNCATED_PAGE)
2507	goto retry;
2508	return err;
2509	}
2510
2511	folio = fbatch->folios[folio_batch_count(fbatch) - 1];
2512	if (folio_test_readahead(folio)) {
2513	err = filemap_readahead(iocb, file: filp, mapping, folio, last_index);
2514	if (err)
2515	goto err;
2516	}
2517	if (!folio_test_uptodate(folio)) {
2518	if ((iocb->ki_flags & IOCB_WAITQ) &&
2519	folio_batch_count(fbatch) > 1)
2520	iocb->ki_flags |= IOCB_NOWAIT;
2521	err = filemap_update_page(iocb, mapping, count, folio,
2522	need_uptodate);
2523	if (err)
2524	goto err;
2525	}
2526
2527	return 0;
2528	err:
2529	if (err < 0)
2530	folio_put(folio);
2531	if (likely(--fbatch->nr))
2532	return 0;
2533	if (err == AOP_TRUNCATED_PAGE)
2534	goto retry;
2535	return err;
2536	}
2537
2538	static inline bool pos_same_folio(loff_t pos1, loff_t pos2, struct folio *folio)
2539	{
2540	unsigned int shift = folio_shift(folio);
2541
2542	return (pos1 >> shift == pos2 >> shift);
2543	}
2544
2545	/**
2546	* filemap_read - Read data from the page cache.
2547	* @iocb: The iocb to read.
2548	* @iter: Destination for the data.
2549	* @already_read: Number of bytes already read by the caller.
2550	*
2551	* Copies data from the page cache. If the data is not currently present,
2552	* uses the readahead and read_folio address_space operations to fetch it.
2553	*
2554	* Return: Total number of bytes copied, including those already read by
2555	* the caller. If an error happens before any bytes are copied, returns
2556	* a negative error number.
2557	*/
2558	ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
2559	ssize_t already_read)
2560	{
2561	struct file *filp = iocb->ki_filp;
2562	struct file_ra_state *ra = &filp->f_ra;
2563	struct address_space *mapping = filp->f_mapping;
2564	struct inode *inode = mapping->host;
2565	struct folio_batch fbatch;
2566	int i, error = 0;
2567	bool writably_mapped;
2568	loff_t isize, end_offset;
2569	loff_t last_pos = ra->prev_pos;
2570
2571	if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
2572	return 0;
2573	if (unlikely(!iov_iter_count(iter)))
2574	return 0;
2575
2576	iov_iter_truncate(i: iter, count: inode->i_sb->s_maxbytes);
2577	folio_batch_init(fbatch: &fbatch);
2578
2579	do {
2580	cond_resched();
2581
2582	/*
2583	* If we've already successfully copied some data, then we
2584	* can no longer safely return -EIOCBQUEUED. Hence mark
2585	* an async read NOWAIT at that point.
2586	*/
2587	if ((iocb->ki_flags & IOCB_WAITQ) && already_read)
2588	iocb->ki_flags |= IOCB_NOWAIT;
2589
2590	if (unlikely(iocb->ki_pos >= i_size_read(inode)))
2591	break;
2592
2593	error = filemap_get_pages(iocb, count: iter->count, fbatch: &fbatch, need_uptodate: false);
2594	if (error < 0)
2595	break;
2596
2597	/*
2598	* i_size must be checked after we know the pages are Uptodate.
2599	*
2600	* Checking i_size after the check allows us to calculate
2601	* the correct value for "nr", which means the zero-filled
2602	* part of the page is not copied back to userspace (unless
2603	* another truncate extends the file - this is desired though).
2604	*/
2605	isize = i_size_read(inode);
2606	if (unlikely(iocb->ki_pos >= isize))
2607	goto put_folios;
2608	end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);
2609
2610	/*
2611	* Once we start copying data, we don't want to be touching any
2612	* cachelines that might be contended:
2613	*/
2614	writably_mapped = mapping_writably_mapped(mapping);
2615
2616	/*
2617	* When a read accesses the same folio several times, only
2618	* mark it as accessed the first time.
2619	*/
2620	if (!pos_same_folio(pos1: iocb->ki_pos, pos2: last_pos - 1,
2621	folio: fbatch.folios[0]))
2622	folio_mark_accessed(fbatch.folios[0]);
2623
2624	for (i = 0; i < folio_batch_count(fbatch: &fbatch); i++) {
2625	struct folio *folio = fbatch.folios[i];
2626	size_t fsize = folio_size(folio);
2627	size_t offset = iocb->ki_pos & (fsize - 1);
2628	size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
2629	fsize - offset);
2630	size_t copied;
2631
2632	if (end_offset < folio_pos(folio))
2633	break;
2634	if (i > 0)
2635	folio_mark_accessed(folio);
2636	/*
2637	* If users can be writing to this folio using arbitrary
2638	* virtual addresses, take care of potential aliasing
2639	* before reading the folio on the kernel side.
2640	*/
2641	if (writably_mapped)
2642	flush_dcache_folio(folio);
2643
2644	copied = copy_folio_to_iter(folio, offset, bytes, i: iter);
2645
2646	already_read += copied;
2647	iocb->ki_pos += copied;
2648	last_pos = iocb->ki_pos;
2649
2650	if (copied < bytes) {
2651	error = -EFAULT;
2652	break;
2653	}
2654	}
2655	put_folios:
2656	for (i = 0; i < folio_batch_count(fbatch: &fbatch); i++)
2657	folio_put(folio: fbatch.folios[i]);
2658	folio_batch_init(fbatch: &fbatch);
2659	} while (iov_iter_count(i: iter) && iocb->ki_pos < isize && !error);
2660
2661	file_accessed(file: filp);
2662	ra->prev_pos = last_pos;
2663	return already_read ? already_read : error;
2664	}
2665	EXPORT_SYMBOL_GPL(filemap_read);
2666
2667	int kiocb_write_and_wait(struct kiocb *iocb, size_t count)
2668	{
2669	struct address_space *mapping = iocb->ki_filp->f_mapping;
2670	loff_t pos = iocb->ki_pos;
2671	loff_t end = pos + count - 1;
2672
2673	if (iocb->ki_flags & IOCB_NOWAIT) {
2674	if (filemap_range_needs_writeback(mapping, start_byte: pos, end_byte: end))
2675	return -EAGAIN;
2676	return 0;
2677	}
2678
2679	return filemap_write_and_wait_range(mapping, pos, end);
2680	}
2681
2682	int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
2683	{
2684	struct address_space *mapping = iocb->ki_filp->f_mapping;
2685	loff_t pos = iocb->ki_pos;
2686	loff_t end = pos + count - 1;
2687	int ret;
2688
2689	if (iocb->ki_flags & IOCB_NOWAIT) {
2690	/* we could block if there are any pages in the range */
2691	if (filemap_range_has_page(mapping, pos, end))
2692	return -EAGAIN;
2693	} else {
2694	ret = filemap_write_and_wait_range(mapping, pos, end);
2695	if (ret)
2696	return ret;
2697	}
2698
2699	/*
2700	* After a write we want buffered reads to be sure to go to disk to get
2701	* the new data. We invalidate clean cached page from the region we're
2702	* about to write. We do this *before* the write so that we can return
2703	* without clobbering -EIOCBQUEUED from ->direct_IO().
2704	*/
2705	return invalidate_inode_pages2_range(mapping, start: pos >> PAGE_SHIFT,
2706	end: end >> PAGE_SHIFT);
2707	}
2708
2709	/**
2710	* generic_file_read_iter - generic filesystem read routine
2711	* @iocb: kernel I/O control block
2712	* @iter: destination for the data read
2713	*
2714	* This is the "read_iter()" routine for all filesystems
2715	* that can use the page cache directly.
2716	*
2717	* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall
2718	* be returned when no data can be read without waiting for I/O requests
2719	* to complete; it doesn't prevent readahead.
