1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/ext4/file.c
4 *
5 * Copyright (C) 1992, 1993, 1994, 1995
6 * Remy Card (card@masi.ibp.fr)
7 * Laboratoire MASI - Institut Blaise Pascal
8 * Universite Pierre et Marie Curie (Paris VI)
9 *
10 * from
11 *
12 * linux/fs/minix/file.c
13 *
14 * Copyright (C) 1991, 1992 Linus Torvalds
15 *
16 * ext4 fs regular file handling primitives
17 *
18 * 64-bit file support on 64-bit platforms by Jakub Jelinek
19 * (jj@sunsite.ms.mff.cuni.cz)
20 */
21
22#include <linux/time.h>
23#include <linux/fs.h>
24#include <linux/iomap.h>
25#include <linux/mount.h>
26#include <linux/path.h>
27#include <linux/dax.h>
28#include <linux/quotaops.h>
29#include <linux/pagevec.h>
30#include <linux/uio.h>
31#include <linux/mman.h>
32#include <linux/backing-dev.h>
33#include "ext4.h"
34#include "ext4_jbd2.h"
35#include "xattr.h"
36#include "acl.h"
37#include "truncate.h"
38
39/*
40 * Returns %true if the given DIO request should be attempted with DIO, or
41 * %false if it should fall back to buffered I/O.
42 *
43 * DIO isn't well specified; when it's unsupported (either due to the request
44 * being misaligned, or due to the file not supporting DIO at all), filesystems
45 * either fall back to buffered I/O or return EINVAL. For files that don't use
46 * any special features like encryption or verity, ext4 has traditionally
47 * returned EINVAL for misaligned DIO. iomap_dio_rw() uses this convention too.
48 * In this case, we should attempt the DIO, *not* fall back to buffered I/O.
49 *
50 * In contrast, in cases where DIO is unsupported due to ext4 features, ext4
51 * traditionally falls back to buffered I/O.
52 *
53 * This function implements the traditional ext4 behavior in all these cases.
54 */
55static bool ext4_should_use_dio(struct kiocb *iocb, struct iov_iter *iter)
56{
57 struct inode *inode = file_inode(f: iocb->ki_filp);
58 u32 dio_align = ext4_dio_alignment(inode);
59
60 if (dio_align == 0)
61 return false;
62
63 if (dio_align == 1)
64 return true;
65
66 return IS_ALIGNED(iocb->ki_pos | iov_iter_alignment(iter), dio_align);
67}
68
69static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
70{
71 ssize_t ret;
72 struct inode *inode = file_inode(f: iocb->ki_filp);
73
74 if (iocb->ki_flags & IOCB_NOWAIT) {
75 if (!inode_trylock_shared(inode))
76 return -EAGAIN;
77 } else {
78 inode_lock_shared(inode);
79 }
80
81 if (!ext4_should_use_dio(iocb, iter: to)) {
82 inode_unlock_shared(inode);
83 /*
84 * Fallback to buffered I/O if the operation being performed on
85 * the inode is not supported by direct I/O. The IOCB_DIRECT
86 * flag needs to be cleared here in order to ensure that the
87 * direct I/O path within generic_file_read_iter() is not
88 * taken.
