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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->bi_io_vec[0].bv_page; | |
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->bi_io_vec[0].bv_page; | |
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 | wake_up_process(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_FILE) { | |
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, ITER_BVEC | 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 | wbc_to_write_flags(wbc); | |
342 | count_swpout_vm_event(page); | |
343 | set_page_writeback(page); | |
344 | unlock_page(page); | |
345 | submit_bio(bio); | |
346 | out: | |
347 | return ret; | |
348 | } | |
349 | ||
350 | int swap_readpage(struct page *page, bool synchronous) | |
351 | { | |
352 | struct bio *bio; | |
353 | int ret = 0; | |
354 | struct swap_info_struct *sis = page_swap_info(page); | |
355 | blk_qc_t qc; | |
356 | struct gendisk *disk; | |
357 | ||
358 | VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page); | |
359 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
360 | VM_BUG_ON_PAGE(PageUptodate(page), page); | |
361 | if (frontswap_load(page) == 0) { | |
362 | SetPageUptodate(page); | |
363 | unlock_page(page); | |
364 | goto out; | |
365 | } | |
366 | ||
367 | if (sis->flags & SWP_FILE) { | |
368 | struct file *swap_file = sis->swap_file; | |
369 | struct address_space *mapping = swap_file->f_mapping; | |
370 | ||
371 | ret = mapping->a_ops->readpage(swap_file, page); | |
372 | if (!ret) | |
373 | count_vm_event(PSWPIN); | |
374 | return ret; | |
375 | } | |
376 | ||
377 | ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); | |
378 | if (!ret) { | |
379 | if (trylock_page(page)) { | |
380 | swap_slot_free_notify(page); | |
381 | unlock_page(page); | |
382 | } | |
383 | ||
384 | count_vm_event(PSWPIN); | |
385 | return 0; | |
386 | } | |
387 | ||
388 | ret = 0; | |
389 | bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); | |
390 | if (bio == NULL) { | |
391 | unlock_page(page); | |
392 | ret = -ENOMEM; | |
393 | goto out; | |
394 | } | |
395 | disk = bio->bi_disk; | |
396 | /* | |
397 | * Keep this task valid during swap readpage because the oom killer may | |
398 | * attempt to access it in the page fault retry time check. | |
399 | */ | |
400 | get_task_struct(current); | |
401 | bio->bi_private = current; | |
402 | bio_set_op_attrs(bio, REQ_OP_READ, 0); | |
403 | count_vm_event(PSWPIN); | |
404 | bio_get(bio); | |
405 | qc = submit_bio(bio); | |
406 | while (synchronous) { | |
407 | set_current_state(TASK_UNINTERRUPTIBLE); | |
408 | if (!READ_ONCE(bio->bi_private)) | |
409 | break; | |
410 | ||
411 | if (!blk_poll(disk->queue, qc)) | |
412 | break; | |
413 | } | |
414 | __set_current_state(TASK_RUNNING); | |
415 | bio_put(bio); | |
416 | ||
417 | out: | |
418 | return ret; | |
419 | } | |
420 | ||
421 | int swap_set_page_dirty(struct page *page) | |
422 | { | |
423 | struct swap_info_struct *sis = page_swap_info(page); | |
424 | ||
425 | if (sis->flags & SWP_FILE) { | |
426 | struct address_space *mapping = sis->swap_file->f_mapping; | |
427 | ||
428 | VM_BUG_ON_PAGE(!PageSwapCache(page), page); | |
429 | return mapping->a_ops->set_page_dirty(page); | |
430 | } else { | |
431 | return __set_page_dirty_no_writeback(page); | |
432 | } | |
433 | } |