1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2010 Red Hat, Inc.
4 * Copyright (C) 2016-2023 Christoph Hellwig.
5 */
6 #include <linux/module.h>
7 #include <linux/compiler.h>
8 #include <linux/fs.h>
9 #include <linux/iomap.h>
10 #include <linux/pagemap.h>
11 #include <linux/uio.h>
12 #include <linux/buffer_head.h>
13 #include <linux/dax.h>
14 #include <linux/writeback.h>
15 #include <linux/swap.h>
16 #include <linux/bio.h>
17 #include <linux/sched/signal.h>
18 #include <linux/migrate.h>
19 #include "internal.h"
20 #include "trace.h"
21
22 #include "../internal.h"
23
24 /*
25 * Structure allocated for each folio to track per-block uptodate, dirty state
26 * and I/O completions.
27 */
28 struct iomap_folio_state {
29 spinlock_t state_lock;
30 unsigned int read_bytes_pending;
31 atomic_t write_bytes_pending;
32
33 /*
34 * Each block has two bits in this bitmap:
35 * Bits [0..blocks_per_folio) has the uptodate status.
36 * Bits [b_p_f...(2*b_p_f)) has the dirty status.
37 */
38 unsigned long state[];
39 };
40
ifs_is_fully_uptodate(struct folio * folio,struct iomap_folio_state * ifs)41 static inline bool ifs_is_fully_uptodate(struct folio *folio,
42 struct iomap_folio_state *ifs)
43 {
44 struct inode *inode = folio->mapping->host;
45
46 return bitmap_full(ifs->state, i_blocks_per_folio(inode, folio));
47 }
48
ifs_block_is_uptodate(struct iomap_folio_state * ifs,unsigned int block)49 static inline bool ifs_block_is_uptodate(struct iomap_folio_state *ifs,
50 unsigned int block)
51 {
52 return test_bit(block, ifs->state);
53 }
54
ifs_set_range_uptodate(struct folio * folio,struct iomap_folio_state * ifs,size_t off,size_t len)55 static bool ifs_set_range_uptodate(struct folio *folio,
56 struct iomap_folio_state *ifs, size_t off, size_t len)
57 {
58 struct inode *inode = folio->mapping->host;
59 unsigned int first_blk = off >> inode->i_blkbits;
60 unsigned int last_blk = (off + len - 1) >> inode->i_blkbits;
61 unsigned int nr_blks = last_blk - first_blk + 1;
62
63 bitmap_set(ifs->state, first_blk, nr_blks);
64 return ifs_is_fully_uptodate(folio, ifs);
65 }
66
iomap_set_range_uptodate(struct folio * folio,size_t off,size_t len)67 static void iomap_set_range_uptodate(struct folio *folio, size_t off,
68 size_t len)
69 {
70 struct iomap_folio_state *ifs = folio->private;
71 unsigned long flags;
72 bool uptodate = true;
73
74 if (folio_test_uptodate(folio))
75 return;
76
77 if (ifs) {
78 spin_lock_irqsave(&ifs->state_lock, flags);
79 uptodate = ifs_set_range_uptodate(folio, ifs, off, len);
80 spin_unlock_irqrestore(&ifs->state_lock, flags);
81 }
82
83 if (uptodate)
84 folio_mark_uptodate(folio);
85 }
86
ifs_block_is_dirty(struct folio * folio,struct iomap_folio_state * ifs,int block)87 static inline bool ifs_block_is_dirty(struct folio *folio,
88 struct iomap_folio_state *ifs, int block)
89 {
90 struct inode *inode = folio->mapping->host;
91 unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
92
93 return test_bit(block + blks_per_folio, ifs->state);
94 }
95
ifs_find_dirty_range(struct folio * folio,struct iomap_folio_state * ifs,u64 * range_start,u64 range_end)96 static unsigned ifs_find_dirty_range(struct folio *folio,
97 struct iomap_folio_state *ifs, u64 *range_start, u64 range_end)
98 {
99 struct inode *inode = folio->mapping->host;
100 unsigned start_blk =
101 offset_in_folio(folio, *range_start) >> inode->i_blkbits;
102 unsigned end_blk = min_not_zero(
103 offset_in_folio(folio, range_end) >> inode->i_blkbits,
104 i_blocks_per_folio(inode, folio));
105 unsigned nblks = 1;
106
107 while (!ifs_block_is_dirty(folio, ifs, start_blk))
108 if (++start_blk == end_blk)
109 return 0;
110
111 while (start_blk + nblks < end_blk) {
112 if (!ifs_block_is_dirty(folio, ifs, start_blk + nblks))
113 break;
114 nblks++;
115 }
116
117 *range_start = folio_pos(folio) + (start_blk << inode->i_blkbits);
118 return nblks << inode->i_blkbits;
119 }
120
iomap_find_dirty_range(struct folio * folio,u64 * range_start,u64 range_end)121 static unsigned iomap_find_dirty_range(struct folio *folio, u64 *range_start,
122 u64 range_end)
123 {
124 struct iomap_folio_state *ifs = folio->private;
125
126 if (*range_start >= range_end)
127 return 0;
128
129 if (ifs)
130 return ifs_find_dirty_range(folio, ifs, range_start, range_end);
131 return range_end - *range_start;
132 }
133
ifs_clear_range_dirty(struct folio * folio,struct iomap_folio_state * ifs,size_t off,size_t len)134 static void ifs_clear_range_dirty(struct folio *folio,
135 struct iomap_folio_state *ifs, size_t off, size_t len)
136 {
137 struct inode *inode = folio->mapping->host;
138 unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
139 unsigned int first_blk = (off >> inode->i_blkbits);
140 unsigned int last_blk = (off + len - 1) >> inode->i_blkbits;
141 unsigned int nr_blks = last_blk - first_blk + 1;
142 unsigned long flags;
143
144 spin_lock_irqsave(&ifs->state_lock, flags);
145 bitmap_clear(ifs->state, first_blk + blks_per_folio, nr_blks);
146 spin_unlock_irqrestore(&ifs->state_lock, flags);
147 }
148
iomap_clear_range_dirty(struct folio * folio,size_t off,size_t len)149 static void iomap_clear_range_dirty(struct folio *folio, size_t off, size_t len)
150 {
151 struct iomap_folio_state *ifs = folio->private;
152
153 if (ifs)
154 ifs_clear_range_dirty(folio, ifs, off, len);
155 }
156
ifs_set_range_dirty(struct folio * folio,struct iomap_folio_state * ifs,size_t off,size_t len)157 static void ifs_set_range_dirty(struct folio *folio,
158 struct iomap_folio_state *ifs, size_t off, size_t len)
159 {
160 struct inode *inode = folio->mapping->host;
161 unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
162 unsigned int first_blk = (off >> inode->i_blkbits);
163 unsigned int last_blk = (off + len - 1) >> inode->i_blkbits;
164 unsigned int nr_blks = last_blk - first_blk + 1;
165 unsigned long flags;
166
167 spin_lock_irqsave(&ifs->state_lock, flags);
168 bitmap_set(ifs->state, first_blk + blks_per_folio, nr_blks);
169 spin_unlock_irqrestore(&ifs->state_lock, flags);
170 }
171
iomap_set_range_dirty(struct folio * folio,size_t off,size_t len)172 static void iomap_set_range_dirty(struct folio *folio, size_t off, size_t len)
173 {
174 struct iomap_folio_state *ifs = folio->private;
175
176 if (ifs)
177 ifs_set_range_dirty(folio, ifs, off, len);
178 }
179
ifs_alloc(struct inode * inode,struct folio * folio,unsigned int flags)180 static struct iomap_folio_state *ifs_alloc(struct inode *inode,
181 struct folio *folio, unsigned int flags)
182 {
183 struct iomap_folio_state *ifs = folio->private;
184 unsigned int nr_blocks = i_blocks_per_folio(inode, folio);
185 gfp_t gfp;
186
187 if (ifs || nr_blocks <= 1)
188 return ifs;
189
190 if (flags & IOMAP_NOWAIT)
191 gfp = GFP_NOWAIT;
192 else
193 gfp = GFP_NOFS | __GFP_NOFAIL;
194
195 /*
196 * ifs->state tracks two sets of state flags when the
197 * filesystem block size is smaller than the folio size.
198 * The first state tracks per-block uptodate and the
199 * second tracks per-block dirty state.
200 */
201 ifs = kzalloc(struct_size(ifs, state,
202 BITS_TO_LONGS(2 * nr_blocks)), gfp);
203 if (!ifs)
204 return ifs;
205
206 spin_lock_init(&ifs->state_lock);
207 if (folio_test_uptodate(folio))
208 bitmap_set(ifs->state, 0, nr_blocks);
209 if (folio_test_dirty(folio))
210 bitmap_set(ifs->state, nr_blocks, nr_blocks);
211 folio_attach_private(folio, ifs);
212
213 return ifs;
214 }
215
ifs_free(struct folio * folio)216 static void ifs_free(struct folio *folio)
217 {
218 struct iomap_folio_state *ifs = folio_detach_private(folio);
219
220 if (!ifs)
221 return;
222 WARN_ON_ONCE(ifs->read_bytes_pending != 0);
223 WARN_ON_ONCE(atomic_read(&ifs->write_bytes_pending));
224 WARN_ON_ONCE(ifs_is_fully_uptodate(folio, ifs) !=
225 folio_test_uptodate(folio));
226 kfree(ifs);
227 }
228
229 /*
230 * Calculate the range inside the folio that we actually need to read.
231 */
iomap_adjust_read_range(struct inode * inode,struct folio * folio,loff_t * pos,loff_t length,size_t * offp,size_t * lenp)232 static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
233 loff_t *pos, loff_t length, size_t *offp, size_t *lenp)
234 {
235 struct iomap_folio_state *ifs = folio->private;
236 loff_t orig_pos = *pos;
237 loff_t isize = i_size_read(inode);
238 unsigned block_bits = inode->i_blkbits;
239 unsigned block_size = (1 << block_bits);
240 size_t poff = offset_in_folio(folio, *pos);
241 size_t plen = min_t(loff_t, folio_size(folio) - poff, length);
242 size_t orig_plen = plen;
243 unsigned first = poff >> block_bits;
244 unsigned last = (poff + plen - 1) >> block_bits;
245
246 /*
247 * If the block size is smaller than the page size, we need to check the
248 * per-block uptodate status and adjust the offset and length if needed
249 * to avoid reading in already uptodate ranges.