89 */
90 iocb->ki_flags &= ~IOCB_DIRECT;
91 return generic_file_read_iter(iocb, to);
92 }
93
94 ret = iomap_dio_rw(iocb, iter: to, ops: &ext4_iomap_ops, NULL, dio_flags: 0, NULL, done_before: 0);
95 inode_unlock_shared(inode);
96
97 file_accessed(file: iocb->ki_filp);
98 return ret;
99}
100
101#ifdef CONFIG_FS_DAX
102static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
103{
104 struct inode *inode = file_inode(f: iocb->ki_filp);
105 ssize_t ret;
106
107 if (iocb->ki_flags & IOCB_NOWAIT) {
108 if (!inode_trylock_shared(inode))
109 return -EAGAIN;
110 } else {
111 inode_lock_shared(inode);
112 }
113 /*
114 * Recheck under inode lock - at this point we are sure it cannot
115 * change anymore
116 */
117 if (!IS_DAX(inode)) {
118 inode_unlock_shared(inode);
119 /* Fallback to buffered IO in case we cannot support DAX */
120 return generic_file_read_iter(iocb, to);
121 }
122 ret = dax_iomap_rw(iocb, iter: to, ops: &ext4_iomap_ops);
123 inode_unlock_shared(inode);
124
125 file_accessed(file: iocb->ki_filp);
126 return ret;
127}
128#endif
129
130static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
131{
132 struct inode *inode = file_inode(f: iocb->ki_filp);
133
134 if (unlikely(ext4_forced_shutdown(inode->i_sb)))
135 return -EIO;
136
137 if (!iov_iter_count(i: to))
138 return 0; /* skip atime */
139
140#ifdef CONFIG_FS_DAX
141 if (IS_DAX(inode))
142 return ext4_dax_read_iter(iocb, to);
143#endif
144 if (iocb->ki_flags & IOCB_DIRECT)
145 return ext4_dio_read_iter(iocb, to);
146
147 return generic_file_read_iter(iocb, to);
148}
149
150static ssize_t ext4_file_splice_read(struct file *in, loff_t *ppos,
151 struct pipe_inode_info *pipe,
152 size_t len, unsigned int flags)
153{
154 struct inode *inode = file_inode(f: in);
155
156 if (unlikely(ext4_forced_shutdown(inode->i_sb)))
157 return -EIO;
158 return filemap_splice_read(in, ppos, pipe, len, flags);
159}
160
161/*
162 * Called when an inode is released. Note that this is different
163 * from ext4_file_open: open gets called at every open, but release
164 * gets called only when /all/ the files are closed.
165 */
166static int ext4_release_file(struct inode *inode, struct file *filp)
167{
168 if (ext4_test_inode_state(inode, bit: EXT4_STATE_DA_ALLOC_CLOSE)) {
169 ext4_alloc_da_blocks(inode);
170 ext4_clear_inode_state(inode, bit: EXT4_STATE_DA_ALLOC_CLOSE);
171 }
172 /* if we are the last writer on the inode, drop the block reservation */
173 if ((filp->f_mode & FMODE_WRITE) &&
174 (atomic_read(v: &inode->i_writecount) == 1) &&
175 !EXT4_I(inode)->i_reserved_data_blocks) {
176 down_write(sem: &EXT4_I(inode)->i_data_sem);
177 ext4_discard_preallocations(inode, 0);
178 up_write(sem: &EXT4_I(inode)->i_data_sem);
179 }
180 if (is_dx(inode) && filp->private_data)
181 ext4_htree_free_dir_info(p: filp->private_data);
182
183 return 0;
184}
185
186/*
187 * This tests whether the IO in question is block-aligned or not.
188 * Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
189 * are converted to written only after the IO is complete. Until they are
190 * mapped, these blocks appear as holes, so dio_zero_block() will assume that
191 * it needs to zero out portions of the start and/or end block. If 2 AIO
192 * threads are at work on the same unwritten block, they must be synchronized
193 * or one thread will zero the other's data, causing corruption.
194 */
195static bool
196ext4_unaligned_io(struct inode *inode, struct iov_iter *from, loff_t pos)
197{
198 struct super_block *sb = inode->i_sb;
199 unsigned long blockmask = sb->s_blocksize - 1;
200
201 if ((pos | iov_iter_alignment(i: from)) & blockmask)
202 return true;
203
204 return false;
205}
206
207static bool
208ext4_extending_io(struct inode *inode, loff_t offset, size_t len)
209{
210 if (offset + len > i_size_read(inode) ||
211 offset + len > EXT4_I(inode)->i_disksize)
212 return true;
213 return false;
214}
215
216/* Is IO overwriting allocated or initialized blocks? */
217static bool ext4_overwrite_io(struct inode *inode,
218 loff_t pos, loff_t len, bool *unwritten)
219{
220 struct ext4_map_blocks map;
221 unsigned int blkbits = inode->i_blkbits;
222 int err, blklen;
223
224 if (pos + len > i_size_read(inode))
225 return false;
226
227 map.m_lblk = pos >> blkbits;
228 map.m_len = EXT4_MAX_BLOCKS(len, pos, blkbits);
229 blklen = map.m_len;
230
231 err = ext4_map_blocks(NULL, inode, map: &map, flags: 0);
232 if (err != blklen)
233 return false;
234 /*
235 * 'err==len' means that all of the blocks have been preallocated,
236 * regardless of whether they have been initialized or not. We need to
237 * check m_flags to distinguish the unwritten extents.
