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path: root/mm/page_io.c (plain)
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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 cond_resched();
170
171 first_block = bmap(inode, probe_block);
172 if (first_block == 0)
173 goto bad_bmap;
174
175 /*
176 * It must be PAGE_SIZE aligned on-disk
177 */
178 if (first_block & (blocks_per_page - 1)) {
179 probe_block++;
180 goto reprobe;
181 }
182
183 for (block_in_page = 1; block_in_page < blocks_per_page;
184 block_in_page++) {
185 sector_t block;
186
187 block = bmap(inode, probe_block + block_in_page);
188 if (block == 0)
189 goto bad_bmap;
190 if (block != first_block + block_in_page) {
191 /* Discontiguity */
192 probe_block++;
193 goto reprobe;
194 }
195 }
196
197 first_block >>= (PAGE_SHIFT - blkbits);
198 if (page_no) { /* exclude the header page */
199 if (first_block < lowest_block)
200 lowest_block = first_block;
201 if (first_block > highest_block)
202 highest_block = first_block;
203 }
204
205 /*
206 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
207 */
208 ret = add_swap_extent(sis, page_no, 1, first_block);
209 if (ret < 0)
210 goto out;
211 nr_extents += ret;
212 page_no++;
213 probe_block += blocks_per_page;
214reprobe:
215 continue;
216 }
217 ret = nr_extents;
218 *span = 1 + highest_block - lowest_block;
219 if (page_no == 0)
220 page_no = 1; /* force Empty message */
221 sis->max = page_no;
222 sis->pages = page_no - 1;
223 sis->highest_bit = page_no - 1;
224out:
225 return ret;
226bad_bmap:
227 pr_err("swapon: swapfile has holes\n");
228 ret = -EINVAL;
229 goto out;
230}
231
232/*
233 * We may have stale swap cache pages in memory: notice
234 * them here and get rid of the unnecessary final write.
235 */
236int swap_writepage(struct page *page, struct writeback_control *wbc)
237{
238 int ret = 0;
239
240 if (try_to_free_swap(page)) {
241 unlock_page(page);
242 goto out;
243 }
244 if (frontswap_store(page) == 0) {
245 set_page_writeback(page);
246 unlock_page(page);
247 end_page_writeback(page);
248 goto out;
249 }
250 ret = __swap_writepage(page, wbc, end_swap_bio_write);
251out:
252 return ret;
253}
254
255static sector_t swap_page_sector(struct page *page)
256{
257 return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
258}
259
260int __swap_writepage(struct page *page, struct writeback_control *wbc,
261 bio_end_io_t end_write_func)
262{
263 struct bio *bio;
264 int ret;
265 struct swap_info_struct *sis = page_swap_info(page);
266
267 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
268 if (sis->flags & SWP_FILE) {
269 struct kiocb kiocb;
270 struct file *swap_file = sis->swap_file;
271 struct address_space *mapping = swap_file->f_mapping;
272 struct bio_vec bv = {
273 .bv_page = page,
274 .bv_len = PAGE_SIZE,
275 .bv_offset = 0
276 };
277 struct iov_iter from;
278
279 iov_iter_bvec(&from, ITER_BVEC | WRITE, &bv, 1, PAGE_SIZE);
280 init_sync_kiocb(&kiocb, swap_file);
281 kiocb.ki_pos = page_file_offset(page);
282
283 set_page_writeback(page);
284 unlock_page(page);
285 ret = mapping->a_ops->direct_IO(&kiocb, &from);
286 if (ret == PAGE_SIZE) {
287 count_vm_event(PSWPOUT);
288 ret = 0;
289 } else {
290 /*
291 * In the case of swap-over-nfs, this can be a
292 * temporary failure if the system has limited
293 * memory for allocating transmit buffers.
294 * Mark the page dirty and avoid
295 * rotate_reclaimable_page but rate-limit the
296 * messages but do not flag PageError like
297 * the normal direct-to-bio case as it could
298 * be temporary.
299 */
300 set_page_dirty(page);
301 ClearPageReclaim(page);
302 pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
303 page_file_offset(page));
304 }
305 end_page_writeback(page);
306 return ret;
307 }
308
309 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
310 if (!ret) {
311 count_vm_event(PSWPOUT);
312 return 0;
313 }
314
315 ret = 0;
316 bio = get_swap_bio(GFP_NOIO, page, end_write_func);
317 if (bio == NULL) {
318 set_page_dirty(page);
319 unlock_page(page);
320 ret = -ENOMEM;
321 goto out;
322 }
323 if (wbc->sync_mode == WB_SYNC_ALL)
324 bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC);
325 else
326 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
327 count_vm_event(PSWPOUT);
328 set_page_writeback(page);
329 unlock_page(page);
330 submit_bio(bio);
331out:
332 return ret;
333}
334
335int swap_readpage(struct page *page)
336{
337 struct bio *bio;
338 int ret = 0;
339 struct swap_info_struct *sis = page_swap_info(page);
340
341 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
342 VM_BUG_ON_PAGE(!PageLocked(page), page);
343 VM_BUG_ON_PAGE(PageUptodate(page), page);
344 if (frontswap_load(page) == 0) {
345 SetPageUptodate(page);
346 unlock_page(page);
347 goto out;
348 }
349
350 if (sis->flags & SWP_FILE) {
351 struct file *swap_file = sis->swap_file;
352 struct address_space *mapping = swap_file->f_mapping;
353
354 ret = mapping->a_ops->readpage(swap_file, page);
355 if (!ret)
356 count_vm_event(PSWPIN);
357 return ret;
358 }
359
360 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
361 if (!ret) {
362 if (trylock_page(page)) {
363 swap_slot_free_notify(page);
364 unlock_page(page);
365 }
366
367 count_vm_event(PSWPIN);
368 return 0;
369 }
370
371 ret = 0;
372 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
373 if (bio == NULL) {
374 unlock_page(page);
375 ret = -ENOMEM;
376 goto out;
377 }
378 bio_set_op_attrs(bio, REQ_OP_READ, 0);
379 count_vm_event(PSWPIN);
380 submit_bio(bio);
381out:
382 return ret;
383}
384
385int swap_set_page_dirty(struct page *page)
386{
387 struct swap_info_struct *sis = page_swap_info(page);
388
389 if (sis->flags & SWP_FILE) {
390 struct address_space *mapping = sis->swap_file->f_mapping;
391
392 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
393 return mapping->a_ops->set_page_dirty(page);
394 } else {
395 return __set_page_dirty_no_writeback(page);
396 }
397}
398
generated by cgit at 2024-05-18 15:44:05 (GMT)