2720	*
2721	* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O
2722	* requests shall be made for the read or for readahead. When no data
2723	* can be read, -EAGAIN shall be returned. When readahead would be
2724	* triggered, a partial, possibly empty read shall be returned.
2725	*
2726	* Return:
2727	* * number of bytes copied, even for partial reads
2728	* * negative error code (or 0 if IOCB_NOIO) if nothing was read
2729	*/
2730	ssize_t
2731	generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2732	{
2733	size_t count = iov_iter_count(i: iter);
2734	ssize_t retval = 0;
2735
2736	if (!count)
2737	return 0; /* skip atime */
2738
2739	if (iocb->ki_flags & IOCB_DIRECT) {
2740	struct file *file = iocb->ki_filp;
2741	struct address_space *mapping = file->f_mapping;
2742	struct inode *inode = mapping->host;
2743
2744	retval = kiocb_write_and_wait(iocb, count);
2745	if (retval < 0)
2746	return retval;
2747	file_accessed(file);
2748
2749	retval = mapping->a_ops->direct_IO(iocb, iter);
2750	if (retval >= 0) {
2751	iocb->ki_pos += retval;
2752	count -= retval;
2753	}
2754	if (retval != -EIOCBQUEUED)
2755	iov_iter_revert(i: iter, bytes: count - iov_iter_count(i: iter));
2756
2757	/*
2758	* Btrfs can have a short DIO read if we encounter
2759	* compressed extents, so if there was an error, or if
2760	* we've already read everything we wanted to, or if
2761	* there was a short read because we hit EOF, go ahead
2762	* and return. Otherwise fallthrough to buffered io for
2763	* the rest of the read. Buffered reads will not work for
2764	* DAX files, so don't bother trying.
2765	*/
2766	if (retval < 0 || !count || IS_DAX(inode))
2767	return retval;
2768	if (iocb->ki_pos >= i_size_read(inode))
2769	return retval;
2770	}
2771
2772	return filemap_read(iocb, iter, retval);
2773	}
2774	EXPORT_SYMBOL(generic_file_read_iter);
2775
2776	/*
2777	* Splice subpages from a folio into a pipe.
2778	*/
2779	size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
2780	struct folio *folio, loff_t fpos, size_t size)
2781	{
2782	struct page *page;
2783	size_t spliced = 0, offset = offset_in_folio(folio, fpos);
2784
2785	page = folio_page(folio, offset / PAGE_SIZE);
2786	size = min(size, folio_size(folio) - offset);
2787	offset %= PAGE_SIZE;
2788
2789	while (spliced < size &&
2790	!pipe_full(head: pipe->head, tail: pipe->tail, limit: pipe->max_usage)) {
2791	struct pipe_buffer *buf = pipe_head_buf(pipe);
2792	size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced);
2793
2794	*buf = (struct pipe_buffer) {
2795	.ops = &page_cache_pipe_buf_ops,
2796	.page = page,
2797	.offset = offset,
2798	.len = part,
2799	};
2800	folio_get(folio);
2801	pipe->head++;
2802	page++;
2803	spliced += part;
2804	offset = 0;
2805	}
2806
2807	return spliced;
2808	}
2809
2810	/**
2811	* filemap_splice_read - Splice data from a file's pagecache into a pipe
2812	* @in: The file to read from
2813	* @ppos: Pointer to the file position to read from
2814	* @pipe: The pipe to splice into
2815	* @len: The amount to splice
2816	* @flags: The SPLICE_F_* flags
2817	*
2818	* This function gets folios from a file's pagecache and splices them into the
2819	* pipe. Readahead will be called as necessary to fill more folios. This may
2820	* be used for blockdevs also.
2821	*
2822	* Return: On success, the number of bytes read will be returned and *@ppos
2823	* will be updated if appropriate; 0 will be returned if there is no more data
2824	* to be read; -EAGAIN will be returned if the pipe had no space, and some
2825	* other negative error code will be returned on error. A short read may occur
2826	* if the pipe has insufficient space, we reach the end of the data or we hit a
2827	* hole.
2828	*/
2829	ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
2830	struct pipe_inode_info *pipe,
2831	size_t len, unsigned int flags)
2832	{
2833	struct folio_batch fbatch;
2834	struct kiocb iocb;
2835	size_t total_spliced = 0, used, npages;
2836	loff_t isize, end_offset;
2837	bool writably_mapped;
2838	int i, error = 0;
2839
2840	if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes))
2841	return 0;
2842
2843	init_sync_kiocb(kiocb: &iocb, filp: in);
2844	iocb.ki_pos = *ppos;
2845
2846	/* Work out how much data we can actually add into the pipe */
2847	used = pipe_occupancy(head: pipe->head, tail: pipe->tail);
2848	npages = max_t(ssize_t, pipe->max_usage - used, 0);
2849	len = min_t(size_t, len, npages * PAGE_SIZE);
2850
2851	folio_batch_init(fbatch: &fbatch);
2852
2853	do {
2854	cond_resched();
2855
2856	if (*ppos >= i_size_read(inode: in->f_mapping->host))
2857	break;
2858
2859	iocb.ki_pos = *ppos;
2860	error = filemap_get_pages(iocb: &iocb, count: len, fbatch: &fbatch, need_uptodate: true);
2861	if (error < 0)
2862	break;
2863
2864	/*
2865	* i_size must be checked after we know the pages are Uptodate.
2866	*
2867	* Checking i_size after the check allows us to calculate
2868	* the correct value for "nr", which means the zero-filled
2869	* part of the page is not copied back to userspace (unless
2870	* another truncate extends the file - this is desired though).
2871	*/
2872	isize = i_size_read(inode: in->f_mapping->host);
2873	if (unlikely(*ppos >= isize))
2874	break;
2875	end_offset = min_t(loff_t, isize, *ppos + len);
2876
2877	/*
2878	* Once we start copying data, we don't want to be touching any
2879	* cachelines that might be contended:
2880	*/
2881	writably_mapped = mapping_writably_mapped(mapping: in->f_mapping);
2882
2883	for (i = 0; i < folio_batch_count(fbatch: &fbatch); i++) {
2884	struct folio *folio = fbatch.folios[i];
2885	size_t n;
2886
2887	if (folio_pos(folio) >= end_offset)
2888	goto out;
2889	folio_mark_accessed(folio);
2890
2891	/*
2892	* If users can be writing to this folio using arbitrary
2893	* virtual addresses, take care of potential aliasing
2894	* before reading the folio on the kernel side.
2895	*/
2896	if (writably_mapped)
2897	flush_dcache_folio(folio);
2898
2899	n = min_t(loff_t, len, isize - *ppos);
2900	n = splice_folio_into_pipe(pipe, folio, fpos: *ppos, size: n);
2901	if (!n)
2902	goto out;
2903	len -= n;
2904	total_spliced += n;
2905	*ppos += n;
2906	in->f_ra.prev_pos = *ppos;
2907	if (pipe_full(head: pipe->head, tail: pipe->tail, limit: pipe->max_usage))
2908	goto out;
2909	}
2910
2911	folio_batch_release(fbatch: &fbatch);
2912	} while (len);
2913
2914	out:
2915	folio_batch_release(fbatch: &fbatch);
2916	file_accessed(file: in);
2917
2918	return total_spliced ? total_spliced : error;
2919	}
2920	EXPORT_SYMBOL(filemap_splice_read);
2921
2922	static inline loff_t folio_seek_hole_data(struct xa_state *xas,
2923	struct address_space *mapping, struct folio *folio,
2924	loff_t start, loff_t end, bool seek_data)
2925	{
2926	const struct address_space_operations *ops = mapping->a_ops;
2927	size_t offset, bsz = i_blocksize(node: mapping->host);
2928
2929	if (xa_is_value(entry: folio) || folio_test_uptodate(folio))
2930	return seek_data ? start : end;
2931	if (!ops->is_partially_uptodate)
2932	return seek_data ? end : start;
2933
2934	xas_pause(xas);
2935	rcu_read_unlock();
2936	folio_lock(folio);
2937	if (unlikely(folio->mapping != mapping))
2938	goto unlock;
2939
2940	offset = offset_in_folio(folio, start) & ~(bsz - 1);
2941
2942	do {
2943	if (ops->is_partially_uptodate(folio, offset, bsz) ==
2944	seek_data)
2945	break;
2946	start = (start + bsz) & ~(bsz - 1);
2947	offset += bsz;
2948	} while (offset < folio_size(folio));
2949	unlock:
2950	folio_unlock(folio);
2951	rcu_read_lock();
2952	return start;
2953	}
2954
2955	static inline size_t seek_folio_size(struct xa_state *xas, struct folio *folio)
2956	{
2957	if (xa_is_value(entry: folio))
2958	return PAGE_SIZE << xa_get_order(xas->xa, index: xas->xa_index);
2959	return folio_size(folio);
2960	}
2961
2962	/**
2963	* mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache.