238 */
239 *unwritten = !(map.m_flags & EXT4_MAP_MAPPED);
240 return true;
241}
242
243static ssize_t ext4_generic_write_checks(struct kiocb *iocb,
244 struct iov_iter *from)
245{
246 struct inode *inode = file_inode(f: iocb->ki_filp);
247 ssize_t ret;
248
249 if (unlikely(IS_IMMUTABLE(inode)))
250 return -EPERM;
251
252 ret = generic_write_checks(iocb, from);
253 if (ret <= 0)
254 return ret;
255
256 /*
257 * If we have encountered a bitmap-format file, the size limit
258 * is smaller than s_maxbytes, which is for extent-mapped files.
259 */
260 if (!(ext4_test_inode_flag(inode, bit: EXT4_INODE_EXTENTS))) {
261 struct ext4_sb_info *sbi = EXT4_SB(sb: inode->i_sb);
262
263 if (iocb->ki_pos >= sbi->s_bitmap_maxbytes)
264 return -EFBIG;
265 iov_iter_truncate(i: from, count: sbi->s_bitmap_maxbytes - iocb->ki_pos);
266 }
267
268 return iov_iter_count(i: from);
269}
270
271static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
272{
273 ssize_t ret, count;
274
275 count = ext4_generic_write_checks(iocb, from);
276 if (count <= 0)
277 return count;
278
279 ret = file_modified(file: iocb->ki_filp);
280 if (ret)
281 return ret;
282 return count;
283}
284
285static ssize_t ext4_buffered_write_iter(struct kiocb *iocb,
286 struct iov_iter *from)
287{
288 ssize_t ret;
289 struct inode *inode = file_inode(f: iocb->ki_filp);
290
291 if (iocb->ki_flags & IOCB_NOWAIT)
292 return -EOPNOTSUPP;
293
294 inode_lock(inode);
295 ret = ext4_write_checks(iocb, from);
296 if (ret <= 0)
297 goto out;
298
299 ret = generic_perform_write(iocb, from);
300
301out:
302 inode_unlock(inode);
303 if (unlikely(ret <= 0))
304 return ret;
305 return generic_write_sync(iocb, count: ret);
306}
307
308static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
309 ssize_t count)
310{
311 handle_t *handle;
312
313 lockdep_assert_held_write(&inode->i_rwsem);
314 handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
315 if (IS_ERR(ptr: handle))
316 return PTR_ERR(ptr: handle);
317
318 if (ext4_update_inode_size(inode, newsize: offset + count)) {
319 int ret = ext4_mark_inode_dirty(handle, inode);
320 if (unlikely(ret)) {
321 ext4_journal_stop(handle);
322 return ret;
323 }
324 }
325
326 if (inode->i_nlink)
327 ext4_orphan_del(handle, inode);
328 ext4_journal_stop(handle);
329
330 return count;
331}
332
333/*
334 * Clean up the inode after DIO or DAX extending write has completed and the
335 * inode size has been updated using ext4_handle_inode_extension().
336 */
337static void ext4_inode_extension_cleanup(struct inode *inode, ssize_t count)
338{
339 lockdep_assert_held_write(&inode->i_rwsem);
340 if (count < 0) {
341 ext4_truncate_failed_write(inode);
342 /*
343 * If the truncate operation failed early, then the inode may
344 * still be on the orphan list. In that case, we need to try
345 * remove the inode from the in-memory linked list.
346 */
347 if (inode->i_nlink)
348 ext4_orphan_del(NULL, inode);
349 return;
350 }
351 /*
352 * If i_disksize got extended due to writeback of delalloc blocks while
353 * the DIO was running we could fail to cleanup the orphan list in
354 * ext4_handle_inode_extension(). Do it now.
355 */
356 if (!list_empty(head: &EXT4_I(inode)->i_orphan) && inode->i_nlink) {
357 handle_t *handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
358
359 if (IS_ERR(ptr: handle)) {
360 /*
361 * The write has successfully completed. Not much to
362 * do with the error here so just cleanup the orphan
363 * list and hope for the best.