250 */
251 if (ifs) {
252 unsigned int i;
253
254 /* move forward for each leading block marked uptodate */
255 for (i = first; i <= last; i++) {
256 if (!ifs_block_is_uptodate(ifs, i))
257 break;
258 *pos += block_size;
259 poff += block_size;
260 plen -= block_size;
261 first++;
262 }
263
264 /* truncate len if we find any trailing uptodate block(s) */
265 while (++i <= last) {
266 if (ifs_block_is_uptodate(ifs, i)) {
267 plen -= (last - i + 1) * block_size;
268 last = i - 1;
269 break;
270 }
271 }
272 }
273
274 /*
275 * If the extent spans the block that contains the i_size, we need to
276 * handle both halves separately so that we properly zero data in the
277 * page cache for blocks that are entirely outside of i_size.
278 */
279 if (orig_pos <= isize && orig_pos + orig_plen > isize) {
280 unsigned end = offset_in_folio(folio, isize - 1) >> block_bits;
281
282 if (first <= end && last > end)
283 plen -= (last - end) * block_size;
284 }
285
286 *offp = poff;
287 *lenp = plen;
288 }
289
iomap_finish_folio_read(struct folio * folio,size_t off,size_t len,int error)290 static void iomap_finish_folio_read(struct folio *folio, size_t off,
291 size_t len, int error)
292 {
293 struct iomap_folio_state *ifs = folio->private;
294 bool uptodate = !error;
295 bool finished = true;
296
297 if (ifs) {
298 unsigned long flags;
299
300 spin_lock_irqsave(&ifs->state_lock, flags);
301 if (!error)
302 uptodate = ifs_set_range_uptodate(folio, ifs, off, len);
303 ifs->read_bytes_pending -= len;
304 finished = !ifs->read_bytes_pending;
305 spin_unlock_irqrestore(&ifs->state_lock, flags);
306 }
307
308 if (finished)
309 folio_end_read(folio, uptodate);
310 }
311
iomap_read_end_io(struct bio * bio)312 static void iomap_read_end_io(struct bio *bio)
313 {
314 int error = blk_status_to_errno(bio->bi_status);
315 struct folio_iter fi;
316
317 bio_for_each_folio_all(fi, bio)
318 iomap_finish_folio_read(fi.folio, fi.offset, fi.length, error);
319 bio_put(bio);
320 }
321
322 struct iomap_readpage_ctx {
323 struct folio *cur_folio;
324 bool cur_folio_in_bio;
325 struct bio *bio;
326 struct readahead_control *rac;
327 };
328
329 /**
330 * iomap_read_inline_data - copy inline data into the page cache
331 * @iter: iteration structure
332 * @folio: folio to copy to
333 *
334 * Copy the inline data in @iter into @folio and zero out the rest of the folio.
335 * Only a single IOMAP_INLINE extent is allowed at the end of each file.
336 * Returns zero for success to complete the read, or the usual negative errno.
337 */
iomap_read_inline_data(const struct iomap_iter * iter,struct folio * folio)338 static int iomap_read_inline_data(const struct iomap_iter *iter,
339 struct folio *folio)
340 {
341 const struct iomap *iomap = iomap_iter_srcmap(iter);
342 size_t size = i_size_read(iter->inode) - iomap->offset;
343 size_t offset = offset_in_folio(folio, iomap->offset);
344
345 if (folio_test_uptodate(folio))
346 return 0;
347
348 if (WARN_ON_ONCE(size > iomap->length))
349 return -EIO;
350 if (offset > 0)
351 ifs_alloc(iter->inode, folio, iter->flags);
352
353 folio_fill_tail(folio, offset, iomap->inline_data, size);
354 iomap_set_range_uptodate(folio, offset, folio_size(folio) - offset);
355 return 0;
356 }
357
iomap_block_needs_zeroing(const struct iomap_iter * iter,loff_t pos)358 static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
359 loff_t pos)
360 {
361 const struct iomap *srcmap = iomap_iter_srcmap(iter);
362
363 return srcmap->type != IOMAP_MAPPED ||
364 (srcmap->flags & IOMAP_F_NEW) ||
365 pos >= i_size_read(iter->inode);
366 }
367
iomap_readpage_iter(struct iomap_iter * iter,struct iomap_readpage_ctx * ctx)368 static int iomap_readpage_iter(struct iomap_iter *iter,
369 struct iomap_readpage_ctx *ctx)
370 {
371 const struct iomap *iomap = &iter->iomap;
372 loff_t pos = iter->pos;
373 loff_t length = iomap_length(iter);
374 struct folio *folio = ctx->cur_folio;
375 struct iomap_folio_state *ifs;
376 size_t poff, plen;
377 sector_t sector;
378 int ret;
379
380 if (iomap->type == IOMAP_INLINE) {
381 ret = iomap_read_inline_data(iter, folio);
382 if (ret)
383 return ret;
384 return iomap_iter_advance(iter, &length);
385 }
386
387 /* zero post-eof blocks as the page may be mapped */
388 ifs = ifs_alloc(iter->inode, folio, iter->flags);
389 iomap_adjust_read_range(iter->inode, folio, &pos, length, &poff, &plen);
390 if (plen == 0)
391 goto done;
392
393 if (iomap_block_needs_zeroing(iter, pos)) {
394 folio_zero_range(folio, poff, plen);
395 iomap_set_range_uptodate(folio, poff, plen);
396 goto done;
397 }
398
399 ctx->cur_folio_in_bio = true;
400 if (ifs) {
401 spin_lock_irq(&ifs->state_lock);
402 ifs->read_bytes_pending += plen;
403 spin_unlock_irq(&ifs->state_lock);
404 }
405
406 sector = iomap_sector(iomap, pos);
407 if (!ctx->bio ||
408 bio_end_sector(ctx->bio) != sector ||
409 !bio_add_folio(ctx->bio, folio, plen, poff)) {
410 gfp_t gfp = mapping_gfp_constraint(folio->mapping, GFP_KERNEL);
411 gfp_t orig_gfp = gfp;
412 unsigned int nr_vecs = DIV_ROUND_UP(length, PAGE_SIZE);
413
414 if (ctx->bio)
415 submit_bio(ctx->bio);
416
417 if (ctx->rac) /* same as readahead_gfp_mask */
418 gfp |= __GFP_NORETRY | __GFP_NOWARN;
419 ctx->bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs),
420 REQ_OP_READ, gfp);
421 /*
422 * If the bio_alloc fails, try it again for a single page to
423 * avoid having to deal with partial page reads. This emulates
424 * what do_mpage_read_folio does.
425 */
426 if (!ctx->bio) {
427 ctx->bio = bio_alloc(iomap->bdev, 1, REQ_OP_READ,
428 orig_gfp);
429 }
430 if (ctx->rac)
431 ctx->bio->bi_opf |= REQ_RAHEAD;
432 ctx->bio->bi_iter.bi_sector = sector;
433 ctx->bio->bi_end_io = iomap_read_end_io;
434 bio_add_folio_nofail(ctx->bio, folio, plen, poff);
435 }
436
437 done:
438 /*
439 * Move the caller beyond our range so that it keeps making progress.
440 * For that, we have to include any leading non-uptodate ranges, but
441 * we can skip trailing ones as they will be handled in the next
442 * iteration.
443 */
444 length = pos - iter->pos + plen;
445 return iomap_iter_advance(iter, &length);
446 }
447
iomap_read_folio_iter(struct iomap_iter * iter,struct iomap_readpage_ctx * ctx)448 static int iomap_read_folio_iter(struct iomap_iter *iter,
449 struct iomap_readpage_ctx *ctx)
450 {
451 int ret;
452
453 while (iomap_length(iter)) {
454 ret = iomap_readpage_iter(iter, ctx);
455 if (ret)
456 return ret;
457 }
458
459 return 0;
460 }
461
iomap_read_folio(struct folio * folio,const struct iomap_ops * ops)462 int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
463 {
464 struct iomap_iter iter = {
465 .inode = folio->mapping->host,
466 .pos = folio_pos(folio),
467 .len = folio_size(folio),
468 };
469 struct iomap_readpage_ctx ctx = {
470 .cur_folio = folio,
471 };
472 int ret;
473
474 trace_iomap_readpage(iter.inode, 1);
475
476 while ((ret = iomap_iter(&iter, ops)) > 0)
477 iter.status = iomap_read_folio_iter(&iter, &ctx);
478
479 if (ctx.bio) {
480 submit_bio(ctx.bio);
481 WARN_ON_ONCE(!ctx.cur_folio_in_bio);
482 } else {
483 WARN_ON_ONCE(ctx.cur_folio_in_bio);
484 folio_unlock(folio);
485 }
486
487 /*
488 * Just like mpage_readahead and block_read_full_folio, we always
489 * return 0 and just set the folio error flag on errors. This
490 * should be cleaned up throughout the stack eventually.
491 */
492 return 0;
493 }
494 EXPORT_SYMBOL_GPL(iomap_read_folio);
495
iomap_readahead_iter(struct iomap_iter * iter,struct iomap_readpage_ctx * ctx)496 static int iomap_readahead_iter(struct iomap_iter *iter,
497 struct iomap_readpage_ctx *ctx)
498 {
499 int ret;
500
501 while (iomap_length(iter)) {
502 if (ctx->cur_folio &&
503 offset_in_folio(ctx->cur_folio, iter->pos) == 0) {
504 if (!ctx->cur_folio_in_bio)
505 folio_unlock(ctx->cur_folio);
506 ctx->cur_folio = NULL;
507 }
508 if (!ctx->cur_folio) {
509 ctx->cur_folio = readahead_folio(ctx->rac);
510 ctx->cur_folio_in_bio = false;
511 }
512 ret = iomap_readpage_iter(iter, ctx);
513 if (ret)
514 return ret;
515 }
516
517 return 0;
518 }
519
520 /**
521 * iomap_readahead - Attempt to read pages from a file.