2964	* @mapping: Address space to search.
2965	* @start: First byte to consider.
2966	* @end: Limit of search (exclusive).
2967	* @whence: Either SEEK_HOLE or SEEK_DATA.
2968	*
2969	* If the page cache knows which blocks contain holes and which blocks
2970	* contain data, your filesystem can use this function to implement
2971	* SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are
2972	* entirely memory-based such as tmpfs, and filesystems which support
2973	* unwritten extents.
2974	*
2975	* Return: The requested offset on success, or -ENXIO if @whence specifies
2976	* SEEK_DATA and there is no data after @start. There is an implicit hole
2977	* after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start
2978	* and @end contain data.
2979	*/
2980	loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
2981	loff_t end, int whence)
2982	{
2983	XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT);
2984	pgoff_t max = (end - 1) >> PAGE_SHIFT;
2985	bool seek_data = (whence == SEEK_DATA);
2986	struct folio *folio;
2987
2988	if (end <= start)
2989	return -ENXIO;
2990
2991	rcu_read_lock();
2992	while ((folio = find_get_entry(xas: &xas, max, XA_PRESENT))) {
2993	loff_t pos = (u64)xas.xa_index << PAGE_SHIFT;
2994	size_t seek_size;
2995
2996	if (start < pos) {
2997	if (!seek_data)
2998	goto unlock;
2999	start = pos;
3000	}
3001
3002	seek_size = seek_folio_size(xas: &xas, folio);
3003	pos = round_up((u64)pos + 1, seek_size);
3004	start = folio_seek_hole_data(xas: &xas, mapping, folio, start, end: pos,
3005	seek_data);
3006	if (start < pos)
3007	goto unlock;
3008	if (start >= end)
3009	break;
3010	if (seek_size > PAGE_SIZE)
3011	xas_set(xas: &xas, index: pos >> PAGE_SHIFT);
3012	if (!xa_is_value(entry: folio))
3013	folio_put(folio);
3014	}
3015	if (seek_data)
3016	start = -ENXIO;
3017	unlock:
3018	rcu_read_unlock();
3019	if (folio && !xa_is_value(entry: folio))
3020	folio_put(folio);
3021	if (start > end)
3022	return end;
3023	return start;
3024	}
3025
3026	#ifdef CONFIG_MMU
3027	#define MMAP_LOTSAMISS (100)
3028	/*
3029	* lock_folio_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
3030	* @vmf - the vm_fault for this fault.
3031	* @folio - the folio to lock.
3032	* @fpin - the pointer to the file we may pin (or is already pinned).
3033	*
3034	* This works similar to lock_folio_or_retry in that it can drop the
3035	* mmap_lock. It differs in that it actually returns the folio locked
3036	* if it returns 1 and 0 if it couldn't lock the folio. If we did have
3037	* to drop the mmap_lock then fpin will point to the pinned file and
3038	* needs to be fput()'ed at a later point.
3039	*/
3040	static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio,
3041	struct file **fpin)
3042	{
3043	if (folio_trylock(folio))
3044	return 1;
3045
3046	/*
3047	* NOTE! This will make us return with VM_FAULT_RETRY, but with
3048	* the fault lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
3049	* is supposed to work. We have way too many special cases..
3050	*/
3051	if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
3052	return 0;
3053
3054	*fpin = maybe_unlock_mmap_for_io(vmf, fpin: *fpin);
3055	if (vmf->flags & FAULT_FLAG_KILLABLE) {
3056	if (__folio_lock_killable(folio)) {
3057	/*
3058	* We didn't have the right flags to drop the
3059	* fault lock, but all fault_handlers only check
3060	* for fatal signals if we return VM_FAULT_RETRY,
3061	* so we need to drop the fault lock here and
3062	* return 0 if we don't have a fpin.
3063	*/
3064	if (*fpin == NULL)
3065	release_fault_lock(vmf);
3066	return 0;
3067	}
3068	} else
3069	__folio_lock(folio);
3070
3071	return 1;
3072	}
3073
3074	/*
3075	* Synchronous readahead happens when we don't even find a page in the page
3076	* cache at all. We don't want to perform IO under the mmap sem, so if we have
3077	* to drop the mmap sem we return the file that was pinned in order for us to do
3078	* that. If we didn't pin a file then we return NULL. The file that is
3079	* returned needs to be fput()'ed when we're done with it.
3080	*/
3081	static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
3082	{
3083	struct file *file = vmf->vma->vm_file;
3084	struct file_ra_state *ra = &file->f_ra;
3085	struct address_space *mapping = file->f_mapping;
3086	DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
3087	struct file *fpin = NULL;
3088	unsigned long vm_flags = vmf->vma->vm_flags;
3089	unsigned int mmap_miss;
3090
3091	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
3092	/* Use the readahead code, even if readahead is disabled */
3093	if (vm_flags & VM_HUGEPAGE) {
3094	fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3095	ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1);
3096	ra->size = HPAGE_PMD_NR;
3097	/*
3098	* Fetch two PMD folios, so we get the chance to actually
3099	* readahead, unless we've been told not to.
3100	*/
3101	if (!(vm_flags & VM_RAND_READ))
3102	ra->size *= 2;
3103	ra->async_size = HPAGE_PMD_NR;
3104	page_cache_ra_order(&ractl, ra, HPAGE_PMD_ORDER);
3105	return fpin;
3106	}
3107	#endif
3108
3109	/* If we don't want any read-ahead, don't bother */
3110	if (vm_flags & VM_RAND_READ)
3111	return fpin;
3112	if (!ra->ra_pages)
3113	return fpin;
3114
3115	if (vm_flags & VM_SEQ_READ) {
3116	fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3117	page_cache_sync_ra(&ractl, req_count: ra->ra_pages);
3118	return fpin;
3119	}
3120
3121	/* Avoid banging the cache line if not needed */
3122	mmap_miss = READ_ONCE(ra->mmap_miss);
3123	if (mmap_miss < MMAP_LOTSAMISS * 10)
3124	WRITE_ONCE(ra->mmap_miss, ++mmap_miss);
3125
3126	/*
3127	* Do we miss much more than hit in this file? If so,
3128	* stop bothering with read-ahead. It will only hurt.
3129	*/
3130	if (mmap_miss > MMAP_LOTSAMISS)
3131	return fpin;
3132
3133	/*
3134	* mmap read-around
3135	*/
3136	fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3137	ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
3138	ra->size = ra->ra_pages;
3139	ra->async_size = ra->ra_pages / 4;
3140	ractl._index = ra->start;
3141	page_cache_ra_order(&ractl, ra, order: 0);
3142	return fpin;
3143	}
3144
3145	/*
3146	* Asynchronous readahead happens when we find the page and PG_readahead,
3147	* so we want to possibly extend the readahead further. We return the file that
3148	* was pinned if we have to drop the mmap_lock in order to do IO.