364 */
365 ext4_orphan_del(NULL, inode);
366 return;
367 }
368 ext4_orphan_del(handle, inode);
369 ext4_journal_stop(handle);
370 }
371}
372
373static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
374 int error, unsigned int flags)
375{
376 loff_t pos = iocb->ki_pos;
377 struct inode *inode = file_inode(f: iocb->ki_filp);
378
379 if (!error && size && flags & IOMAP_DIO_UNWRITTEN)
380 error = ext4_convert_unwritten_extents(NULL, inode, offset: pos, len: size);
381 if (error)
382 return error;
383 /*
384 * Note that EXT4_I(inode)->i_disksize can get extended up to
385 * inode->i_size while the I/O was running due to writeback of delalloc
386 * blocks. But the code in ext4_iomap_alloc() is careful to use
387 * zeroed/unwritten extents if this is possible; thus we won't leave
388 * uninitialized blocks in a file even if we didn't succeed in writing
389 * as much as we intended.
390 */
391 WARN_ON_ONCE(i_size_read(inode) < READ_ONCE(EXT4_I(inode)->i_disksize));
392 if (pos + size <= READ_ONCE(EXT4_I(inode)->i_disksize))
393 return size;
394 return ext4_handle_inode_extension(inode, offset: pos, count: size);
395}
396
397static const struct iomap_dio_ops ext4_dio_write_ops = {
398 .end_io = ext4_dio_write_end_io,
399};
400
401/*
402 * The intention here is to start with shared lock acquired then see if any
403 * condition requires an exclusive inode lock. If yes, then we restart the
404 * whole operation by releasing the shared lock and acquiring exclusive lock.
405 *
406 * - For unaligned_io we never take shared lock as it may cause data corruption
407 * when two unaligned IO tries to modify the same block e.g. while zeroing.
408 *
409 * - For extending writes case we don't take the shared lock, since it requires
410 * updating inode i_disksize and/or orphan handling with exclusive lock.
411 *
412 * - shared locking will only be true mostly with overwrites, including
413 * initialized blocks and unwritten blocks. For overwrite unwritten blocks
414 * we protect splitting extents by i_data_sem in ext4_inode_info, so we can
415 * also release exclusive i_rwsem lock.
416 *
417 * - Otherwise we will switch to exclusive i_rwsem lock.
418 */
419static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from,
420 bool *ilock_shared, bool *extend,
421 bool *unwritten, int *dio_flags)
422{
423 struct file *file = iocb->ki_filp;
424 struct inode *inode = file_inode(f: file);
425 loff_t offset;
426 size_t count;
427 ssize_t ret;
428 bool overwrite, unaligned_io;
429
430restart:
431 ret = ext4_generic_write_checks(iocb, from);
432 if (ret <= 0)
433 goto out;
434
435 offset = iocb->ki_pos;
436 count = ret;
437
438 unaligned_io = ext4_unaligned_io(inode, from, pos: offset);
439 *extend = ext4_extending_io(inode, offset, len: count);
440 overwrite = ext4_overwrite_io(inode, pos: offset, len: count, unwritten);
441
442 /*
443 * Determine whether we need to upgrade to an exclusive lock. This is
444 * required to change security info in file_modified(), for extending
445 * I/O, any form of non-overwrite I/O, and unaligned I/O to unwritten
446 * extents (as partial block zeroing may be required).
447 *
448 * Note that unaligned writes are allowed under shared lock so long as
449 * they are pure overwrites. Otherwise, concurrent unaligned writes risk
450 * data corruption due to partial block zeroing in the dio layer, and so
451 * the I/O must occur exclusively.
452 */
453 if (*ilock_shared &&
454 ((!IS_NOSEC(inode) || *extend || !overwrite ||
455 (unaligned_io && *unwritten)))) {
456 if (iocb->ki_flags & IOCB_NOWAIT) {
457 ret = -EAGAIN;
458 goto out;
459 }
460 inode_unlock_shared(inode);
461 *ilock_shared = false;
462 inode_lock(inode);
463 goto restart;
464 }
465
466 /*
467 * Now that locking is settled, determine dio flags and exclusivity
468 * requirements. We don't use DIO_OVERWRITE_ONLY because we enforce
469 * behavior already. The inode lock is already held exclusive if the
470 * write is non-overwrite or extending, so drain all outstanding dio and
471 * set the force wait dio flag.