522 * @rac: Describes the pages to be read.
523 * @ops: The operations vector for the filesystem.
524 *
525 * This function is for filesystems to call to implement their readahead
526 * address_space operation.
527 *
528 * Context: The @ops callbacks may submit I/O (eg to read the addresses of
529 * blocks from disc), and may wait for it. The caller may be trying to
530 * access a different page, and so sleeping excessively should be avoided.
531 * It may allocate memory, but should avoid costly allocations. This
532 * function is called with memalloc_nofs set, so allocations will not cause
533 * the filesystem to be reentered.
534 */
iomap_readahead(struct readahead_control * rac,const struct iomap_ops * ops)535 void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
536 {
537 struct iomap_iter iter = {
538 .inode = rac->mapping->host,
539 .pos = readahead_pos(rac),
540 .len = readahead_length(rac),
541 };
542 struct iomap_readpage_ctx ctx = {
543 .rac = rac,
544 };
545
546 trace_iomap_readahead(rac->mapping->host, readahead_count(rac));
547
548 while (iomap_iter(&iter, ops) > 0)
549 iter.status = iomap_readahead_iter(&iter, &ctx);
550
551 if (ctx.bio)
552 submit_bio(ctx.bio);
553 if (ctx.cur_folio) {
554 if (!ctx.cur_folio_in_bio)
555 folio_unlock(ctx.cur_folio);
556 }
557 }
558 EXPORT_SYMBOL_GPL(iomap_readahead);
559
560 /*
561 * iomap_is_partially_uptodate checks whether blocks within a folio are
562 * uptodate or not.
563 *
564 * Returns true if all blocks which correspond to the specified part
565 * of the folio are uptodate.
566 */
iomap_is_partially_uptodate(struct folio * folio,size_t from,size_t count)567 bool iomap_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
568 {
569 struct iomap_folio_state *ifs = folio->private;
570 struct inode *inode = folio->mapping->host;
571 unsigned first, last, i;
572
573 if (!ifs)
574 return false;
575
576 /* Caller's range may extend past the end of this folio */
577 count = min(folio_size(folio) - from, count);
578
579 /* First and last blocks in range within folio */
580 first = from >> inode->i_blkbits;
581 last = (from + count - 1) >> inode->i_blkbits;
582
583 for (i = first; i <= last; i++)
584 if (!ifs_block_is_uptodate(ifs, i))
585 return false;
586 return true;
587 }
588 EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate);
589
590 /**
591 * iomap_get_folio - get a folio reference for writing
592 * @iter: iteration structure
593 * @pos: start offset of write
594 * @len: Suggested size of folio to create.
595 *
596 * Returns a locked reference to the folio at @pos, or an error pointer if the
597 * folio could not be obtained.
598 */
iomap_get_folio(struct iomap_iter * iter,loff_t pos,size_t len)599 struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len)
600 {
601 fgf_t fgp = FGP_WRITEBEGIN | FGP_NOFS;
602
603 if (iter->flags & IOMAP_NOWAIT)
604 fgp |= FGP_NOWAIT;
605 if (iter->flags & IOMAP_DONTCACHE)
606 fgp |= FGP_DONTCACHE;
607 fgp |= fgf_set_order(len);
608
609 return __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
610 fgp, mapping_gfp_mask(iter->inode->i_mapping));
611 }
612 EXPORT_SYMBOL_GPL(iomap_get_folio);
613
iomap_release_folio(struct folio * folio,gfp_t gfp_flags)614 bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags)
615 {
616 trace_iomap_release_folio(folio->mapping->host, folio_pos(folio),
617 folio_size(folio));
618
619 /*
620 * If the folio is dirty, we refuse to release our metadata because
621 * it may be partially dirty. Once we track per-block dirty state,
622 * we can release the metadata if every block is dirty.
623 */
624 if (folio_test_dirty(folio))
625 return false;
626 ifs_free(folio);
627 return true;
628 }
629 EXPORT_SYMBOL_GPL(iomap_release_folio);
630
iomap_invalidate_folio(struct folio * folio,size_t offset,size_t len)631 void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len)
632 {
633 trace_iomap_invalidate_folio(folio->mapping->host,
634 folio_pos(folio) + offset, len);
635
636 /*
637 * If we're invalidating the entire folio, clear the dirty state
638 * from it and release it to avoid unnecessary buildup of the LRU.
639 */
640 if (offset == 0 && len == folio_size(folio)) {
641 WARN_ON_ONCE(folio_test_writeback(folio));
642 folio_cancel_dirty(folio);
643 ifs_free(folio);
644 }
645 }
646 EXPORT_SYMBOL_GPL(iomap_invalidate_folio);
647
iomap_dirty_folio(struct address_space * mapping,struct folio * folio)648 bool iomap_dirty_folio(struct address_space *mapping, struct folio *folio)
649 {
650 struct inode *inode = mapping->host;
651 size_t len = folio_size(folio);
652
653 ifs_alloc(inode, folio, 0);
654 iomap_set_range_dirty(folio, 0, len);
655 return filemap_dirty_folio(mapping, folio);
656 }
657 EXPORT_SYMBOL_GPL(iomap_dirty_folio);
658
659 static void
iomap_write_failed(struct inode * inode,loff_t pos,unsigned len)660 iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
661 {
662 loff_t i_size = i_size_read(inode);
663
664 /*
665 * Only truncate newly allocated pages beyoned EOF, even if the
666 * write started inside the existing inode size.
667 */
668 if (pos + len > i_size)
669 truncate_pagecache_range(inode, max(pos, i_size),
670 pos + len - 1);
671 }
672
iomap_read_folio_sync(loff_t block_start,struct folio * folio,size_t poff,size_t plen,const struct iomap * iomap)673 static int iomap_read_folio_sync(loff_t block_start, struct folio *folio,
674 size_t poff, size_t plen, const struct iomap *iomap)
675 {
676 struct bio_vec bvec;
677 struct bio bio;
678
679 bio_init(&bio, iomap->bdev, &bvec, 1, REQ_OP_READ);
680 bio.bi_iter.bi_sector = iomap_sector(iomap, block_start);
681 bio_add_folio_nofail(&bio, folio, plen, poff);
682 return submit_bio_wait(&bio);
683 }
684
__iomap_write_begin(const struct iomap_iter * iter,size_t len,struct folio * folio)685 static int __iomap_write_begin(const struct iomap_iter *iter, size_t len,
686 struct folio *folio)
687 {
688 const struct iomap *srcmap = iomap_iter_srcmap(iter);
689 struct iomap_folio_state *ifs;
690 loff_t pos = iter->pos;
691 loff_t block_size = i_blocksize(iter->inode);
692 loff_t block_start = round_down(pos, block_size);
693 loff_t block_end = round_up(pos + len, block_size);
694 unsigned int nr_blocks = i_blocks_per_folio(iter->inode, folio);
695 size_t from = offset_in_folio(folio, pos), to = from + len;
696 size_t poff, plen;
697
698 /*
699 * If the write or zeroing completely overlaps the current folio, then
700 * entire folio will be dirtied so there is no need for
701 * per-block state tracking structures to be attached to this folio.
702 * For the unshare case, we must read in the ondisk contents because we
703 * are not changing pagecache contents.
704 */
705 if (!(iter->flags & IOMAP_UNSHARE) && pos <= folio_pos(folio) &&
706 pos + len >= folio_pos(folio) + folio_size(folio))
707 return 0;
708
709 ifs = ifs_alloc(iter->inode, folio, iter->flags);
710 if ((iter->flags & IOMAP_NOWAIT) && !ifs && nr_blocks > 1)
711 return -EAGAIN;
712
713 if (folio_test_uptodate(folio))
714 return 0;
715
716 do {
717 iomap_adjust_read_range(iter->inode, folio, &block_start,
718 block_end - block_start, &poff, &plen);
719 if (plen == 0)
720 break;
721
722 if (!(iter->flags & IOMAP_UNSHARE) &&
723 (from <= poff || from >= poff + plen) &&
724 (to <= poff || to >= poff + plen))
725 continue;
726
727 if (iomap_block_needs_zeroing(iter, block_start)) {
728 if (WARN_ON_ONCE(iter->flags & IOMAP_UNSHARE))
729 return -EIO;
730 folio_zero_segments(folio, poff, from, to, poff + plen);
731 } else {
732 int status;
733
734 if (iter->flags & IOMAP_NOWAIT)
735 return -EAGAIN;
736
737 status = iomap_read_folio_sync(block_start, folio,
738 poff, plen, srcmap);
739 if (status)
740 return status;
741 }
742 iomap_set_range_uptodate(folio, poff, plen);
743 } while ((block_start += plen) < block_end);
744
745 return 0;
746 }
747
__iomap_get_folio(struct iomap_iter * iter,size_t len)748 static struct folio *__iomap_get_folio(struct iomap_iter *iter, size_t len)
749 {
750 const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
751 loff_t pos = iter->pos;
752
753 if (!mapping_large_folio_support(iter->inode->i_mapping))
754 len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos));
755
756 if (folio_ops && folio_ops->get_folio)
757 return folio_ops->get_folio(iter, pos, len);
758 else
759 return iomap_get_folio(iter, pos, len);
760 }
761
__iomap_put_folio(struct iomap_iter * iter,size_t ret,struct folio * folio)762 static void __iomap_put_folio(struct iomap_iter *iter, size_t ret,
763 struct folio *folio)
764 {
765 const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
766 loff_t pos = iter->pos;
767
768 if (folio_ops && folio_ops->put_folio) {
769 folio_ops->put_folio(iter->inode, pos, ret, folio);
770 } else {
771 folio_unlock(folio);
772 folio_put(folio);
773 }
774 }
775
776 /* trim pos and bytes to within a given folio */
iomap_trim_folio_range(struct iomap_iter * iter,struct folio * folio,size_t * offset,u64 * bytes)777 static loff_t iomap_trim_folio_range(struct iomap_iter *iter,
778 struct folio *folio, size_t *offset, u64 *bytes)
779 {
780 loff_t pos = iter->pos;
781 size_t fsize = folio_size(folio);
782
783 WARN_ON_ONCE(pos < folio_pos(folio));
784 WARN_ON_ONCE(pos >= folio_pos(folio) + fsize);
785
786 *offset = offset_in_folio(folio, pos);
787 *bytes = min(*bytes, fsize - *offset);
788
789 return pos;
790 }
791
iomap_write_begin_inline(const struct iomap_iter * iter,struct folio * folio)792 static int iomap_write_begin_inline(const struct iomap_iter *iter,
793 struct folio *folio)
794 {
795 /* needs more work for the tailpacking case; disable for now */
796 if (WARN_ON_ONCE(iomap_iter_srcmap(iter)->offset != 0))
797 return -EIO;
798 return iomap_read_inline_data(iter, folio);
799 }
800
801 /*
802 * Grab and prepare a folio for write based on iter state. Returns the folio,
803 * offset, and length. Callers can optionally pass a max length *plen,
804 * otherwise init to zero.