3149	*/
3150	static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
3151	struct folio *folio)
3152	{
3153	struct file *file = vmf->vma->vm_file;
3154	struct file_ra_state *ra = &file->f_ra;
3155	DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff);
3156	struct file *fpin = NULL;
3157	unsigned int mmap_miss;
3158
3159	/* If we don't want any read-ahead, don't bother */
3160	if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
3161	return fpin;
3162
3163	mmap_miss = READ_ONCE(ra->mmap_miss);
3164	if (mmap_miss)
3165	WRITE_ONCE(ra->mmap_miss, --mmap_miss);
3166
3167	if (folio_test_readahead(folio)) {
3168	fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3169	page_cache_async_ra(&ractl, folio, req_count: ra->ra_pages);
3170	}
3171	return fpin;
3172	}
3173
3174	/**
3175	* filemap_fault - read in file data for page fault handling
3176	* @vmf: struct vm_fault containing details of the fault
3177	*
3178	* filemap_fault() is invoked via the vma operations vector for a
3179	* mapped memory region to read in file data during a page fault.
3180	*
3181	* The goto's are kind of ugly, but this streamlines the normal case of having
3182	* it in the page cache, and handles the special cases reasonably without
3183	* having a lot of duplicated code.
3184	*
3185	* vma->vm_mm->mmap_lock must be held on entry.
3186	*
3187	* If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
3188	* may be dropped before doing I/O or by lock_folio_maybe_drop_mmap().
3189	*
3190	* If our return value does not have VM_FAULT_RETRY set, the mmap_lock
3191	* has not been released.
3192	*
3193	* We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
3194	*
3195	* Return: bitwise-OR of %VM_FAULT_ codes.
3196	*/
3197	vm_fault_t filemap_fault(struct vm_fault *vmf)
3198	{
3199	int error;
3200	struct file *file = vmf->vma->vm_file;
3201	struct file *fpin = NULL;
3202	struct address_space *mapping = file->f_mapping;
3203	struct inode *inode = mapping->host;
3204	pgoff_t max_idx, index = vmf->pgoff;
3205	struct folio *folio;
3206	vm_fault_t ret = 0;
3207	bool mapping_locked = false;
3208
3209	max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
3210	if (unlikely(index >= max_idx))
3211	return VM_FAULT_SIGBUS;
3212
3213	/*
3214	* Do we have something in the page cache already?
3215	*/
3216	folio = filemap_get_folio(mapping, index);
3217	if (likely(!IS_ERR(folio))) {
3218	/*
3219	* We found the page, so try async readahead before waiting for
3220	* the lock.
3221	*/
3222	if (!(vmf->flags & FAULT_FLAG_TRIED))
3223	fpin = do_async_mmap_readahead(vmf, folio);
3224	if (unlikely(!folio_test_uptodate(folio))) {
3225	filemap_invalidate_lock_shared(mapping);
3226	mapping_locked = true;
3227	}
3228	} else {
3229	/* No page in the page cache at all */
3230	count_vm_event(item: PGMAJFAULT);
3231	count_memcg_event_mm(mm: vmf->vma->vm_mm, idx: PGMAJFAULT);
3232	ret = VM_FAULT_MAJOR;
3233	fpin = do_sync_mmap_readahead(vmf);
3234	retry_find:
3235	/*
3236	* See comment in filemap_create_folio() why we need
3237	* invalidate_lock
3238	*/
3239	if (!mapping_locked) {
3240	filemap_invalidate_lock_shared(mapping);
3241	mapping_locked = true;
3242	}
3243	folio = __filemap_get_folio(mapping, index,
3244	FGP_CREAT|FGP_FOR_MMAP,
3245	vmf->gfp_mask);
3246	if (IS_ERR(ptr: folio)) {
3247	if (fpin)
3248	goto out_retry;
3249	filemap_invalidate_unlock_shared(mapping);
3250	return VM_FAULT_OOM;
3251	}
3252	}
3253
3254	if (!lock_folio_maybe_drop_mmap(vmf, folio, fpin: &fpin))
3255	goto out_retry;
3256
3257	/* Did it get truncated? */
3258	if (unlikely(folio->mapping != mapping)) {
3259	folio_unlock(folio);
3260	folio_put(folio);
3261	goto retry_find;
3262	}
3263	VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
3264
3265	/*
3266	* We have a locked folio in the page cache, now we need to check
3267	* that it's up-to-date. If not, it is going to be due to an error,
3268	* or because readahead was otherwise unable to retrieve it.
3269	*/
3270	if (unlikely(!folio_test_uptodate(folio))) {
3271	/*
3272	* If the invalidate lock is not held, the folio was in cache
3273	* and uptodate and now it is not. Strange but possible since we
3274	* didn't hold the page lock all the time. Let's drop
3275	* everything, get the invalidate lock and try again.
3276	*/
3277	if (!mapping_locked) {
3278	folio_unlock(folio);
3279	folio_put(folio);
3280	goto retry_find;
3281	}
3282
3283	/*
3284	* OK, the folio is really not uptodate. This can be because the
3285	* VMA has the VM_RAND_READ flag set, or because an error
3286	* arose. Let's read it in directly.
3287	*/
3288	goto page_not_uptodate;
3289	}
3290
3291	/*
3292	* We've made it this far and we had to drop our mmap_lock, now is the
3293	* time to return to the upper layer and have it re-find the vma and
3294	* redo the fault.
3295	*/
3296	if (fpin) {
3297	folio_unlock(folio);
3298	goto out_retry;
3299	}
3300	if (mapping_locked)
3301	filemap_invalidate_unlock_shared(mapping);
3302
3303	/*
3304	* Found the page and have a reference on it.
3305	* We must recheck i_size under page lock.
3306	*/
3307	max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
3308	if (unlikely(index >= max_idx)) {
3309	folio_unlock(folio);
3310	folio_put(folio);
3311	return VM_FAULT_SIGBUS;
3312	}
3313
3314	vmf->page = folio_file_page(folio, index);
3315	return ret | VM_FAULT_LOCKED;
3316
3317	page_not_uptodate:
3318	/*
3319	* Umm, take care of errors if the page isn't up-to-date.
3320	* Try to re-read it _once_. We do this synchronously,
3321	* because there really aren't any performance issues here
3322	* and we need to check for errors.
3323	*/
3324	fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3325	error = filemap_read_folio(file, filler: mapping->a_ops->read_folio, folio);
3326	if (fpin)
3327	goto out_retry;
3328	folio_put(folio);
3329
3330	if (!error || error == AOP_TRUNCATED_PAGE)
3331	goto retry_find;
3332	filemap_invalidate_unlock_shared(mapping);
3333
3334	return VM_FAULT_SIGBUS;
3335
3336	out_retry:
3337	/*
3338	* We dropped the mmap_lock, we need to return to the fault handler to
3339	* re-find the vma and come back and find our hopefully still populated
3340	* page.
