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