805 */
iomap_write_begin(struct iomap_iter * iter,struct folio ** foliop,size_t * poffset,u64 * plen)806 static int iomap_write_begin(struct iomap_iter *iter, struct folio **foliop,
807 size_t *poffset, u64 *plen)
808 {
809 const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
810 const struct iomap *srcmap = iomap_iter_srcmap(iter);
811 loff_t pos = iter->pos;
812 u64 len = min_t(u64, SIZE_MAX, iomap_length(iter));
813 struct folio *folio;
814 int status = 0;
815
816 len = min_not_zero(len, *plen);
817 BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
818 if (srcmap != &iter->iomap)
819 BUG_ON(pos + len > srcmap->offset + srcmap->length);
820
821 if (fatal_signal_pending(current))
822 return -EINTR;
823
824 folio = __iomap_get_folio(iter, len);
825 if (IS_ERR(folio))
826 return PTR_ERR(folio);
827
828 /*
829 * Now we have a locked folio, before we do anything with it we need to
830 * check that the iomap we have cached is not stale. The inode extent
831 * mapping can change due to concurrent IO in flight (e.g.
832 * IOMAP_UNWRITTEN state can change and memory reclaim could have
833 * reclaimed a previously partially written page at this index after IO
834 * completion before this write reaches this file offset) and hence we
835 * could do the wrong thing here (zero a page range incorrectly or fail
836 * to zero) and corrupt data.
837 */
838 if (folio_ops && folio_ops->iomap_valid) {
839 bool iomap_valid = folio_ops->iomap_valid(iter->inode,
840 &iter->iomap);
841 if (!iomap_valid) {
842 iter->iomap.flags |= IOMAP_F_STALE;
843 status = 0;
844 goto out_unlock;
845 }
846 }
847
848 pos = iomap_trim_folio_range(iter, folio, poffset, &len);
849
850 if (srcmap->type == IOMAP_INLINE)
851 status = iomap_write_begin_inline(iter, folio);
852 else if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
853 status = __block_write_begin_int(folio, pos, len, NULL, srcmap);
854 else
855 status = __iomap_write_begin(iter, len, folio);
856
857 if (unlikely(status))
858 goto out_unlock;
859
860 *foliop = folio;
861 *plen = len;
862 return 0;
863
864 out_unlock:
865 __iomap_put_folio(iter, 0, folio);
866
867 return status;
868 }
869
__iomap_write_end(struct inode * inode,loff_t pos,size_t len,size_t copied,struct folio * folio)870 static bool __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
871 size_t copied, struct folio *folio)
872 {
873 flush_dcache_folio(folio);
874
875 /*
876 * The blocks that were entirely written will now be uptodate, so we
877 * don't have to worry about a read_folio reading them and overwriting a
878 * partial write. However, if we've encountered a short write and only
879 * partially written into a block, it will not be marked uptodate, so a
880 * read_folio might come in and destroy our partial write.
881 *
882 * Do the simplest thing and just treat any short write to a
883 * non-uptodate page as a zero-length write, and force the caller to
884 * redo the whole thing.
885 */
886 if (unlikely(copied < len && !folio_test_uptodate(folio)))
887 return false;
888 iomap_set_range_uptodate(folio, offset_in_folio(folio, pos), len);
889 iomap_set_range_dirty(folio, offset_in_folio(folio, pos), copied);
890 filemap_dirty_folio(inode->i_mapping, folio);
891 return true;
892 }
893
iomap_write_end_inline(const struct iomap_iter * iter,struct folio * folio,loff_t pos,size_t copied)894 static void iomap_write_end_inline(const struct iomap_iter *iter,
895 struct folio *folio, loff_t pos, size_t copied)
896 {
897 const struct iomap *iomap = &iter->iomap;
898 void *addr;
899
900 WARN_ON_ONCE(!folio_test_uptodate(folio));
901 BUG_ON(!iomap_inline_data_valid(iomap));
902
903 flush_dcache_folio(folio);
904 addr = kmap_local_folio(folio, pos);
905 memcpy(iomap_inline_data(iomap, pos), addr, copied);
906 kunmap_local(addr);
907
908 mark_inode_dirty(iter->inode);
909 }
910
911 /*
912 * Returns true if all copied bytes have been written to the pagecache,
913 * otherwise return false.
914 */
iomap_write_end(struct iomap_iter * iter,size_t len,size_t copied,struct folio * folio)915 static bool iomap_write_end(struct iomap_iter *iter, size_t len, size_t copied,
916 struct folio *folio)
917 {
918 const struct iomap *srcmap = iomap_iter_srcmap(iter);
919 loff_t pos = iter->pos;
920
921 if (srcmap->type == IOMAP_INLINE) {
922 iomap_write_end_inline(iter, folio, pos, copied);
923 return true;
924 }
925
926 if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
927 size_t bh_written;
928
929 bh_written = block_write_end(NULL, iter->inode->i_mapping, pos,
930 len, copied, folio, NULL);
931 WARN_ON_ONCE(bh_written != copied && bh_written != 0);
932 return bh_written == copied;
933 }
934
935 return __iomap_write_end(iter->inode, pos, len, copied, folio);
936 }
937
iomap_write_iter(struct iomap_iter * iter,struct iov_iter * i)938 static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
939 {
940 ssize_t total_written = 0;
941 int status = 0;
942 struct address_space *mapping = iter->inode->i_mapping;
943 size_t chunk = mapping_max_folio_size(mapping);
944 unsigned int bdp_flags = (iter->flags & IOMAP_NOWAIT) ? BDP_ASYNC : 0;
945
946 do {
947 struct folio *folio;
948 loff_t old_size;
949 size_t offset; /* Offset into folio */
950 u64 bytes; /* Bytes to write to folio */
951 size_t copied; /* Bytes copied from user */
952 u64 written; /* Bytes have been written */
953 loff_t pos;
954
955 bytes = iov_iter_count(i);
956 retry:
957 offset = iter->pos & (chunk - 1);
958 bytes = min(chunk - offset, bytes);
959 status = balance_dirty_pages_ratelimited_flags(mapping,
960 bdp_flags);
961 if (unlikely(status))
962 break;
963
964 if (bytes > iomap_length(iter))
965 bytes = iomap_length(iter);
966
967 /*
968 * Bring in the user page that we'll copy from _first_.
969 * Otherwise there's a nasty deadlock on copying from the
970 * same page as we're writing to, without it being marked
971 * up-to-date.
972 *
973 * For async buffered writes the assumption is that the user
974 * page has already been faulted in. This can be optimized by
975 * faulting the user page.
976 */
977 if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
978 status = -EFAULT;
979 break;
980 }
981
982 status = iomap_write_begin(iter, &folio, &offset, &bytes);
983 if (unlikely(status)) {
984 iomap_write_failed(iter->inode, iter->pos, bytes);
985 break;
986 }
987 if (iter->iomap.flags & IOMAP_F_STALE)
988 break;
989
990 pos = iter->pos;
991
992 if (mapping_writably_mapped(mapping))
993 flush_dcache_folio(folio);
994
995 copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
996 written = iomap_write_end(iter, bytes, copied, folio) ?
997 copied : 0;
998
999 /*
1000 * Update the in-memory inode size after copying the data into
1001 * the page cache. It's up to the file system to write the
1002 * updated size to disk, preferably after I/O completion so that
1003 * no stale data is exposed. Only once that's done can we
1004 * unlock and release the folio.
1005 */
1006 old_size = iter->inode->i_size;
1007 if (pos + written > old_size) {
1008 i_size_write(iter->inode, pos + written);
1009 iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
1010 }
1011 __iomap_put_folio(iter, written, folio);
1012
1013 if (old_size < pos)
1014 pagecache_isize_extended(iter->inode, old_size, pos);
1015
1016 cond_resched();
1017 if (unlikely(written == 0)) {
1018 /*
1019 * A short copy made iomap_write_end() reject the
1020 * thing entirely. Might be memory poisoning
1021 * halfway through, might be a race with munmap,
1022 * might be severe memory pressure.