3341	*/
3342	if (!IS_ERR(ptr: folio))
3343	folio_put(folio);
3344	if (mapping_locked)
3345	filemap_invalidate_unlock_shared(mapping);
3346	if (fpin)
3347	fput(fpin);
3348	return ret | VM_FAULT_RETRY;
3349	}
3350	EXPORT_SYMBOL(filemap_fault);
3351
3352	static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio,
3353	pgoff_t start)
3354	{
3355	struct mm_struct *mm = vmf->vma->vm_mm;
3356
3357	/* Huge page is mapped? No need to proceed. */
3358	if (pmd_trans_huge(pmd: *vmf->pmd)) {
3359	folio_unlock(folio);
3360	folio_put(folio);
3361	return true;
3362	}
3363
3364	if (pmd_none(pmd: *vmf->pmd) && folio_test_pmd_mappable(folio)) {
3365	struct page *page = folio_file_page(folio, index: start);
3366	vm_fault_t ret = do_set_pmd(vmf, page);
3367	if (!ret) {
3368	/* The page is mapped successfully, reference consumed. */
3369	folio_unlock(folio);
3370	return true;
3371	}
3372	}
3373
3374	if (pmd_none(pmd: *vmf->pmd))
3375	pmd_install(mm, pmd: vmf->pmd, pte: &vmf->prealloc_pte);
3376
3377	return false;
3378	}
3379
3380	static struct folio *next_uptodate_folio(struct xa_state *xas,
3381	struct address_space *mapping, pgoff_t end_pgoff)
3382	{
3383	struct folio *folio = xas_next_entry(xas, max: end_pgoff);
3384	unsigned long max_idx;
3385
3386	do {
3387	if (!folio)
3388	return NULL;
3389	if (xas_retry(xas, entry: folio))
3390	continue;
3391	if (xa_is_value(entry: folio))
3392	continue;
3393	if (folio_test_locked(folio))
3394	continue;
3395	if (!folio_try_get_rcu(folio))
3396	continue;
3397	/* Has the page moved or been split? */
3398	if (unlikely(folio != xas_reload(xas)))
3399	goto skip;
3400	if (!folio_test_uptodate(folio) || folio_test_readahead(folio))
3401	goto skip;
3402	if (!folio_trylock(folio))
3403	goto skip;
3404	if (folio->mapping != mapping)
3405	goto unlock;
3406	if (!folio_test_uptodate(folio))
3407	goto unlock;
3408	max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
3409	if (xas->xa_index >= max_idx)
3410	goto unlock;
3411	return folio;
3412	unlock:
3413	folio_unlock(folio);
3414	skip:
3415	folio_put(folio);
3416	} while ((folio = xas_next_entry(xas, max: end_pgoff)) != NULL);
3417
3418	return NULL;
3419	}
3420
3421	/*
3422	* Map page range [start_page, start_page + nr_pages) of folio.
3423	* start_page is gotten from start by folio_page(folio, start)
3424	*/
3425	static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
3426	struct folio *folio, unsigned long start,
3427	unsigned long addr, unsigned int nr_pages,
3428	unsigned int *mmap_miss)
3429	{
3430	vm_fault_t ret = 0;
3431	struct page *page = folio_page(folio, start);
3432	unsigned int count = 0;
3433	pte_t *old_ptep = vmf->pte;
3434
3435	do {
3436	if (PageHWPoison(page: page + count))
3437	goto skip;
3438
3439	(*mmap_miss)++;
3440
3441	/*
3442	* NOTE: If there're PTE markers, we'll leave them to be
3443	* handled in the specific fault path, and it'll prohibit the
3444	* fault-around logic.
3445	*/
3446	if (!pte_none(pte: vmf->pte[count]))
3447	goto skip;
3448
3449	count++;
3450	continue;
3451	skip:
3452	if (count) {
3453	set_pte_range(vmf, folio, page, nr: count, addr);
3454	folio_ref_add(folio, nr: count);
3455	if (in_range(vmf->address, addr, count * PAGE_SIZE))
3456	ret = VM_FAULT_NOPAGE;
3457	}
3458
3459	count++;
3460	page += count;
3461	vmf->pte += count;
3462	addr += count * PAGE_SIZE;
3463	count = 0;
3464	} while (--nr_pages > 0);
3465
3466	if (count) {
3467	set_pte_range(vmf, folio, page, nr: count, addr);
3468	folio_ref_add(folio, nr: count);
3469	if (in_range(vmf->address, addr, count * PAGE_SIZE))
3470	ret = VM_FAULT_NOPAGE;
3471	}
3472
3473	vmf->pte = old_ptep;
3474
3475	return ret;
3476	}
3477
3478	static vm_fault_t filemap_map_order0_folio(struct vm_fault *vmf,
3479	struct folio *folio, unsigned long addr,
3480	unsigned int *mmap_miss)
3481	{
3482	vm_fault_t ret = 0;
3483	struct page *page = &folio->page;
3484
3485	if (PageHWPoison(page))
3486	return ret;
3487
3488	(*mmap_miss)++;
3489
3490	/*
3491	* NOTE: If there're PTE markers, we'll leave them to be
3492	* handled in the specific fault path, and it'll prohibit
3493	* the fault-around logic.
3494	*/
3495	if (!pte_none(pte: ptep_get(ptep: vmf->pte)))
3496	return ret;
3497
3498	if (vmf->address == addr)
3499	ret = VM_FAULT_NOPAGE;
3500
3501	set_pte_range(vmf, folio, page, nr: 1, addr);
3502	folio_ref_inc(folio);
3503
3504	return ret;
3505	}
3506
3507	vm_fault_t filemap_map_pages(struct vm_fault *vmf,
3508	pgoff_t start_pgoff, pgoff_t end_pgoff)
3509	{
3510	struct vm_area_struct *vma = vmf->vma;
3511	struct file *file = vma->vm_file;
3512	struct address_space *mapping = file->f_mapping;
3513	pgoff_t last_pgoff = start_pgoff;
3514	unsigned long addr;
3515	XA_STATE(xas, &mapping->i_pages, start_pgoff);
3516	struct folio *folio;
3517	vm_fault_t ret = 0;
3518	unsigned int nr_pages = 0, mmap_miss = 0, mmap_miss_saved;
3519
3520	rcu_read_lock();
3521	folio = next_uptodate_folio(xas: &xas, mapping, end_pgoff);
3522	if (!folio)
3523	goto out;
3524
3525	if (filemap_map_pmd(vmf, folio, start: start_pgoff)) {
3526	ret = VM_FAULT_NOPAGE;
3527	goto out;
3528	}
3529
3530	addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
3531	vmf->pte = pte_offset_map_lock(mm: vma->vm_mm, pmd: vmf->pmd, addr, ptlp: &vmf->ptl);
3532	if (!vmf->pte) {
3533	folio_unlock(folio);
3534	folio_put(folio);
3535	goto out;
3536	}
3537	do {
3538	unsigned long end;
3539
3540	addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
3541	vmf->pte += xas.xa_index - last_pgoff;
3542	last_pgoff = xas.xa_index;
3543	end = folio_next_index(folio) - 1;
3544	nr_pages = min(end, end_pgoff) - xas.xa_index + 1;
3545
3546	if (!folio_test_large(folio))
3547	ret |= filemap_map_order0_folio(vmf,
3548	folio, addr, mmap_miss: &mmap_miss);
3549	else
3550	ret |= filemap_map_folio_range(vmf, folio,
3551	start: xas.xa_index - folio->index, addr,
3552	nr_pages, mmap_miss: &mmap_miss);
3553
3554	folio_unlock(folio);
3555	folio_put(folio);
3556	} while ((folio = next_uptodate_folio(xas: &xas, mapping, end_pgoff)) != NULL);
3557	pte_unmap_unlock(vmf->pte, vmf->ptl);
3558	out:
3559	rcu_read_unlock();
3560
3561	mmap_miss_saved = READ_ONCE(file->f_ra.mmap_miss);
3562	if (mmap_miss >= mmap_miss_saved)
3563	WRITE_ONCE(file->f_ra.mmap_miss, 0);
3564	else
3565	WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss_saved - mmap_miss);
3566
3567	return ret;
3568	}
3569	EXPORT_SYMBOL(filemap_map_pages);
3570
3571	vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3572	{
3573	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
3574	struct folio *folio = page_folio(vmf->page);
3575	vm_fault_t ret = VM_FAULT_LOCKED;
3576
3577	sb_start_pagefault(sb: mapping->host->i_sb);
3578	file_update_time(file: vmf->vma->vm_file);
3579	folio_lock(folio);
3580	if (folio->mapping != mapping) {
3581	folio_unlock(folio);
3582	ret = VM_FAULT_NOPAGE;
3583	goto out;
3584	}
3585	/*
3586	* We mark the folio dirty already here so that when freeze is in
3587	* progress, we are guaranteed that writeback during freezing will
3588	* see the dirty folio and writeprotect it again.