472 */
473 if (!*ilock_shared && (unaligned_io || *extend)) {
474 if (iocb->ki_flags & IOCB_NOWAIT) {
475 ret = -EAGAIN;
476 goto out;
477 }
478 if (unaligned_io && (!overwrite || *unwritten))
479 inode_dio_wait(inode);
480 *dio_flags = IOMAP_DIO_FORCE_WAIT;
481 }
482
483 ret = file_modified(file);
484 if (ret < 0)
485 goto out;
486
487 return count;
488out:
489 if (*ilock_shared)
490 inode_unlock_shared(inode);
491 else
492 inode_unlock(inode);
493 return ret;
494}
495
496static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
497{
498 ssize_t ret;
499 handle_t *handle;
500 struct inode *inode = file_inode(f: iocb->ki_filp);
501 loff_t offset = iocb->ki_pos;
502 size_t count = iov_iter_count(i: from);
503 const struct iomap_ops *iomap_ops = &ext4_iomap_ops;
504 bool extend = false, unwritten = false;
505 bool ilock_shared = true;
506 int dio_flags = 0;
507
508 /*
509 * Quick check here without any i_rwsem lock to see if it is extending
510 * IO. A more reliable check is done in ext4_dio_write_checks() with
511 * proper locking in place.
512 */
513 if (offset + count > i_size_read(inode))
514 ilock_shared = false;
515
516 if (iocb->ki_flags & IOCB_NOWAIT) {
517 if (ilock_shared) {
518 if (!inode_trylock_shared(inode))
519 return -EAGAIN;
520 } else {
521 if (!inode_trylock(inode))
522 return -EAGAIN;
523 }
524 } else {
525 if (ilock_shared)
526 inode_lock_shared(inode);
527 else
528 inode_lock(inode);
529 }
530
531 /* Fallback to buffered I/O if the inode does not support direct I/O. */
532 if (!ext4_should_use_dio(iocb, iter: from)) {
533 if (ilock_shared)
534 inode_unlock_shared(inode);
535 else
536 inode_unlock(inode);
537 return ext4_buffered_write_iter(iocb, from);
538 }
539
540 /*
541 * Prevent inline data from being created since we are going to allocate
542 * blocks for DIO. We know the inode does not currently have inline data
543 * because ext4_should_use_dio() checked for it, but we have to clear
544 * the state flag before the write checks because a lock cycle could
545 * introduce races with other writers.
546 */
547 ext4_clear_inode_state(inode, bit: EXT4_STATE_MAY_INLINE_DATA);
548
549 ret = ext4_dio_write_checks(iocb, from, ilock_shared: &ilock_shared, extend: &extend,
550 unwritten: &unwritten, dio_flags: &dio_flags);
551 if (ret <= 0)
552 return ret;
553
554 offset = iocb->ki_pos;
555 count = ret;
556
557 if (extend) {
558 handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
559 if (IS_ERR(ptr: handle)) {
560 ret = PTR_ERR(ptr: handle);
561 goto out;
562 }
563
564 ret = ext4_orphan_add(handle, inode);
565 if (ret) {
566 ext4_journal_stop(handle);
567 goto out;
568 }
569
570 ext4_journal_stop(handle);
571 }
572
573 if (ilock_shared && !unwritten)
574 iomap_ops = &ext4_iomap_overwrite_ops;
575 ret = iomap_dio_rw(iocb, iter: from, ops: iomap_ops, dops: &ext4_dio_write_ops,
576 dio_flags, NULL, done_before: 0);
577 if (ret == -ENOTBLK)
578 ret = 0;
579 if (extend) {
580 /*
581 * We always perform extending DIO write synchronously so by
582 * now the IO is completed and ext4_handle_inode_extension()
583 * was called. Cleanup the inode in case of error or race with
584 * writeback of delalloc blocks.