1023 */
1024 iomap_write_failed(iter->inode, pos, bytes);
1025 iov_iter_revert(i, copied);
1026
1027 if (chunk > PAGE_SIZE)
1028 chunk /= 2;
1029 if (copied) {
1030 bytes = copied;
1031 goto retry;
1032 }
1033 } else {
1034 total_written += written;
1035 iomap_iter_advance(iter, &written);
1036 }
1037 } while (iov_iter_count(i) && iomap_length(iter));
1038
1039 return total_written ? 0 : status;
1040 }
1041
1042 ssize_t
iomap_file_buffered_write(struct kiocb * iocb,struct iov_iter * i,const struct iomap_ops * ops,void * private)1043 iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
1044 const struct iomap_ops *ops, void *private)
1045 {
1046 struct iomap_iter iter = {
1047 .inode = iocb->ki_filp->f_mapping->host,
1048 .pos = iocb->ki_pos,
1049 .len = iov_iter_count(i),
1050 .flags = IOMAP_WRITE,
1051 .private = private,
1052 };
1053 ssize_t ret;
1054
1055 if (iocb->ki_flags & IOCB_NOWAIT)
1056 iter.flags |= IOMAP_NOWAIT;
1057 if (iocb->ki_flags & IOCB_DONTCACHE)
1058 iter.flags |= IOMAP_DONTCACHE;
1059
1060 while ((ret = iomap_iter(&iter, ops)) > 0)
1061 iter.status = iomap_write_iter(&iter, i);
1062
1063 if (unlikely(iter.pos == iocb->ki_pos))
1064 return ret;
1065 ret = iter.pos - iocb->ki_pos;
1066 iocb->ki_pos = iter.pos;
1067 return ret;
1068 }
1069 EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
1070
iomap_write_delalloc_ifs_punch(struct inode * inode,struct folio * folio,loff_t start_byte,loff_t end_byte,struct iomap * iomap,iomap_punch_t punch)1071 static void iomap_write_delalloc_ifs_punch(struct inode *inode,
1072 struct folio *folio, loff_t start_byte, loff_t end_byte,
1073 struct iomap *iomap, iomap_punch_t punch)
1074 {
1075 unsigned int first_blk, last_blk, i;
1076 loff_t last_byte;
1077 u8 blkbits = inode->i_blkbits;
1078 struct iomap_folio_state *ifs;
1079
1080 /*
1081 * When we have per-block dirty tracking, there can be
1082 * blocks within a folio which are marked uptodate
1083 * but not dirty. In that case it is necessary to punch
1084 * out such blocks to avoid leaking any delalloc blocks.
1085 */
1086 ifs = folio->private;
1087 if (!ifs)
1088 return;
1089
1090 last_byte = min_t(loff_t, end_byte - 1,
1091 folio_pos(folio) + folio_size(folio) - 1);
1092 first_blk = offset_in_folio(folio, start_byte) >> blkbits;
1093 last_blk = offset_in_folio(folio, last_byte) >> blkbits;
1094 for (i = first_blk; i <= last_blk; i++) {
1095 if (!ifs_block_is_dirty(folio, ifs, i))
1096 punch(inode, folio_pos(folio) + (i << blkbits),
1097 1 << blkbits, iomap);
1098 }
1099 }
1100
iomap_write_delalloc_punch(struct inode * inode,struct folio * folio,loff_t * punch_start_byte,loff_t start_byte,loff_t end_byte,struct iomap * iomap,iomap_punch_t punch)1101 static void iomap_write_delalloc_punch(struct inode *inode, struct folio *folio,
1102 loff_t *punch_start_byte, loff_t start_byte, loff_t end_byte,
1103 struct iomap *iomap, iomap_punch_t punch)
1104 {
1105 if (!folio_test_dirty(folio))
1106 return;
1107
1108 /* if dirty, punch up to offset */
1109 if (start_byte > *punch_start_byte) {
1110 punch(inode, *punch_start_byte, start_byte - *punch_start_byte,
1111 iomap);
1112 }
1113
1114 /* Punch non-dirty blocks within folio */
1115 iomap_write_delalloc_ifs_punch(inode, folio, start_byte, end_byte,
1116 iomap, punch);
1117
1118 /*
1119 * Make sure the next punch start is correctly bound to
1120 * the end of this data range, not the end of the folio.
1121 */
1122 *punch_start_byte = min_t(loff_t, end_byte,
1123 folio_pos(folio) + folio_size(folio));
1124 }
1125
1126 /*
1127 * Scan the data range passed to us for dirty page cache folios. If we find a
1128 * dirty folio, punch out the preceding range and update the offset from which
1129 * the next punch will start from.
1130 *
1131 * We can punch out storage reservations under clean pages because they either
1132 * contain data that has been written back - in which case the delalloc punch
1133 * over that range is a no-op - or they have been read faults in which case they
1134 * contain zeroes and we can remove the delalloc backing range and any new
1135 * writes to those pages will do the normal hole filling operation...
1136 *
1137 * This makes the logic simple: we only need to keep the delalloc extents only
1138 * over the dirty ranges of the page cache.
1139 *
1140 * This function uses [start_byte, end_byte) intervals (i.e. open ended) to
1141 * simplify range iterations.
1142 */
iomap_write_delalloc_scan(struct inode * inode,loff_t * punch_start_byte,loff_t start_byte,loff_t end_byte,struct iomap * iomap,iomap_punch_t punch)1143 static void iomap_write_delalloc_scan(struct inode *inode,
1144 loff_t *punch_start_byte, loff_t start_byte, loff_t end_byte,
1145 struct iomap *iomap, iomap_punch_t punch)
1146 {
1147 while (start_byte < end_byte) {
1148 struct folio *folio;
1149
1150 /* grab locked page */
1151 folio = filemap_lock_folio(inode->i_mapping,
1152 start_byte >> PAGE_SHIFT);
1153 if (IS_ERR(folio)) {
1154 start_byte = ALIGN_DOWN(start_byte, PAGE_SIZE) +
1155 PAGE_SIZE;
1156 continue;
1157 }
1158
1159 iomap_write_delalloc_punch(inode, folio, punch_start_byte,
1160 start_byte, end_byte, iomap, punch);
1161
1162 /* move offset to start of next folio in range */
1163 start_byte = folio_pos(folio) + folio_size(folio);
1164 folio_unlock(folio);
1165 folio_put(folio);
1166 }
1167 }
1168
1169 /*
1170 * When a short write occurs, the filesystem might need to use ->iomap_end
1171 * to remove space reservations created in ->iomap_begin.
1172 *
1173 * For filesystems that use delayed allocation, there can be dirty pages over
1174 * the delalloc extent outside the range of a short write but still within the
1175 * delalloc extent allocated for this iomap if the write raced with page
1176 * faults.
1177 *
1178 * Punch out all the delalloc blocks in the range given except for those that
1179 * have dirty data still pending in the page cache - those are going to be
1180 * written and so must still retain the delalloc backing for writeback.
1181 *
1182 * The punch() callback *must* only punch delalloc extents in the range passed
1183 * to it. It must skip over all other types of extents in the range and leave
1184 * them completely unchanged. It must do this punch atomically with respect to
1185 * other extent modifications.
1186 *
1187 * The punch() callback may be called with a folio locked to prevent writeback
1188 * extent allocation racing at the edge of the range we are currently punching.
1189 * The locked folio may or may not cover the range being punched, so it is not
1190 * safe for the punch() callback to lock folios itself.
1191 *
1192 * Lock order is:
1193 *
1194 * inode->i_rwsem (shared or exclusive)
1195 * inode->i_mapping->invalidate_lock (exclusive)
1196 * folio_lock()
1197 * ->punch
1198 * internal filesystem allocation lock
1199 *
1200 * As we are scanning the page cache for data, we don't need to reimplement the
1201 * wheel - mapping_seek_hole_data() does exactly what we need to identify the
1202 * start and end of data ranges correctly even for sub-folio block sizes. This
1203 * byte range based iteration is especially convenient because it means we
1204 * don't have to care about variable size folios, nor where the start or end of
1205 * the data range lies within a folio, if they lie within the same folio or even
1206 * if there are multiple discontiguous data ranges within the folio.
1207 *
1208 * It should be noted that mapping_seek_hole_data() is not aware of EOF, and so
1209 * can return data ranges that exist in the cache beyond EOF. e.g. a page fault
1210 * spanning EOF will initialise the post-EOF data to zeroes and mark it up to
1211 * date. A write page fault can then mark it dirty. If we then fail a write()
1212 * beyond EOF into that up to date cached range, we allocate a delalloc block
1213 * beyond EOF and then have to punch it out. Because the range is up to date,
1214 * mapping_seek_hole_data() will return it, and we will skip the punch because
1215 * the folio is dirty. THis is incorrect - we always need to punch out delalloc
1216 * beyond EOF in this case as writeback will never write back and covert that
1217 * delalloc block beyond EOF. Hence we limit the cached data scan range to EOF,
1218 * resulting in always punching out the range from the EOF to the end of the
1219 * range the iomap spans.
1220 *
1221 * Intervals are of the form [start_byte, end_byte) (i.e. open ended) because it
1222 * matches the intervals returned by mapping_seek_hole_data(). i.e. SEEK_DATA
1223 * returns the start of a data range (start_byte), and SEEK_HOLE(start_byte)
1224 * returns the end of the data range (data_end). Using closed intervals would
1225 * require sprinkling this code with magic "+ 1" and "- 1" arithmetic and expose
1226 * the code to subtle off-by-one bugs....
1227 */
iomap_write_delalloc_release(struct inode * inode,loff_t start_byte,loff_t end_byte,unsigned flags,struct iomap * iomap,iomap_punch_t punch)1228 void iomap_write_delalloc_release(struct inode *inode, loff_t start_byte,
1229 loff_t end_byte, unsigned flags, struct iomap *iomap,
1230 iomap_punch_t punch)
1231 {
1232 loff_t punch_start_byte = start_byte;
1233 loff_t scan_end_byte = min(i_size_read(inode), end_byte);
1234
1235 /*
1236 * The caller must hold invalidate_lock to avoid races with page faults
1237 * re-instantiating folios and dirtying them via ->page_mkwrite whilst
1238 * we walk the cache and perform delalloc extent removal. Failing to do
1239 * this can leave dirty pages with no space reservation in the cache.
1240 */
1241 lockdep_assert_held_write(&inode->i_mapping->invalidate_lock);
1242
1243 while (start_byte < scan_end_byte) {
1244 loff_t data_end;
1245
1246 start_byte = mapping_seek_hole_data(inode->i_mapping,
1247 start_byte, scan_end_byte, SEEK_DATA);
1248 /*
1249 * If there is no more data to scan, all that is left is to
1250 * punch out the remaining range.