3589	*/
3590	folio_mark_dirty(folio);
3591	folio_wait_stable(folio);
3592	out:
3593	sb_end_pagefault(sb: mapping->host->i_sb);
3594	return ret;
3595	}
3596
3597	const struct vm_operations_struct generic_file_vm_ops = {
3598	.fault = filemap_fault,
3599	.map_pages = filemap_map_pages,
3600	.page_mkwrite = filemap_page_mkwrite,
3601	};
3602
3603	/* This is used for a general mmap of a disk file */
3604
3605	int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
3606	{
3607	struct address_space *mapping = file->f_mapping;
3608
3609	if (!mapping->a_ops->read_folio)
3610	return -ENOEXEC;
3611	file_accessed(file);
3612	vma->vm_ops = &generic_file_vm_ops;
3613	return 0;
3614	}
3615
3616	/*
3617	* This is for filesystems which do not implement ->writepage.
3618	*/
3619	int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
3620	{
3621	if (vma_is_shared_maywrite(vma))
3622	return -EINVAL;
3623	return generic_file_mmap(file, vma);
3624	}
3625	#else
3626	vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3627	{
3628	return VM_FAULT_SIGBUS;
3629	}
3630	int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
3631	{
3632	return -ENOSYS;
3633	}
3634	int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
3635	{
3636	return -ENOSYS;
3637	}
3638	#endif /* CONFIG_MMU */
3639
3640	EXPORT_SYMBOL(filemap_page_mkwrite);
3641	EXPORT_SYMBOL(generic_file_mmap);
3642	EXPORT_SYMBOL(generic_file_readonly_mmap);
3643
3644	static struct folio *do_read_cache_folio(struct address_space *mapping,
3645	pgoff_t index, filler_t filler, struct file *file, gfp_t gfp)
3646	{
3647	struct folio *folio;
3648	int err;
3649
3650	if (!filler)
3651	filler = mapping->a_ops->read_folio;
3652	repeat:
3653	folio = filemap_get_folio(mapping, index);
3654	if (IS_ERR(ptr: folio)) {
3655	folio = filemap_alloc_folio(gfp, 0);
3656	if (!folio)
3657	return ERR_PTR(error: -ENOMEM);
3658	err = filemap_add_folio(mapping, folio, index, gfp);
3659	if (unlikely(err)) {
3660	folio_put(folio);
3661	if (err == -EEXIST)
3662	goto repeat;
3663	/* Presumably ENOMEM for xarray node */
3664	return ERR_PTR(error: err);
3665	}
3666
3667	goto filler;
3668	}
3669	if (folio_test_uptodate(folio))
3670	goto out;
3671
3672	if (!folio_trylock(folio)) {
3673	folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE);
3674	goto repeat;
3675	}
3676
3677	/* Folio was truncated from mapping */
3678	if (!folio->mapping) {
3679	folio_unlock(folio);
3680	folio_put(folio);
3681	goto repeat;
3682	}
3683
3684	/* Someone else locked and filled the page in a very small window */
3685	if (folio_test_uptodate(folio)) {
3686	folio_unlock(folio);
3687	goto out;
3688	}
3689
3690	filler:
3691	err = filemap_read_folio(file, filler, folio);
3692	if (err) {
3693	folio_put(folio);
3694	if (err == AOP_TRUNCATED_PAGE)
3695	goto repeat;
3696	return ERR_PTR(error: err);
3697	}
3698
3699	out:
3700	folio_mark_accessed(folio);
3701	return folio;
3702	}
3703
3704	/**
3705	* read_cache_folio - Read into page cache, fill it if needed.
3706	* @mapping: The address_space to read from.
3707	* @index: The index to read.
3708	* @filler: Function to perform the read, or NULL to use aops->read_folio().
3709	* @file: Passed to filler function, may be NULL if not required.
3710	*
3711	* Read one page into the page cache. If it succeeds, the folio returned
3712	* will contain @index, but it may not be the first page of the folio.
3713	*
3714	* If the filler function returns an error, it will be returned to the
3715	* caller.
3716	*
3717	* Context: May sleep. Expects mapping->invalidate_lock to be held.
3718	* Return: An uptodate folio on success, ERR_PTR() on failure.
3719	*/
3720	struct folio *read_cache_folio(struct address_space *mapping, pgoff_t index,
3721	filler_t filler, struct file *file)
3722	{
3723	return do_read_cache_folio(mapping, index, filler, file,
3724	gfp: mapping_gfp_mask(mapping));
3725	}
3726	EXPORT_SYMBOL(read_cache_folio);
3727
3728	/**
3729	* mapping_read_folio_gfp - Read into page cache, using specified allocation flags.
3730	* @mapping: The address_space for the folio.
3731	* @index: The index that the allocated folio will contain.
3732	* @gfp: The page allocator flags to use if allocating.
3733	*
3734	* This is the same as "read_cache_folio(mapping, index, NULL, NULL)", but with
3735	* any new memory allocations done using the specified allocation flags.
3736	*
3737	* The most likely error from this function is EIO, but ENOMEM is
3738	* possible and so is EINTR. If ->read_folio returns another error,
3739	* that will be returned to the caller.
3740	*
3741	* The function expects mapping->invalidate_lock to be already held.
3742	*
3743	* Return: Uptodate folio on success, ERR_PTR() on failure.
3744	*/
3745	struct folio *mapping_read_folio_gfp(struct address_space *mapping,
3746	pgoff_t index, gfp_t gfp)
3747	{
3748	return do_read_cache_folio(mapping, index, NULL, NULL, gfp);
3749	}
3750	EXPORT_SYMBOL(mapping_read_folio_gfp);
3751
3752	static struct page *do_read_cache_page(struct address_space *mapping,
3753	pgoff_t index, filler_t *filler, struct file *file, gfp_t gfp)
3754	{
3755	struct folio *folio;
3756
3757	folio = do_read_cache_folio(mapping, index, filler, file, gfp);
3758	if (IS_ERR(ptr: folio))
3759	return &folio->page;
3760	return folio_file_page(folio, index);
3761	}
3762
3763	struct page *read_cache_page(struct address_space *mapping,
3764	pgoff_t index, filler_t *filler, struct file *file)
3765	{
3766	return do_read_cache_page(mapping, index, filler, file,
3767	gfp: mapping_gfp_mask(mapping));
3768	}
3769	EXPORT_SYMBOL(read_cache_page);
3770
3771	/**
3772	* read_cache_page_gfp - read into page cache, using specified page allocation flags.
3773	* @mapping: the page's address_space
3774	* @index: the page index
3775	* @gfp: the page allocator flags to use if allocating
3776	*
3777	* This is the same as "read_mapping_page(mapping, index, NULL)", but with
3778	* any new page allocations done using the specified allocation flags.
3779	*
3780	* If the page does not get brought uptodate, return -EIO.
3781	*
3782	* The function expects mapping->invalidate_lock to be already held.
3783	*
3784	* Return: up to date page on success, ERR_PTR() on failure.
3785	*/
3786	struct page *read_cache_page_gfp(struct address_space *mapping,
3787	pgoff_t index,
3788	gfp_t gfp)
3789	{
3790	return do_read_cache_page(mapping, index, NULL, NULL, gfp);
3791	}
3792	EXPORT_SYMBOL(read_cache_page_gfp);
3793
3794	/*
3795	* Warn about a page cache invalidation failure during a direct I/O write.
3796	*/
3797	static void dio_warn_stale_pagecache(struct file *filp)
3798	{
3799	static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
3800	char pathname[128];
3801	char *path;
3802
3803	errseq_set(eseq: &filp->f_mapping->wb_err, err: -EIO);
3804	if (__ratelimit(&_rs)) {
3805	path = file_path(filp, pathname, sizeof(pathname));
3806	if (IS_ERR(ptr: path))
3807	path = "(unknown)";
3808	pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n");
3809	pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
3810	current->comm);
3811	}
3812	}
3813
3814	void kiocb_invalidate_post_direct_write(struct kiocb *iocb, size_t count)
3815	{
3816	struct address_space *mapping = iocb->ki_filp->f_mapping;
3817
3818	if (mapping->nrpages &&
3819	invalidate_inode_pages2_range(mapping,
3820	start: iocb->ki_pos >> PAGE_SHIFT,
3821	end: (iocb->ki_pos + count - 1) >> PAGE_SHIFT))
3822	dio_warn_stale_pagecache(filp: iocb->ki_filp);
3823	}
3824
3825	ssize_t
3826	generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
3827	{
3828	struct address_space *mapping = iocb->ki_filp->f_mapping;
3829	size_t write_len = iov_iter_count(i: from);
3830	ssize_t written;
3831
3832	/*
3833	* If a page can not be invalidated, return 0 to fall back
3834	* to buffered write.