585 */
586 WARN_ON_ONCE(ret == -EIOCBQUEUED);
587 ext4_inode_extension_cleanup(inode, count: ret);
588 }
589
590out:
591 if (ilock_shared)
592 inode_unlock_shared(inode);
593 else
594 inode_unlock(inode);
595
596 if (ret >= 0 && iov_iter_count(i: from)) {
597 ssize_t err;
598 loff_t endbyte;
599
600 offset = iocb->ki_pos;
601 err = ext4_buffered_write_iter(iocb, from);
602 if (err < 0)
603 return err;
604
605 /*
606 * We need to ensure that the pages within the page cache for
607 * the range covered by this I/O are written to disk and
608 * invalidated. This is in attempt to preserve the expected
609 * direct I/O semantics in the case we fallback to buffered I/O
610 * to complete off the I/O request.
611 */
612 ret += err;
613 endbyte = offset + err - 1;
614 err = filemap_write_and_wait_range(mapping: iocb->ki_filp->f_mapping,
615 lstart: offset, lend: endbyte);
616 if (!err)
617 invalidate_mapping_pages(mapping: iocb->ki_filp->f_mapping,
618 start: offset >> PAGE_SHIFT,
619 end: endbyte >> PAGE_SHIFT);
620 }
621
622 return ret;
623}
624
625#ifdef CONFIG_FS_DAX
626static ssize_t
627ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
628{
629 ssize_t ret;
630 size_t count;
631 loff_t offset;
632 handle_t *handle;
633 bool extend = false;
634 struct inode *inode = file_inode(f: iocb->ki_filp);
635
636 if (iocb->ki_flags & IOCB_NOWAIT) {
637 if (!inode_trylock(inode))
638 return -EAGAIN;
639 } else {
640 inode_lock(inode);
641 }
642
643 ret = ext4_write_checks(iocb, from);
644 if (ret <= 0)
645 goto out;
646
647 offset = iocb->ki_pos;
648 count = iov_iter_count(i: from);
649
650 if (offset + count > EXT4_I(inode)->i_disksize) {
651 handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
652 if (IS_ERR(ptr: handle)) {
653 ret = PTR_ERR(ptr: handle);
654 goto out;
655 }
656
657 ret = ext4_orphan_add(handle, inode);
658 if (ret) {
659 ext4_journal_stop(handle);
660 goto out;
661 }
662
663 extend = true;
664 ext4_journal_stop(handle);
665 }
666
667 ret = dax_iomap_rw(iocb, iter: from, ops: &ext4_iomap_ops);
668
669 if (extend) {
670 ret = ext4_handle_inode_extension(inode, offset, count: ret);
671 ext4_inode_extension_cleanup(inode, count: ret);
672 }
673out:
674 inode_unlock(inode);
675 if (ret > 0)
676 ret = generic_write_sync(iocb, count: ret);
677 return ret;
678}
679#endif
680
681static ssize_t
682ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
683{
684 struct inode *inode = file_inode(f: iocb->ki_filp);
685
686 if (unlikely(ext4_forced_shutdown(inode->i_sb)))
687 return -EIO;
688
689#ifdef CONFIG_FS_DAX
690 if (IS_DAX(inode))
691 return ext4_dax_write_iter(iocb, from);
692#endif
693 if (iocb->ki_flags & IOCB_DIRECT)
694 return ext4_dio_write_iter(iocb, from);
695 else
696 return ext4_buffered_write_iter(iocb, from);
697}
698
699#ifdef CONFIG_FS_DAX
700static vm_fault_t ext4_dax_huge_fault(struct vm_fault *vmf, unsigned int order)
701{
702 int error = 0;
703 vm_fault_t result;
704 int retries = 0;
705 handle_t *handle = NULL;
706 struct inode *inode = file_inode(f: vmf->vma->vm_file);
707 struct super_block *sb = inode->i_sb;
708
709 /*
710 * We have to distinguish real writes from writes which will result in a
711 * COW page; COW writes should *not* poke the journal (the file will not
712 * be changed). Doing so would cause unintended failures when mounted
713 * read-only.
714 *
715 * We check for VM_SHARED rather than vmf->cow_page since the latter is
716 * unset for order != 0 (i.e. only in do_cow_fault); for
717 * other sizes, dax_iomap_fault will handle splitting / fallback so that
718 * we eventually come back with a COW page.
