1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * linux/mm/page_io.c |
4 | * |
5 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
6 | * |
7 | * Swap reorganised 29.12.95, |
8 | * Asynchronous swapping added 30.12.95. Stephen Tweedie |
9 | * Removed race in async swapping. 14.4.1996. Bruno Haible |
10 | * Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie |
11 | * Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman |
12 | */ |
13 | |
14 | #include <linux/mm.h> |
15 | #include <linux/kernel_stat.h> |
16 | #include <linux/gfp.h> |
17 | #include <linux/pagemap.h> |
18 | #include <linux/swap.h> |
19 | #include <linux/bio.h> |
20 | #include <linux/swapops.h> |
21 | #include <linux/buffer_head.h> |
22 | #include <linux/writeback.h> |
23 | #include <linux/frontswap.h> |
24 | #include <linux/blkdev.h> |
25 | #include <linux/uio.h> |
26 | #include <linux/sched/task.h> |
27 | #include <asm/pgtable.h> |
28 | |
29 | static struct bio *get_swap_bio(gfp_t gfp_flags, |
30 | struct page *page, bio_end_io_t end_io) |
31 | { |
32 | int i, nr = hpage_nr_pages(page); |
33 | struct bio *bio; |
34 | |
35 | bio = bio_alloc(gfp_flags, nr); |
36 | if (bio) { |
37 | struct block_device *bdev; |
38 | |
39 | bio->bi_iter.bi_sector = map_swap_page(page, &bdev); |
40 | bio_set_dev(bio, bdev); |
41 | bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; |
42 | bio->bi_end_io = end_io; |
43 | |
44 | for (i = 0; i < nr; i++) |
45 | bio_add_page(bio, page + i, PAGE_SIZE, 0); |
46 | VM_BUG_ON(bio->bi_iter.bi_size != PAGE_SIZE * nr); |
47 | } |
48 | return bio; |
49 | } |
50 | |
51 | void end_swap_bio_write(struct bio *bio) |
52 | { |
53 | struct page *page = bio_first_page_all(bio); |
54 | |
55 | if (bio->bi_status) { |
56 | SetPageError(page); |
57 | /* |
58 | * We failed to write the page out to swap-space. |
59 | * Re-dirty the page in order to avoid it being reclaimed. |
60 | * Also print a dire warning that things will go BAD (tm) |
61 | * very quickly. |
62 | * |
63 | * Also clear PG_reclaim to avoid rotate_reclaimable_page() |
64 | */ |
65 | set_page_dirty(page); |
66 | pr_alert("Write-error on swap-device (%u:%u:%llu)\n" , |
67 | MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)), |
68 | (unsigned long long)bio->bi_iter.bi_sector); |
69 | ClearPageReclaim(page); |
70 | } |
71 | end_page_writeback(page); |
72 | bio_put(bio); |
73 | } |
74 | |
75 | static void swap_slot_free_notify(struct page *page) |
76 | { |
77 | struct swap_info_struct *sis; |
78 | struct gendisk *disk; |
79 | |
80 | /* |
81 | * There is no guarantee that the page is in swap cache - the software |
82 | * suspend code (at least) uses end_swap_bio_read() against a non- |
83 | * swapcache page. So we must check PG_swapcache before proceeding with |
84 | * this optimization. |
85 | */ |
86 | if (unlikely(!PageSwapCache(page))) |
87 | return; |
88 | |
89 | sis = page_swap_info(page); |
90 | if (!(sis->flags & SWP_BLKDEV)) |
91 | return; |
92 | |
93 | /* |
94 | * The swap subsystem performs lazy swap slot freeing, |
95 | * expecting that the page will be swapped out again. |
96 | * So we can avoid an unnecessary write if the page |
97 | * isn't redirtied. |
98 | * This is good for real swap storage because we can |
99 | * reduce unnecessary I/O and enhance wear-leveling |
100 | * if an SSD is used as the as swap device. |
101 | * But if in-memory swap device (eg zram) is used, |