3835	*/
3836	written = kiocb_invalidate_pages(iocb, count: write_len);
3837	if (written) {
3838	if (written == -EBUSY)
3839	return 0;
3840	return written;
3841	}
3842
3843	written = mapping->a_ops->direct_IO(iocb, from);
3844
3845	/*
3846	* Finally, try again to invalidate clean pages which might have been
3847	* cached by non-direct readahead, or faulted in by get_user_pages()
3848	* if the source of the write was an mmap'ed region of the file
3849	* we're writing. Either one is a pretty crazy thing to do,
3850	* so we don't support it 100%. If this invalidation
3851	* fails, tough, the write still worked...
3852	*
3853	* Most of the time we do not need this since dio_complete() will do
3854	* the invalidation for us. However there are some file systems that
3855	* do not end up with dio_complete() being called, so let's not break
3856	* them by removing it completely.
3857	*
3858	* Noticeable example is a blkdev_direct_IO().
3859	*
3860	* Skip invalidation for async writes or if mapping has no pages.
3861	*/
3862	if (written > 0) {
3863	struct inode *inode = mapping->host;
3864	loff_t pos = iocb->ki_pos;
3865
3866	kiocb_invalidate_post_direct_write(iocb, count: written);
3867	pos += written;
3868	write_len -= written;
3869	if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
3870	i_size_write(inode, i_size: pos);
3871	mark_inode_dirty(inode);
3872	}
3873	iocb->ki_pos = pos;
3874	}
3875	if (written != -EIOCBQUEUED)
3876	iov_iter_revert(i: from, bytes: write_len - iov_iter_count(i: from));
3877	return written;
3878	}
3879	EXPORT_SYMBOL(generic_file_direct_write);
3880
3881	ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
3882	{
3883	struct file *file = iocb->ki_filp;
3884	loff_t pos = iocb->ki_pos;
3885	struct address_space *mapping = file->f_mapping;
3886	const struct address_space_operations *a_ops = mapping->a_ops;
3887	long status = 0;
3888	ssize_t written = 0;
3889
3890	do {
3891	struct page *page;
3892	unsigned long offset; /* Offset into pagecache page */
3893	unsigned long bytes; /* Bytes to write to page */
3894	size_t copied; /* Bytes copied from user */
3895	void *fsdata = NULL;
3896
3897	offset = (pos & (PAGE_SIZE - 1));
3898	bytes = min_t(unsigned long, PAGE_SIZE - offset,
3899	iov_iter_count(i));
3900
3901	again:
3902	/*
3903	* Bring in the user page that we will copy from _first_.
3904	* Otherwise there's a nasty deadlock on copying from the
3905	* same page as we're writing to, without it being marked
3906	* up-to-date.
3907	*/
3908	if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
3909	status = -EFAULT;
3910	break;
3911	}
3912
3913	if (fatal_signal_pending(current)) {
3914	status = -EINTR;
3915	break;
3916	}
3917
3918	status = a_ops->write_begin(file, mapping, pos, bytes,
3919	&page, &fsdata);
3920	if (unlikely(status < 0))
3921	break;
3922
3923	if (mapping_writably_mapped(mapping))
3924	flush_dcache_page(page);
3925
3926	copied = copy_page_from_iter_atomic(page, offset, bytes, i);
3927	flush_dcache_page(page);
3928
3929	status = a_ops->write_end(file, mapping, pos, bytes, copied,
3930	page, fsdata);
3931	if (unlikely(status != copied)) {
3932	iov_iter_revert(i, bytes: copied - max(status, 0L));
3933	if (unlikely(status < 0))
3934	break;
3935	}
3936	cond_resched();
3937
3938	if (unlikely(status == 0)) {
3939	/*
3940	* A short copy made ->write_end() reject the
3941	* thing entirely. Might be memory poisoning
3942	* halfway through, might be a race with munmap,
3943	* might be severe memory pressure.
3944	*/
3945	if (copied)
3946	bytes = copied;
3947	goto again;
3948	}
3949	pos += status;
3950	written += status;
3951
3952	balance_dirty_pages_ratelimited(mapping);
3953	} while (iov_iter_count(i));
3954
3955	if (!written)
3956	return status;
3957	iocb->ki_pos += written;
3958	return written;
3959	}
3960	EXPORT_SYMBOL(generic_perform_write);
3961
3962	/**
3963	* __generic_file_write_iter - write data to a file
3964	* @iocb: IO state structure (file, offset, etc.)
3965	* @from: iov_iter with data to write
3966	*
3967	* This function does all the work needed for actually writing data to a
3968	* file. It does all basic checks, removes SUID from the file, updates
3969	* modification times and calls proper subroutines depending on whether we
3970	* do direct IO or a standard buffered write.
3971	*
3972	* It expects i_rwsem to be grabbed unless we work on a block device or similar
3973	* object which does not need locking at all.
3974	*
3975	* This function does *not* take care of syncing data in case of O_SYNC write.
3976	* A caller has to handle it. This is mainly due to the fact that we want to
3977	* avoid syncing under i_rwsem.
3978	*
3979	* Return:
3980	* * number of bytes written, even for truncated writes
3981	* * negative error code if no data has been written at all
3982	*/
3983	ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3984	{
3985	struct file *file = iocb->ki_filp;
3986	struct address_space *mapping = file->f_mapping;
3987	struct inode *inode = mapping->host;
3988	ssize_t ret;
3989
3990	ret = file_remove_privs(file);
3991	if (ret)
3992	return ret;
3993
3994	ret = file_update_time(file);
3995	if (ret)
3996	return ret;
3997
3998	if (iocb->ki_flags & IOCB_DIRECT) {
3999	ret = generic_file_direct_write(iocb, from);
4000	/*
4001	* If the write stopped short of completing, fall back to
4002	* buffered writes. Some filesystems do this for writes to
4003	* holes, for example. For DAX files, a buffered write will
4004	* not succeed (even if it did, DAX does not handle dirty
4005	* page-cache pages correctly).
4006	*/
4007	if (ret < 0 || !iov_iter_count(i: from) || IS_DAX(inode))
4008	return ret;
4009	return direct_write_fallback(iocb, iter: from, direct_written: ret,
4010	buffered_written: generic_perform_write(iocb, from));
4011	}
4012
4013	return generic_perform_write(iocb, from);
4014	}
4015	EXPORT_SYMBOL(__generic_file_write_iter);
4016
4017	/**
4018	* generic_file_write_iter - write data to a file
4019	* @iocb: IO state structure
4020	* @from: iov_iter with data to write
4021	*
4022	* This is a wrapper around __generic_file_write_iter() to be used by most
4023	* filesystems. It takes care of syncing the file in case of O_SYNC file
4024	* and acquires i_rwsem as needed.
4025	* Return:
4026	* * negative error code if no data has been written at all of
4027	* vfs_fsync_range() failed for a synchronous write
4028	* * number of bytes written, even for truncated writes
4029	*/
4030	ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
4031	{
4032	struct file *file = iocb->ki_filp;
4033	struct inode *inode = file->f_mapping->host;
4034	ssize_t ret;
4035
4036	inode_lock(inode);
4037	ret = generic_write_checks(iocb, from);
4038	if (ret > 0)
4039	ret = __generic_file_write_iter(iocb, from);
4040	inode_unlock(inode);
4041
4042	if (ret > 0)
4043	ret = generic_write_sync(iocb, count: ret);
4044	return ret;
4045	}
4046	EXPORT_SYMBOL(generic_file_write_iter);
4047
4048	/**
4049	* filemap_release_folio() - Release fs-specific metadata on a folio.