719 */
720 bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
721 (vmf->vma->vm_flags & VM_SHARED);
722 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
723 pfn_t pfn;
724
725 if (write) {
726 sb_start_pagefault(sb);
727 file_update_time(file: vmf->vma->vm_file);
728 filemap_invalidate_lock_shared(mapping);
729retry:
730 handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
731 EXT4_DATA_TRANS_BLOCKS(sb));
732 if (IS_ERR(ptr: handle)) {
733 filemap_invalidate_unlock_shared(mapping);
734 sb_end_pagefault(sb);
735 return VM_FAULT_SIGBUS;
736 }
737 } else {
738 filemap_invalidate_lock_shared(mapping);
739 }
740 result = dax_iomap_fault(vmf, order, pfnp: &pfn, errp: &error, ops: &ext4_iomap_ops);
741 if (write) {
742 ext4_journal_stop(handle);
743
744 if ((result & VM_FAULT_ERROR) && error == -ENOSPC &&
745 ext4_should_retry_alloc(sb, retries: &retries))
746 goto retry;
747 /* Handling synchronous page fault? */
748 if (result & VM_FAULT_NEEDDSYNC)
749 result = dax_finish_sync_fault(vmf, order, pfn);
750 filemap_invalidate_unlock_shared(mapping);
751 sb_end_pagefault(sb);
752 } else {
753 filemap_invalidate_unlock_shared(mapping);
754 }
755
756 return result;
757}
758
759static vm_fault_t ext4_dax_fault(struct vm_fault *vmf)
760{
761 return ext4_dax_huge_fault(vmf, order: 0);
762}
763
764static const struct vm_operations_struct ext4_dax_vm_ops = {
765 .fault = ext4_dax_fault,
766 .huge_fault = ext4_dax_huge_fault,
767 .page_mkwrite = ext4_dax_fault,
768 .pfn_mkwrite = ext4_dax_fault,
769};
770#else
771#define ext4_dax_vm_ops ext4_file_vm_ops
772#endif
773
774static const struct vm_operations_struct ext4_file_vm_ops = {
775 .fault = filemap_fault,
776 .map_pages = filemap_map_pages,
777 .page_mkwrite = ext4_page_mkwrite,
778};
779
780static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
781{
782 struct inode *inode = file->f_mapping->host;
783 struct dax_device *dax_dev = EXT4_SB(sb: inode->i_sb)->s_daxdev;
784
785 if (unlikely(ext4_forced_shutdown(inode->i_sb)))
786 return -EIO;
787
788 /*
789 * We don't support synchronous mappings for non-DAX files and
790 * for DAX files if underneath dax_device is not synchronous.
791 */
792 if (!daxdev_mapping_supported(vma, dax_dev))
793 return -EOPNOTSUPP;
794
795 file_accessed(file);
796 if (IS_DAX(file_inode(file))) {
797 vma->vm_ops = &ext4_dax_vm_ops;
798 vm_flags_set(vma, VM_HUGEPAGE);
799 } else {
800 vma->vm_ops = &ext4_file_vm_ops;
801 }
802 return 0;
803}
804
805static int ext4_sample_last_mounted(struct super_block *sb,
806 struct vfsmount *mnt)
807{
808 struct ext4_sb_info *sbi = EXT4_SB(sb);
809 struct path path;
810 char buf[64], *cp;
811 handle_t *handle;
812 int err;
813
814 if (likely(ext4_test_mount_flag(sb, EXT4_MF_MNTDIR_SAMPLED)))
815 return 0;
816
817 if (sb_rdonly(sb) || !sb_start_intwrite_trylock(sb))
818 return 0;
819
820 ext4_set_mount_flag(sb, bit: EXT4_MF_MNTDIR_SAMPLED);
821 /*
822 * Sample where the filesystem has been mounted and
823 * store it in the superblock for sysadmin convenience
824 * when trying to sort through large numbers of block
825 * devices or filesystem images.