1251 *
1252 * Note that mapping_seek_hole_data is only supposed to return
1253 * either an offset or -ENXIO, so WARN on any other error as
1254 * that would be an API change without updating the callers.
1255 */
1256 if (start_byte == -ENXIO || start_byte == scan_end_byte)
1257 break;
1258 if (WARN_ON_ONCE(start_byte < 0))
1259 return;
1260 WARN_ON_ONCE(start_byte < punch_start_byte);
1261 WARN_ON_ONCE(start_byte > scan_end_byte);
1262
1263 /*
1264 * We find the end of this contiguous cached data range by
1265 * seeking from start_byte to the beginning of the next hole.
1266 */
1267 data_end = mapping_seek_hole_data(inode->i_mapping, start_byte,
1268 scan_end_byte, SEEK_HOLE);
1269 if (WARN_ON_ONCE(data_end < 0))
1270 return;
1271
1272 /*
1273 * If we race with post-direct I/O invalidation of the page cache,
1274 * there might be no data left at start_byte.
1275 */
1276 if (data_end == start_byte)
1277 continue;
1278
1279 WARN_ON_ONCE(data_end < start_byte);
1280 WARN_ON_ONCE(data_end > scan_end_byte);
1281
1282 iomap_write_delalloc_scan(inode, &punch_start_byte, start_byte,
1283 data_end, iomap, punch);
1284
1285 /* The next data search starts at the end of this one. */
1286 start_byte = data_end;
1287 }
1288
1289 if (punch_start_byte < end_byte)
1290 punch(inode, punch_start_byte, end_byte - punch_start_byte,
1291 iomap);
1292 }
1293 EXPORT_SYMBOL_GPL(iomap_write_delalloc_release);
1294
iomap_unshare_iter(struct iomap_iter * iter)1295 static int iomap_unshare_iter(struct iomap_iter *iter)
1296 {
1297 struct iomap *iomap = &iter->iomap;
1298 u64 bytes = iomap_length(iter);
1299 int status;
1300
1301 if (!iomap_want_unshare_iter(iter))
1302 return iomap_iter_advance(iter, &bytes);
1303
1304 do {
1305 struct folio *folio;
1306 size_t offset;
1307 bool ret;
1308
1309 bytes = min_t(u64, SIZE_MAX, bytes);
1310 status = iomap_write_begin(iter, &folio, &offset, &bytes);
1311 if (unlikely(status))
1312 return status;
1313 if (iomap->flags & IOMAP_F_STALE)
1314 break;
1315
1316 ret = iomap_write_end(iter, bytes, bytes, folio);
1317 __iomap_put_folio(iter, bytes, folio);
1318 if (WARN_ON_ONCE(!ret))
1319 return -EIO;
1320
1321 cond_resched();
1322
1323 balance_dirty_pages_ratelimited(iter->inode->i_mapping);
1324
1325 status = iomap_iter_advance(iter, &bytes);
1326 if (status)
1327 break;
1328 } while (bytes > 0);
1329
1330 return status;
1331 }
1332
1333 int
iomap_file_unshare(struct inode * inode,loff_t pos,loff_t len,const struct iomap_ops * ops)1334 iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
1335 const struct iomap_ops *ops)
1336 {
1337 struct iomap_iter iter = {
1338 .inode = inode,
1339 .pos = pos,
1340 .flags = IOMAP_WRITE | IOMAP_UNSHARE,
1341 };
1342 loff_t size = i_size_read(inode);
1343 int ret;
1344
1345 if (pos < 0 || pos >= size)
1346 return 0;
1347
1348 iter.len = min(len, size - pos);
1349 while ((ret = iomap_iter(&iter, ops)) > 0)
1350 iter.status = iomap_unshare_iter(&iter);
1351 return ret;
1352 }
1353 EXPORT_SYMBOL_GPL(iomap_file_unshare);
1354
1355 /*
1356 * Flush the remaining range of the iter and mark the current mapping stale.
1357 * This is used when zero range sees an unwritten mapping that may have had
1358 * dirty pagecache over it.
1359 */
iomap_zero_iter_flush_and_stale(struct iomap_iter * i)1360 static inline int iomap_zero_iter_flush_and_stale(struct iomap_iter *i)
1361 {
1362 struct address_space *mapping = i->inode->i_mapping;
1363 loff_t end = i->pos + i->len - 1;
1364
1365 i->iomap.flags |= IOMAP_F_STALE;
1366 return filemap_write_and_wait_range(mapping, i->pos, end);
1367 }
1368
iomap_zero_iter(struct iomap_iter * iter,bool * did_zero)1369 static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
1370 {
1371 u64 bytes = iomap_length(iter);
1372 int status;
1373
1374 do {
1375 struct folio *folio;
1376 size_t offset;
1377 bool ret;
1378
1379 bytes = min_t(u64, SIZE_MAX, bytes);
1380 status = iomap_write_begin(iter, &folio, &offset, &bytes);
1381 if (status)
1382 return status;
1383 if (iter->iomap.flags & IOMAP_F_STALE)
1384 break;
1385
1386 /* warn about zeroing folios beyond eof that won't write back */
1387 WARN_ON_ONCE(folio_pos(folio) > iter->inode->i_size);
1388
1389 folio_zero_range(folio, offset, bytes);
1390 folio_mark_accessed(folio);
1391
1392 ret = iomap_write_end(iter, bytes, bytes, folio);
1393 __iomap_put_folio(iter, bytes, folio);
1394 if (WARN_ON_ONCE(!ret))
1395 return -EIO;
1396
1397 status = iomap_iter_advance(iter, &bytes);
1398 if (status)
1399 break;
1400 } while (bytes > 0);
1401
1402 if (did_zero)
1403 *did_zero = true;
1404 return status;
1405 }
1406
1407 int
iomap_zero_range(struct inode * inode,loff_t pos,loff_t len,bool * did_zero,const struct iomap_ops * ops,void * private)1408 iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
1409 const struct iomap_ops *ops, void *private)
1410 {
1411 struct iomap_iter iter = {
1412 .inode = inode,
1413 .pos = pos,
1414 .len = len,
1415 .flags = IOMAP_ZERO,
1416 .private = private,
1417 };
1418 struct address_space *mapping = inode->i_mapping;
1419 unsigned int blocksize = i_blocksize(inode);
1420 unsigned int off = pos & (blocksize - 1);
1421 loff_t plen = min_t(loff_t, len, blocksize - off);
1422 int ret;
1423 bool range_dirty;
1424
1425 /*
1426 * Zero range can skip mappings that are zero on disk so long as
1427 * pagecache is clean. If pagecache was dirty prior to zero range, the
1428 * mapping converts on writeback completion and so must be zeroed.
1429 *
1430 * The simplest way to deal with this across a range is to flush
1431 * pagecache and process the updated mappings. To avoid excessive
1432 * flushing on partial eof zeroing, special case it to zero the
1433 * unaligned start portion if already dirty in pagecache.
1434 */
1435 if (off &&
1436 filemap_range_needs_writeback(mapping, pos, pos + plen - 1)) {
1437 iter.len = plen;
1438 while ((ret = iomap_iter(&iter, ops)) > 0)
1439 iter.status = iomap_zero_iter(&iter, did_zero);
1440
1441 iter.len = len - (iter.pos - pos);
1442 if (ret || !iter.len)
1443 return ret;
1444 }
1445
1446 /*
1447 * To avoid an unconditional flush, check pagecache state and only flush
1448 * if dirty and the fs returns a mapping that might convert on
1449 * writeback.
1450 */
1451 range_dirty = filemap_range_needs_writeback(inode->i_mapping,
1452 iter.pos, iter.pos + iter.len - 1);
1453 while ((ret = iomap_iter(&iter, ops)) > 0) {
1454 const struct iomap *srcmap = iomap_iter_srcmap(&iter);
1455
1456 if (srcmap->type == IOMAP_HOLE ||
1457 srcmap->type == IOMAP_UNWRITTEN) {
1458 s64 status;
1459
1460 if (range_dirty) {
1461 range_dirty = false;
1462 status = iomap_zero_iter_flush_and_stale(&iter);
1463 } else {
1464 status = iomap_iter_advance_full(&iter);
1465 }
1466 iter.status = status;
1467 continue;
1468 }
1469
1470 iter.status = iomap_zero_iter(&iter, did_zero);
1471 }
1472 return ret;
1473 }
1474 EXPORT_SYMBOL_GPL(iomap_zero_range);
1475
1476 int
iomap_truncate_page(struct inode * inode,loff_t pos,bool * did_zero,const struct iomap_ops * ops,void * private)1477 iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
1478 const struct iomap_ops *ops, void *private)
1479 {
1480 unsigned int blocksize = i_blocksize(inode);
1481 unsigned int off = pos & (blocksize - 1);
1482
1483 /* Block boundary? Nothing to do */
1484 if (!off)
1485 return 0;
1486 return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops,
1487 private);
1488 }
1489 EXPORT_SYMBOL_GPL(iomap_truncate_page);
1490
iomap_folio_mkwrite_iter(struct iomap_iter * iter,struct folio * folio)1491 static int iomap_folio_mkwrite_iter(struct iomap_iter *iter,
1492 struct folio *folio)
1493 {
1494 loff_t length = iomap_length(iter);
1495 int ret;
1496
1497 if (iter->iomap.flags & IOMAP_F_BUFFER_HEAD) {
1498 ret = __block_write_begin_int(folio, iter->pos, length, NULL,
1499 &iter->iomap);
1500 if (ret)
1501 return ret;
1502 block_commit_write(folio, 0, length);
1503 } else {
1504 WARN_ON_ONCE(!folio_test_uptodate(folio));
1505 folio_mark_dirty(folio);
1506 }
1507
1508 return iomap_iter_advance(iter, &length);
1509 }
1510
iomap_page_mkwrite(struct vm_fault * vmf,const struct iomap_ops * ops,void * private)1511 vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops,
1512 void *private)
1513 {
1514 struct iomap_iter iter = {
1515 .inode = file_inode(vmf->vma->vm_file),
1516 .flags = IOMAP_WRITE | IOMAP_FAULT,
1517 .private = private,
1518 };
1519 struct folio *folio = page_folio(vmf->page);
1520 ssize_t ret;
1521
1522 folio_lock(folio);
1523 ret = folio_mkwrite_check_truncate(folio, iter.inode);
1524 if (ret < 0)
1525 goto out_unlock;
1526 iter.pos = folio_pos(folio);
1527 iter.len = ret;
1528 while ((ret = iomap_iter(&iter, ops)) > 0)
1529 iter.status = iomap_folio_mkwrite_iter(&iter, folio);
1530
1531 if (ret < 0)
1532 goto out_unlock;
1533 folio_wait_stable(folio);
1534 return VM_FAULT_LOCKED;
1535 out_unlock:
1536 folio_unlock(folio);
1537 return vmf_fs_error(ret);
1538 }
1539 EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
1540
iomap_finish_folio_write(struct inode * inode,struct folio * folio,size_t len)1541 static void iomap_finish_folio_write(struct inode *inode, struct folio *folio,
1542 size_t len)
1543 {
1544 struct iomap_folio_state *ifs = folio->private;
1545
1546 WARN_ON_ONCE(i_blocks_per_folio(inode, folio) > 1 && !ifs);
1547 WARN_ON_ONCE(ifs && atomic_read(&ifs->write_bytes_pending) <= 0);
1548
1549 if (!ifs || atomic_sub_and_test(len, &ifs->write_bytes_pending))
1550 folio_end_writeback(folio);
1551 }
1552
1553 /*
1554 * We're now finished for good with this ioend structure. Update the page
1555 * state, release holds on bios, and finally free up memory. Do not use the
1556 * ioend after this.