4050	* @folio: The folio which the kernel is trying to free.
4051	* @gfp: Memory allocation flags (and I/O mode).
4052	*
4053	* The address_space is trying to release any data attached to a folio
4054	* (presumably at folio->private).
4055	*
4056	* This will also be called if the private_2 flag is set on a page,
4057	* indicating that the folio has other metadata associated with it.
4058	*
4059	* The @gfp argument specifies whether I/O may be performed to release
4060	* this page (__GFP_IO), and whether the call may block
4061	* (__GFP_RECLAIM & __GFP_FS).
4062	*
4063	* Return: %true if the release was successful, otherwise %false.
4064	*/
4065	bool filemap_release_folio(struct folio *folio, gfp_t gfp)
4066	{
4067	struct address_space * const mapping = folio->mapping;
4068
4069	BUG_ON(!folio_test_locked(folio));
4070	if (!folio_needs_release(folio))
4071	return true;
4072	if (folio_test_writeback(folio))
4073	return false;
4074
4075	if (mapping && mapping->a_ops->release_folio)
4076	return mapping->a_ops->release_folio(folio, gfp);
4077	return try_to_free_buffers(folio);
4078	}
4079	EXPORT_SYMBOL(filemap_release_folio);
4080
4081	#ifdef CONFIG_CACHESTAT_SYSCALL
4082	/**
4083	* filemap_cachestat() - compute the page cache statistics of a mapping
4084	* @mapping: The mapping to compute the statistics for.
4085	* @first_index: The starting page cache index.
4086	* @last_index: The final page index (inclusive).
4087	* @cs: the cachestat struct to write the result to.
4088	*
4089	* This will query the page cache statistics of a mapping in the
4090	* page range of [first_index, last_index] (inclusive). The statistics
4091	* queried include: number of dirty pages, number of pages marked for
4092	* writeback, and the number of (recently) evicted pages.
4093	*/
4094	static void filemap_cachestat(struct address_space *mapping,
4095	pgoff_t first_index, pgoff_t last_index, struct cachestat *cs)
4096	{
4097	XA_STATE(xas, &mapping->i_pages, first_index);
4098	struct folio *folio;
4099
4100	rcu_read_lock();
4101	xas_for_each(&xas, folio, last_index) {
4102	unsigned long nr_pages;
4103	pgoff_t folio_first_index, folio_last_index;
4104
4105	if (xas_retry(xas: &xas, entry: folio))
4106	continue;
4107
4108	if (xa_is_value(entry: folio)) {
4109	/* page is evicted */
4110	void *shadow = (void *)folio;
4111	bool workingset; /* not used */
4112	int order = xa_get_order(xas.xa, index: xas.xa_index);
4113
4114	nr_pages = 1 << order;
4115	folio_first_index = round_down(xas.xa_index, 1 << order);
4116	folio_last_index = folio_first_index + nr_pages - 1;
4117
4118	/* Folios might straddle the range boundaries, only count covered pages */
4119	if (folio_first_index < first_index)
4120	nr_pages -= first_index - folio_first_index;
4121
4122	if (folio_last_index > last_index)
4123	nr_pages -= folio_last_index - last_index;
4124
4125	cs->nr_evicted += nr_pages;
4126
4127	#ifdef CONFIG_SWAP /* implies CONFIG_MMU */
4128	if (shmem_mapping(mapping)) {
4129	/* shmem file - in swap cache */
4130	swp_entry_t swp = radix_to_swp_entry(arg: folio);
4131
4132	shadow = get_shadow_from_swap_cache(entry: swp);
4133	}
4134	#endif
4135	if (workingset_test_recent(shadow, file: true, workingset: &workingset))
4136	cs->nr_recently_evicted += nr_pages;
4137
4138	goto resched;
4139	}
4140
4141	nr_pages = folio_nr_pages(folio);
4142	folio_first_index = folio_pgoff(folio);
4143	folio_last_index = folio_first_index + nr_pages - 1;
4144
4145	/* Folios might straddle the range boundaries, only count covered pages */
4146	if (folio_first_index < first_index)
4147	nr_pages -= first_index - folio_first_index;
4148
4149	if (folio_last_index > last_index)
4150	nr_pages -= folio_last_index - last_index;
4151
4152	/* page is in cache */
4153	cs->nr_cache += nr_pages;
4154
4155	if (folio_test_dirty(folio))
4156	cs->nr_dirty += nr_pages;
4157
4158	if (folio_test_writeback(folio))
4159	cs->nr_writeback += nr_pages;
4160
4161	resched:
4162	if (need_resched()) {
4163	xas_pause(&xas);
4164	cond_resched_rcu();
4165	}
4166	}
4167	rcu_read_unlock();
4168	}
4169
4170	/*
4171	* The cachestat(2) system call.
4172	*
4173	* cachestat() returns the page cache statistics of a file in the
4174	* bytes range specified by `off` and `len`: number of cached pages,
4175	* number of dirty pages, number of pages marked for writeback,
4176	* number of evicted pages, and number of recently evicted pages.
4177	*
4178	* An evicted page is a page that is previously in the page cache
4179	* but has been evicted since. A page is recently evicted if its last
4180	* eviction was recent enough that its reentry to the cache would
4181	* indicate that it is actively being used by the system, and that
4182	* there is memory pressure on the system.
4183	*
4184	* `off` and `len` must be non-negative integers. If `len` > 0,
4185	* the queried range is [`off`, `off` + `len`]. If `len` == 0,
4186	* we will query in the range from `off` to the end of the file.
4187	*
4188	* The `flags` argument is unused for now, but is included for future
4189	* extensibility. User should pass 0 (i.e no flag specified).
4190	*
4191	* Currently, hugetlbfs is not supported.
4192	*
4193	* Because the status of a page can change after cachestat() checks it
4194	* but before it returns to the application, the returned values may
4195	* contain stale information.
4196	*
4197	* return values:
4198	* zero - success
4199	* -EFAULT - cstat or cstat_range points to an illegal address
4200	* -EINVAL - invalid flags
4201	* -EBADF - invalid file descriptor
4202	* -EOPNOTSUPP - file descriptor is of a hugetlbfs file
4203	*/
4204	SYSCALL_DEFINE4(cachestat, unsigned int, fd,
4205	struct cachestat_range __user *, cstat_range,
4206	struct cachestat __user *, cstat, unsigned int, flags)
4207	{
4208	struct fd f = fdget(fd);
4209	struct address_space *mapping;
4210	struct cachestat_range csr;
4211	struct cachestat cs;
4212	pgoff_t first_index, last_index;
4213
4214	if (!f.file)
4215	return -EBADF;
4216
4217	if (copy_from_user(to: &csr, from: cstat_range,
4218	n: sizeof(struct cachestat_range))) {
4219	fdput(fd: f);
4220	return -EFAULT;
4221	}
4222
4223	/* hugetlbfs is not supported */
4224	if (is_file_hugepages(file: f.file)) {
4225	fdput(fd: f);
4226	return -EOPNOTSUPP;
4227	}
4228
4229	if (flags != 0) {
4230	fdput(fd: f);
4231	return -EINVAL;
4232	}
4233
4234	first_index = csr.off >> PAGE_SHIFT;
4235	last_index =
4236	csr.len == 0 ? ULONG_MAX : (csr.off + csr.len - 1) >> PAGE_SHIFT;
4237	memset(&cs, 0, sizeof(struct cachestat));
4238	mapping = f.file->f_mapping;
4239	filemap_cachestat(mapping, first_index, last_index, cs: &cs);
4240	fdput(fd: f);
4241
4242	if (copy_to_user(to: cstat, from: &cs, n: sizeof(struct cachestat)))
4243	return -EFAULT;
4244
4245	return 0;
4246	}
4247	#endif /* CONFIG_CACHESTAT_SYSCALL */
4248