826 */
827 memset(buf, 0, sizeof(buf));
828 path.mnt = mnt;
829 path.dentry = mnt->mnt_root;
830 cp = d_path(&path, buf, sizeof(buf));
831 err = 0;
832 if (IS_ERR(ptr: cp))
833 goto out;
834
835 handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
836 err = PTR_ERR(ptr: handle);
837 if (IS_ERR(ptr: handle))
838 goto out;
839 BUFFER_TRACE(sbi->s_sbh, "get_write_access");
840 err = ext4_journal_get_write_access(handle, sb, sbi->s_sbh,
841 EXT4_JTR_NONE);
842 if (err)
843 goto out_journal;
844 lock_buffer(bh: sbi->s_sbh);
845 strncpy(p: sbi->s_es->s_last_mounted, q: cp,
846 size: sizeof(sbi->s_es->s_last_mounted));
847 ext4_superblock_csum_set(sb);
848 unlock_buffer(bh: sbi->s_sbh);
849 ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);
850out_journal:
851 ext4_journal_stop(handle);
852out:
853 sb_end_intwrite(sb);
854 return err;
855}
856
857static int ext4_file_open(struct inode *inode, struct file *filp)
858{
859 int ret;
860
861 if (unlikely(ext4_forced_shutdown(inode->i_sb)))
862 return -EIO;
863
864 ret = ext4_sample_last_mounted(sb: inode->i_sb, mnt: filp->f_path.mnt);
865 if (ret)
866 return ret;
867
868 ret = fscrypt_file_open(inode, filp);
869 if (ret)
870 return ret;
871
872 ret = fsverity_file_open(inode, filp);
873 if (ret)
874 return ret;
875
876 /*
877 * Set up the jbd2_inode if we are opening the inode for
878 * writing and the journal is present
879 */
880 if (filp->f_mode & FMODE_WRITE) {
881 ret = ext4_inode_attach_jinode(inode);
882 if (ret < 0)
883 return ret;
884 }
885
886 filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC |
887 FMODE_DIO_PARALLEL_WRITE;
888 return dquot_file_open(inode, file: filp);
889}
890
891/*
892 * ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
893 * by calling generic_file_llseek_size() with the appropriate maxbytes
894 * value for each.
895 */
896loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
897{
898 struct inode *inode = file->f_mapping->host;
899 loff_t maxbytes;
900
901 if (!(ext4_test_inode_flag(inode, bit: EXT4_INODE_EXTENTS)))
902 maxbytes = EXT4_SB(sb: inode->i_sb)->s_bitmap_maxbytes;
903 else
904 maxbytes = inode->i_sb->s_maxbytes;
905
906 switch (whence) {
907 default:
908 return generic_file_llseek_size(file, offset, whence,
909 maxsize: maxbytes, eof: i_size_read(inode));
910 case SEEK_HOLE:
911 inode_lock_shared(inode);
912 offset = iomap_seek_hole(inode, offset,
913 ops: &ext4_iomap_report_ops);
914 inode_unlock_shared(inode);
915 break;
916 case SEEK_DATA:
917 inode_lock_shared(inode);
918 offset = iomap_seek_data(inode, offset,
919 ops: &ext4_iomap_report_ops);
920 inode_unlock_shared(inode);
921 break;
922 }
923
924 if (offset < 0)
925 return offset;
926 return vfs_setpos(file, offset, maxsize: maxbytes);
927}
928
929const struct file_operations ext4_file_operations = {
930 .llseek = ext4_llseek,
931 .read_iter = ext4_file_read_iter,
932 .write_iter = ext4_file_write_iter,
933 .iopoll = iocb_bio_iopoll,
934 .unlocked_ioctl = ext4_ioctl,
935#ifdef CONFIG_COMPAT
936 .compat_ioctl = ext4_compat_ioctl,
937#endif
938 .mmap = ext4_file_mmap,
939 .mmap_supported_flags = MAP_SYNC,
940 .open = ext4_file_open,
941 .release = ext4_release_file,
942 .fsync = ext4_sync_file,
943 .get_unmapped_area = thp_get_unmapped_area,
944 .splice_read = ext4_file_splice_read,
945 .splice_write = iter_file_splice_write,
946 .fallocate = ext4_fallocate,
947};
948
949const struct inode_operations ext4_file_inode_operations = {
950 .setattr = ext4_setattr,
951 .getattr = ext4_file_getattr,
952 .listxattr = ext4_listxattr,
953 .get_inode_acl = ext4_get_acl,
954 .set_acl = ext4_set_acl,
955 .fiemap = ext4_fiemap,
956 .fileattr_get = ext4_fileattr_get,
957 .fileattr_set = ext4_fileattr_set,
958};
959
960

source code of linux/fs/ext4/file.c