102 | * this causes a duplicated copy between uncompressed |
103 | * data in VM-owned memory and compressed data in |
104 | * zram-owned memory. So let's free zram-owned memory |
105 | * and make the VM-owned decompressed page *dirty*, |
106 | * so the page should be swapped out somewhere again if |
107 | * we again wish to reclaim it. |
108 | */ |
109 | disk = sis->bdev->bd_disk; |
110 | if (disk->fops->swap_slot_free_notify) { |
111 | swp_entry_t entry; |
112 | unsigned long offset; |
113 | |
114 | entry.val = page_private(page); |
115 | offset = swp_offset(entry); |
116 | |
117 | SetPageDirty(page); |
118 | disk->fops->swap_slot_free_notify(sis->bdev, |
119 | offset); |
120 | } |
121 | } |
122 | |
123 | static void end_swap_bio_read(struct bio *bio) |
124 | { |
125 | struct page *page = bio_first_page_all(bio); |
126 | struct task_struct *waiter = bio->bi_private; |
127 | |
128 | if (bio->bi_status) { |
129 | SetPageError(page); |
130 | ClearPageUptodate(page); |
131 | pr_alert("Read-error on swap-device (%u:%u:%llu)\n" , |
132 | MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)), |
133 | (unsigned long long)bio->bi_iter.bi_sector); |
134 | goto out; |
135 | } |
136 | |
137 | SetPageUptodate(page); |
138 | swap_slot_free_notify(page); |
139 | out: |
140 | unlock_page(page); |
141 | WRITE_ONCE(bio->bi_private, NULL); |
142 | bio_put(bio); |
143 | blk_wake_io_task(waiter); |
144 | put_task_struct(waiter); |
145 | } |
146 | |
147 | int generic_swapfile_activate(struct swap_info_struct *sis, |
148 | struct file *swap_file, |
149 | sector_t *span) |
150 | { |
151 | struct address_space *mapping = swap_file->f_mapping; |
152 | struct inode *inode = mapping->host; |
153 | unsigned blocks_per_page; |
154 | unsigned long page_no; |
155 | unsigned blkbits; |
156 | sector_t probe_block; |
157 | sector_t last_block; |
158 | sector_t lowest_block = -1; |
159 | sector_t highest_block = 0; |
160 | int nr_extents = 0; |
161 | int ret; |
162 | |
163 | blkbits = inode->i_blkbits; |
164 | blocks_per_page = PAGE_SIZE >> blkbits; |
165 | |
166 | /* |
167 | * Map all the blocks into the extent list. This code doesn't try |
168 | * to be very smart. |
169 | */ |
170 | probe_block = 0; |
171 | page_no = 0; |
172 | last_block = i_size_read(inode) >> blkbits; |
173 | while ((probe_block + blocks_per_page) <= last_block && |
174 | page_no < sis->max) { |
175 | unsigned block_in_page; |
176 | sector_t first_block; |
177 | |
178 | cond_resched(); |
179 | |
180 | first_block = bmap(inode, probe_block); |
181 | if (first_block == 0) |
182 | goto bad_bmap; |
183 | |
184 | /* |
185 | * It must be PAGE_SIZE aligned on-disk |
186 | */ |
187 | if (first_block & (blocks_per_page - 1)) { |
188 | probe_block++; |
189 | goto reprobe; |
190 | } |
191 | |
192 | for (block_in_page = 1; block_in_page < blocks_per_page; |
193 | block_in_page++) { |
194 | sector_t block; |
195 | |
196 | block = bmap(inode, probe_block + block_in_page); |
197 | if (block == 0) |
198 | goto bad_bmap; |
199 | if (block != first_block + block_in_page) { |
200 | /* Discontiguity */ |
201 | probe_block++; |
202 | goto reprobe; |
203 | } |
204 | } |
205 | |
206 | first_block >>= (PAGE_SHIFT - blkbits); |
207 | if (page_no) { /* exclude the header page */ |
208 | if (first_block < lowest_block) |
209 | lowest_block = first_block; |