1557 */
iomap_finish_ioend_buffered(struct iomap_ioend * ioend)1558 u32 iomap_finish_ioend_buffered(struct iomap_ioend *ioend)
1559 {
1560 struct inode *inode = ioend->io_inode;
1561 struct bio *bio = &ioend->io_bio;
1562 struct folio_iter fi;
1563 u32 folio_count = 0;
1564
1565 if (ioend->io_error) {
1566 mapping_set_error(inode->i_mapping, ioend->io_error);
1567 if (!bio_flagged(bio, BIO_QUIET)) {
1568 pr_err_ratelimited(
1569 "%s: writeback error on inode %lu, offset %lld, sector %llu",
1570 inode->i_sb->s_id, inode->i_ino,
1571 ioend->io_offset, ioend->io_sector);
1572 }
1573 }
1574
1575 /* walk all folios in bio, ending page IO on them */
1576 bio_for_each_folio_all(fi, bio) {
1577 iomap_finish_folio_write(inode, fi.folio, fi.length);
1578 folio_count++;
1579 }
1580
1581 bio_put(bio); /* frees the ioend */
1582 return folio_count;
1583 }
1584
iomap_writepage_end_bio(struct bio * bio)1585 static void iomap_writepage_end_bio(struct bio *bio)
1586 {
1587 struct iomap_ioend *ioend = iomap_ioend_from_bio(bio);
1588
1589 ioend->io_error = blk_status_to_errno(bio->bi_status);
1590 iomap_finish_ioend_buffered(ioend);
1591 }
1592
1593 /*
1594 * Submit an ioend.
1595 *
1596 * If @error is non-zero, it means that we have a situation where some part of
1597 * the submission process has failed after we've marked pages for writeback.
1598 * We cannot cancel ioend directly in that case, so call the bio end I/O handler
1599 * with the error status here to run the normal I/O completion handler to clear
1600 * the writeback bit and let the file system proess the errors.
1601 */
iomap_submit_ioend(struct iomap_writepage_ctx * wpc,int error)1602 static int iomap_submit_ioend(struct iomap_writepage_ctx *wpc, int error)
1603 {
1604 if (!wpc->ioend)
1605 return error;
1606
1607 /*
1608 * Let the file systems prepare the I/O submission and hook in an I/O
1609 * comletion handler. This also needs to happen in case after a
1610 * failure happened so that the file system end I/O handler gets called
1611 * to clean up.
1612 */
1613 if (wpc->ops->submit_ioend) {
1614 error = wpc->ops->submit_ioend(wpc, error);
1615 } else {
1616 if (WARN_ON_ONCE(wpc->iomap.flags & IOMAP_F_ANON_WRITE))
1617 error = -EIO;
1618 if (!error)
1619 submit_bio(&wpc->ioend->io_bio);
1620 }
1621
1622 if (error) {
1623 wpc->ioend->io_bio.bi_status = errno_to_blk_status(error);
1624 bio_endio(&wpc->ioend->io_bio);
1625 }
1626
1627 wpc->ioend = NULL;
1628 return error;
1629 }
1630
iomap_alloc_ioend(struct iomap_writepage_ctx * wpc,struct writeback_control * wbc,struct inode * inode,loff_t pos,u16 ioend_flags)1631 static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
1632 struct writeback_control *wbc, struct inode *inode, loff_t pos,
1633 u16 ioend_flags)
1634 {
1635 struct bio *bio;
1636
1637 bio = bio_alloc_bioset(wpc->iomap.bdev, BIO_MAX_VECS,
1638 REQ_OP_WRITE | wbc_to_write_flags(wbc),
1639 GFP_NOFS, &iomap_ioend_bioset);
1640 bio->bi_iter.bi_sector = iomap_sector(&wpc->iomap, pos);
1641 bio->bi_end_io = iomap_writepage_end_bio;
1642 bio->bi_write_hint = inode->i_write_hint;
1643 wbc_init_bio(wbc, bio);
1644 wpc->nr_folios = 0;
1645 return iomap_init_ioend(inode, bio, pos, ioend_flags);
1646 }
1647
iomap_can_add_to_ioend(struct iomap_writepage_ctx * wpc,loff_t pos,u16 ioend_flags)1648 static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t pos,
1649 u16 ioend_flags)
1650 {
1651 if (ioend_flags & IOMAP_IOEND_BOUNDARY)
1652 return false;
1653 if ((ioend_flags & IOMAP_IOEND_NOMERGE_FLAGS) !=
1654 (wpc->ioend->io_flags & IOMAP_IOEND_NOMERGE_FLAGS))
1655 return false;
1656 if (pos != wpc->ioend->io_offset + wpc->ioend->io_size)
1657 return false;
1658 if (!(wpc->iomap.flags & IOMAP_F_ANON_WRITE) &&
1659 iomap_sector(&wpc->iomap, pos) !=
1660 bio_end_sector(&wpc->ioend->io_bio))
1661 return false;
1662 /*
1663 * Limit ioend bio chain lengths to minimise IO completion latency. This
1664 * also prevents long tight loops ending page writeback on all the
1665 * folios in the ioend.
1666 */
1667 if (wpc->nr_folios >= IOEND_BATCH_SIZE)
1668 return false;
1669 return true;
1670 }
1671
1672 /*
1673 * Test to see if we have an existing ioend structure that we could append to
1674 * first; otherwise finish off the current ioend and start another.
1675 *
1676 * If a new ioend is created and cached, the old ioend is submitted to the block
1677 * layer instantly. Batching optimisations are provided by higher level block
1678 * plugging.
1679 *
1680 * At the end of a writeback pass, there will be a cached ioend remaining on the
1681 * writepage context that the caller will need to submit.
1682 */
iomap_add_to_ioend(struct iomap_writepage_ctx * wpc,struct writeback_control * wbc,struct folio * folio,struct inode * inode,loff_t pos,loff_t end_pos,unsigned len)1683 static int iomap_add_to_ioend(struct iomap_writepage_ctx *wpc,
1684 struct writeback_control *wbc, struct folio *folio,
1685 struct inode *inode, loff_t pos, loff_t end_pos,
1686 unsigned len)
1687 {
1688 struct iomap_folio_state *ifs = folio->private;
1689 size_t poff = offset_in_folio(folio, pos);
1690 unsigned int ioend_flags = 0;
1691 int error;
1692
1693 if (wpc->iomap.type == IOMAP_UNWRITTEN)
1694 ioend_flags |= IOMAP_IOEND_UNWRITTEN;
1695 if (wpc->iomap.flags & IOMAP_F_SHARED)
1696 ioend_flags |= IOMAP_IOEND_SHARED;
1697 if (folio_test_dropbehind(folio))
1698 ioend_flags |= IOMAP_IOEND_DONTCACHE;
1699 if (pos == wpc->iomap.offset && (wpc->iomap.flags & IOMAP_F_BOUNDARY))
1700 ioend_flags |= IOMAP_IOEND_BOUNDARY;
1701
1702 if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, pos, ioend_flags)) {
1703 new_ioend:
1704 error = iomap_submit_ioend(wpc, 0);
1705 if (error)
1706 return error;
1707 wpc->ioend = iomap_alloc_ioend(wpc, wbc, inode, pos,
1708 ioend_flags);
1709 }
1710
1711 if (!bio_add_folio(&wpc->ioend->io_bio, folio, len, poff))
1712 goto new_ioend;
1713
1714 if (ifs)
1715 atomic_add(len, &ifs->write_bytes_pending);
1716
1717 /*
1718 * Clamp io_offset and io_size to the incore EOF so that ondisk
1719 * file size updates in the ioend completion are byte-accurate.
