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