210 | if (first_block > highest_block) |
211 | highest_block = first_block; |
212 | } |
213 | |
214 | /* |
215 | * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks |
216 | */ |
217 | ret = add_swap_extent(sis, page_no, 1, first_block); |
218 | if (ret < 0) |
219 | goto out; |
220 | nr_extents += ret; |
221 | page_no++; |
222 | probe_block += blocks_per_page; |
223 | reprobe: |
224 | continue; |
225 | } |
226 | ret = nr_extents; |
227 | *span = 1 + highest_block - lowest_block; |
228 | if (page_no == 0) |
229 | page_no = 1; /* force Empty message */ |
230 | sis->max = page_no; |
231 | sis->pages = page_no - 1; |
232 | sis->highest_bit = page_no - 1; |
233 | out: |
234 | return ret; |
235 | bad_bmap: |
236 | pr_err("swapon: swapfile has holes\n" ); |
237 | ret = -EINVAL; |
238 | goto out; |
239 | } |
240 | |
241 | /* |
242 | * We may have stale swap cache pages in memory: notice |
243 | * them here and get rid of the unnecessary final write. |
244 | */ |
245 | int swap_writepage(struct page *page, struct writeback_control *wbc) |
246 | { |
247 | int ret = 0; |
248 | |
249 | if (try_to_free_swap(page)) { |
250 | unlock_page(page); |
251 | goto out; |
252 | } |
253 | if (frontswap_store(page) == 0) { |
254 | set_page_writeback(page); |
255 | unlock_page(page); |
256 | end_page_writeback(page); |
257 | goto out; |
258 | } |
259 | ret = __swap_writepage(page, wbc, end_swap_bio_write); |
260 | out: |
261 | return ret; |
262 | } |
263 | |
264 | static sector_t swap_page_sector(struct page *page) |
265 | { |
266 | return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9); |
267 | } |
268 | |
269 | static inline void count_swpout_vm_event(struct page *page) |
270 | { |
271 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
272 | if (unlikely(PageTransHuge(page))) |
273 | count_vm_event(THP_SWPOUT); |
274 | #endif |
275 | count_vm_events(PSWPOUT, hpage_nr_pages(page)); |
276 | } |
277 | |
278 | int __swap_writepage(struct page *page, struct writeback_control *wbc, |
279 | bio_end_io_t end_write_func) |
280 | { |
281 | struct bio *bio; |
282 | int ret; |
283 | struct swap_info_struct *sis = page_swap_info(page); |
284 | |
285 | VM_BUG_ON_PAGE(!PageSwapCache(page), page); |
286 | if (sis->flags & SWP_FS) { |
287 | struct kiocb kiocb; |
288 | struct file *swap_file = sis->swap_file; |
289 | struct address_space *mapping = swap_file->f_mapping; |
290 | struct bio_vec bv = { |
291 | .bv_page = page, |
292 | .bv_len = PAGE_SIZE, |
293 | .bv_offset = 0 |
294 | }; |
295 | struct iov_iter from; |
296 | |
297 | iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE); |
298 | init_sync_kiocb(&kiocb, swap_file); |
299 | kiocb.ki_pos = page_file_offset(page); |
300 | |
301 | set_page_writeback(page); |
302 | unlock_page(page); |
303 | ret = mapping->a_ops->direct_IO(&kiocb, &from); |
304 | if (ret == PAGE_SIZE) { |
305 | count_vm_event(PSWPOUT); |
306 | ret = 0; |
307 | } else { |
308 | /* |
309 | * In the case of swap-over-nfs, this can be a |
310 | * temporary failure if the system has limited |
311 | * memory for allocating transmit buffers. |
312 | * Mark the page dirty and avoid |
313 | * rotate_reclaimable_page but rate-limit the |
314 | * messages but do not flag PageError like |
315 | * the normal direct-to-bio case as it could |
316 | * be temporary. |
317 | */ |
318 | set_page_dirty(page); |
319 | ClearPageReclaim(page); |