1720 * This avoids recovering files with zeroed tail regions when
1721 * writeback races with appending writes:
1722 *
1723 * Thread 1: Thread 2:
1724 * ------------ -----------
1725 * write [A, A+B]
1726 * update inode size to A+B
1727 * submit I/O [A, A+BS]
1728 * write [A+B, A+B+C]
1729 * update inode size to A+B+C
1730 * <I/O completes, updates disk size to min(A+B+C, A+BS)>
1731 * <power failure>
1732 *
1733 * After reboot:
1734 * 1) with A+B+C < A+BS, the file has zero padding in range
1735 * [A+B, A+B+C]
1736 *
1737 * |< Block Size (BS) >|
1738 * |DDDDDDDDDDDD0000000000000|
1739 * ^ ^ ^
1740 * A A+B A+B+C
1741 * (EOF)
1742 *
1743 * 2) with A+B+C > A+BS, the file has zero padding in range
1744 * [A+B, A+BS]
1745 *
1746 * |< Block Size (BS) >|< Block Size (BS) >|
1747 * |DDDDDDDDDDDD0000000000000|00000000000000000000000000|
1748 * ^ ^ ^ ^
1749 * A A+B A+BS A+B+C
1750 * (EOF)
1751 *
1752 * D = Valid Data
1753 * 0 = Zero Padding
1754 *
1755 * Note that this defeats the ability to chain the ioends of
1756 * appending writes.
1757 */
1758 wpc->ioend->io_size += len;
1759 if (wpc->ioend->io_offset + wpc->ioend->io_size > end_pos)
1760 wpc->ioend->io_size = end_pos - wpc->ioend->io_offset;
1761
1762 wbc_account_cgroup_owner(wbc, folio, len);
1763 return 0;
1764 }
1765
iomap_writepage_map_blocks(struct iomap_writepage_ctx * wpc,struct writeback_control * wbc,struct folio * folio,struct inode * inode,u64 pos,u64 end_pos,unsigned dirty_len,unsigned * count)1766 static int iomap_writepage_map_blocks(struct iomap_writepage_ctx *wpc,
1767 struct writeback_control *wbc, struct folio *folio,
1768 struct inode *inode, u64 pos, u64 end_pos,
1769 unsigned dirty_len, unsigned *count)
1770 {
1771 int error;
1772
1773 do {
1774 unsigned map_len;
1775
1776 error = wpc->ops->map_blocks(wpc, inode, pos, dirty_len);
1777 if (error)
1778 break;
1779 trace_iomap_writepage_map(inode, pos, dirty_len, &wpc->iomap);
1780
1781 map_len = min_t(u64, dirty_len,
1782 wpc->iomap.offset + wpc->iomap.length - pos);
1783 WARN_ON_ONCE(!folio->private && map_len < dirty_len);
1784
1785 switch (wpc->iomap.type) {
1786 case IOMAP_INLINE:
1787 WARN_ON_ONCE(1);
1788 error = -EIO;
1789 break;
1790 case IOMAP_HOLE:
1791 break;
1792 default:
1793 error = iomap_add_to_ioend(wpc, wbc, folio, inode, pos,
1794 end_pos, map_len);
1795 if (!error)
1796 (*count)++;
1797 break;
1798 }
1799 dirty_len -= map_len;
1800 pos += map_len;
1801 } while (dirty_len && !error);
1802
1803 /*
1804 * We cannot cancel the ioend directly here on error. We may have
1805 * already set other pages under writeback and hence we have to run I/O
1806 * completion to mark the error state of the pages under writeback
1807 * appropriately.
1808 *
1809 * Just let the file system know what portion of the folio failed to
1810 * map.
1811 */
1812 if (error && wpc->ops->discard_folio)
1813 wpc->ops->discard_folio(folio, pos);
1814 return error;
1815 }
1816
1817 /*
1818 * Check interaction of the folio with the file end.
1819 *
1820 * If the folio is entirely beyond i_size, return false. If it straddles
1821 * i_size, adjust end_pos and zero all data beyond i_size.
1822 */
iomap_writepage_handle_eof(struct folio * folio,struct inode * inode,u64 * end_pos)1823 static bool iomap_writepage_handle_eof(struct folio *folio, struct inode *inode,
1824 u64 *end_pos)
1825 {
1826 u64 isize = i_size_read(inode);
1827
1828 if (*end_pos > isize) {
1829 size_t poff = offset_in_folio(folio, isize);
1830 pgoff_t end_index = isize >> PAGE_SHIFT;
1831
1832 /*
1833 * If the folio is entirely ouside of i_size, skip it.
1834 *
1835 * This can happen due to a truncate operation that is in
1836 * progress and in that case truncate will finish it off once
1837 * we've dropped the folio lock.
1838 *
1839 * Note that the pgoff_t used for end_index is an unsigned long.
1840 * If the given offset is greater than 16TB on a 32-bit system,
1841 * then if we checked if the folio is fully outside i_size with
1842 * "if (folio->index >= end_index + 1)", "end_index + 1" would
1843 * overflow and evaluate to 0. Hence this folio would be
1844 * redirtied and written out repeatedly, which would result in
1845 * an infinite loop; the user program performing this operation
1846 * would hang. Instead, we can detect this situation by
1847 * checking if the folio is totally beyond i_size or if its
1848 * offset is just equal to the EOF.
1849 */
1850 if (folio->index > end_index ||
1851 (folio->index == end_index && poff == 0))
1852 return false;
1853
1854 /*
1855 * The folio straddles i_size.
1856 *
1857 * It must be zeroed out on each and every writepage invocation
1858 * because it may be mmapped:
1859 *
1860 * A file is mapped in multiples of the page size. For a
1861 * file that is not a multiple of the page size, the
1862 * remaining memory is zeroed when mapped, and writes to that
1863 * region are not written out to the file.
1864 *
1865 * Also adjust the end_pos to the end of file and skip writeback
1866 * for all blocks entirely beyond i_size.
1867 */
1868 folio_zero_segment(folio, poff, folio_size(folio));
1869 *end_pos = isize;
1870 }
1871
1872 return true;
1873 }
1874
iomap_writepage_map(struct iomap_writepage_ctx * wpc,struct writeback_control * wbc,struct folio * folio)1875 static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
1876 struct writeback_control *wbc, struct folio *folio)
1877 {
1878 struct iomap_folio_state *ifs = folio->private;
1879 struct inode *inode = folio->mapping->host;
1880 u64 pos = folio_pos(folio);
1881 u64 end_pos = pos + folio_size(folio);
1882 u64 end_aligned = 0;
1883 unsigned count = 0;
1884 int error = 0;
1885 u32 rlen;
1886
1887 WARN_ON_ONCE(!folio_test_locked(folio));
1888 WARN_ON_ONCE(folio_test_dirty(folio));
1889 WARN_ON_ONCE(folio_test_writeback(folio));
1890
1891 trace_iomap_writepage(inode, pos, folio_size(folio));
1892
1893 if (!iomap_writepage_handle_eof(folio, inode, &end_pos)) {
1894 folio_unlock(folio);
1895 return 0;
1896 }
1897 WARN_ON_ONCE(end_pos <= pos);
1898
1899 if (i_blocks_per_folio(inode, folio) > 1) {
1900 if (!ifs) {
1901 ifs = ifs_alloc(inode, folio, 0);
1902 iomap_set_range_dirty(folio, 0, end_pos - pos);
1903 }
1904
1905 /*
1906 * Keep the I/O completion handler from clearing the writeback
1907 * bit until we have submitted all blocks by adding a bias to
1908 * ifs->write_bytes_pending, which is dropped after submitting
1909 * all blocks.
1910 */
1911 WARN_ON_ONCE(atomic_read(&ifs->write_bytes_pending) != 0);
1912 atomic_inc(&ifs->write_bytes_pending);
1913 }
1914
1915 /*
1916 * Set the writeback bit ASAP, as the I/O completion for the single
1917 * block per folio case happen hit as soon as we're submitting the bio.
1918 */
1919 folio_start_writeback(folio);
1920
1921 /*
1922 * Walk through the folio to find dirty areas to write back.
1923 */
1924 end_aligned = round_up(end_pos, i_blocksize(inode));
1925 while ((rlen = iomap_find_dirty_range(folio, &pos, end_aligned))) {
1926 error = iomap_writepage_map_blocks(wpc, wbc, folio, inode,
1927 pos, end_pos, rlen, &count);
1928 if (error)
1929 break;
1930 pos += rlen;
1931 }
1932
1933 if (count)
1934 wpc->nr_folios++;
1935
1936 /*
1937 * We can have dirty bits set past end of file in page_mkwrite path
1938 * while mapping the last partial folio. Hence it's better to clear
1939 * all the dirty bits in the folio here.
1940 */
1941 iomap_clear_range_dirty(folio, 0, folio_size(folio));
1942
1943 /*
1944 * Usually the writeback bit is cleared by the I/O completion handler.
1945 * But we may end up either not actually writing any blocks, or (when
1946 * there are multiple blocks in a folio) all I/O might have finished
1947 * already at this point. In that case we need to clear the writeback
1948 * bit ourselves right after unlocking the page.
1949 */
1950 folio_unlock(folio);
1951 if (ifs) {
1952 if (atomic_dec_and_test(&ifs->write_bytes_pending))
1953 folio_end_writeback(folio);
1954 } else {
1955 if (!count)
1956 folio_end_writeback(folio);
1957 }
1958 mapping_set_error(inode->i_mapping, error);
1959 return error;
1960 }
1961
1962 int
iomap_writepages(struct address_space * mapping,struct writeback_control * wbc,struct iomap_writepage_ctx * wpc,const struct iomap_writeback_ops * ops)1963 iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
1964 struct iomap_writepage_ctx *wpc,
1965 const struct iomap_writeback_ops *ops)
1966 {
1967 struct folio *folio = NULL;
1968 int error;
1969
1970 /*
1971 * Writeback from reclaim context should never happen except in the case
1972 * of a VM regression so warn about it and refuse to write the data.
1973 */
1974 if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC | PF_KSWAPD)) ==
1975 PF_MEMALLOC))
1976 return -EIO;
1977
1978 wpc->ops = ops;
1979 while ((folio = writeback_iter(mapping, wbc, folio, &error)))
1980 error = iomap_writepage_map(wpc, wbc, folio);
1981 return iomap_submit_ioend(wpc, error);
1982 }
1983 EXPORT_SYMBOL_GPL(iomap_writepages);
1984