320 | pr_err_ratelimited("Write error on dio swapfile (%llu)\n" , |
321 | page_file_offset(page)); |
322 | } |
323 | end_page_writeback(page); |
324 | return ret; |
325 | } |
326 | |
327 | ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); |
328 | if (!ret) { |
329 | count_swpout_vm_event(page); |
330 | return 0; |
331 | } |
332 | |
333 | ret = 0; |
334 | bio = get_swap_bio(GFP_NOIO, page, end_write_func); |
335 | if (bio == NULL) { |
336 | set_page_dirty(page); |
337 | unlock_page(page); |
338 | ret = -ENOMEM; |
339 | goto out; |
340 | } |
341 | bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc); |
342 | bio_associate_blkg_from_page(bio, page); |
343 | count_swpout_vm_event(page); |
344 | set_page_writeback(page); |
345 | unlock_page(page); |
346 | submit_bio(bio); |
347 | out: |
348 | return ret; |
349 | } |
350 | |
351 | int swap_readpage(struct page *page, bool synchronous) |
352 | { |
353 | struct bio *bio; |
354 | int ret = 0; |
355 | struct swap_info_struct *sis = page_swap_info(page); |
356 | blk_qc_t qc; |
357 | struct gendisk *disk; |
358 | |
359 | VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page); |
360 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
361 | VM_BUG_ON_PAGE(PageUptodate(page), page); |
362 | if (frontswap_load(page) == 0) { |
363 | SetPageUptodate(page); |
364 | unlock_page(page); |
365 | goto out; |
366 | } |
367 | |
368 | if (sis->flags & SWP_FS) { |
369 | struct file *swap_file = sis->swap_file; |
370 | struct address_space *mapping = swap_file->f_mapping; |
371 | |
372 | ret = mapping->a_ops->readpage(swap_file, page); |
373 | if (!ret) |
374 | count_vm_event(PSWPIN); |
375 | return ret; |
376 | } |
377 | |
378 | ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); |
379 | if (!ret) { |
380 | if (trylock_page(page)) { |
381 | swap_slot_free_notify(page); |
382 | unlock_page(page); |
383 | } |
384 | |
385 | count_vm_event(PSWPIN); |
386 | return 0; |
387 | } |
388 | |
389 | ret = 0; |
390 | bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); |
391 | if (bio == NULL) { |
392 | unlock_page(page); |
393 | ret = -ENOMEM; |
394 | goto out; |
395 | } |
396 | disk = bio->bi_disk; |
397 | /* |
398 | * Keep this task valid during swap readpage because the oom killer may |
399 | * attempt to access it in the page fault retry time check. |
400 | */ |
401 | get_task_struct(current); |
402 | bio->bi_private = current; |
403 | bio_set_op_attrs(bio, REQ_OP_READ, 0); |
404 | if (synchronous) |
405 | bio->bi_opf |= REQ_HIPRI; |
406 | count_vm_event(PSWPIN); |
407 | bio_get(bio); |
408 | qc = submit_bio(bio); |
409 | while (synchronous) { |
410 | set_current_state(TASK_UNINTERRUPTIBLE); |
411 | if (!READ_ONCE(bio->bi_private)) |
412 | break; |
413 | |
414 | if (!blk_poll(disk->queue, qc, true)) |
415 | io_schedule(); |
416 | } |
417 | __set_current_state(TASK_RUNNING); |
418 | bio_put(bio); |
419 | |
420 | out: |
421 | return ret; |
422 | } |
423 | |
424 | int swap_set_page_dirty(struct page *page) |
425 | { |
426 | struct swap_info_struct *sis = page_swap_info(page); |
427 | |
428 | if (sis->flags & SWP_FS) { |
429 | struct address_space *mapping = sis->swap_file->f_mapping; |
430 | |
431 | VM_BUG_ON_PAGE(!PageSwapCache(page), page); |
432 | return mapping->a_ops->set_page_dirty(page); |
433 | } else { |
434 | return __set_page_dirty_no_writeback(page); |
435 | } |
436 | } |
437 | |