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/list_sort.h>
16	#include <linux/swap.h>
17	#include <linux/bio.h>
18	#include <linux/sched/signal.h>
19	#include <linux/migrate.h>
20	#include "trace.h"
21
22	#include "../internal.h"
23
24	#define IOEND_BATCH_SIZE 4096
25
26	typedef int (*iomap_punch_t)(struct inode *inode, loff_t offset, loff_t length);
27	/*
28	* Structure allocated for each folio to track per-block uptodate, dirty state
29	* and I/O completions.
30	*/
31	struct iomap_folio_state {
32	spinlock_t state_lock;
33	unsigned int read_bytes_pending;
34	atomic_t write_bytes_pending;
35
36	/*
37	* Each block has two bits in this bitmap:
38	* Bits [0..blocks_per_folio) has the uptodate status.
39	* Bits [b_p_f...(2*b_p_f)) has the dirty status.
40	*/
41	unsigned long state[];
42	};
43
44	static struct bio_set iomap_ioend_bioset;
45
46	static inline bool ifs_is_fully_uptodate(struct folio *folio,
47	struct iomap_folio_state *ifs)
48	{
49	struct inode *inode = folio->mapping->host;
50
51	return bitmap_full(src: ifs->state, nbits: i_blocks_per_folio(inode, folio));
52	}
53
54	static inline bool ifs_block_is_uptodate(struct iomap_folio_state *ifs,
55	unsigned int block)
56	{
57	return test_bit(block, ifs->state);
58	}
59
60	static bool ifs_set_range_uptodate(struct folio *folio,
61	struct iomap_folio_state *ifs, size_t off, size_t len)
62	{
63	struct inode *inode = folio->mapping->host;
64	unsigned int first_blk = off >> inode->i_blkbits;
65	unsigned int last_blk = (off + len - 1) >> inode->i_blkbits;
66	unsigned int nr_blks = last_blk - first_blk + 1;
67
68	bitmap_set(map: ifs->state, start: first_blk, nbits: nr_blks);
69	return ifs_is_fully_uptodate(folio, ifs);
70	}
71
72	static void iomap_set_range_uptodate(struct folio *folio, size_t off,
73	size_t len)
74	{
75	struct iomap_folio_state *ifs = folio->private;
76	unsigned long flags;
77	bool uptodate = true;
78
79	if (ifs) {
80	spin_lock_irqsave(&ifs->state_lock, flags);
81	uptodate = ifs_set_range_uptodate(folio, ifs, off, len);
82	spin_unlock_irqrestore(lock: &ifs->state_lock, flags);
83	}
84
85	if (uptodate)
86	folio_mark_uptodate(folio);
87	}
88
89	static inline bool ifs_block_is_dirty(struct folio *folio,
90	struct iomap_folio_state *ifs, int block)
91	{
92	struct inode *inode = folio->mapping->host;
93	unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
94
95	return test_bit(block + blks_per_folio, ifs->state);
96	}
97
98	static unsigned ifs_find_dirty_range(struct folio *folio,
99	struct iomap_folio_state *ifs, u64 *range_start, u64 range_end)
100	{
101	struct inode *inode = folio->mapping->host;
102	unsigned start_blk =
103	offset_in_folio(folio, *range_start) >> inode->i_blkbits;
104	unsigned end_blk = min_not_zero(
105	offset_in_folio(folio, range_end) >> inode->i_blkbits,
106	i_blocks_per_folio(inode, folio));
107	unsigned nblks = 1;
108
109	while (!ifs_block_is_dirty(folio, ifs, block: start_blk))
110	if (++start_blk == end_blk)
111	return 0;
112
113	while (start_blk + nblks < end_blk) {
114	if (!ifs_block_is_dirty(folio, ifs, block: start_blk + nblks))
115	break;
116	nblks++;
117	}
118
119	*range_start = folio_pos(folio) + (start_blk << inode->i_blkbits);
120	return nblks << inode->i_blkbits;
121	}
122
123	static unsigned iomap_find_dirty_range(struct folio *folio, u64 *range_start,
124	u64 range_end)
125	{
126	struct iomap_folio_state *ifs = folio->private;
127
128	if (*range_start >= range_end)
129	return 0;
130
131	if (ifs)
132	return ifs_find_dirty_range(folio, ifs, range_start, range_end);
133	return range_end - *range_start;
134	}
135
136	static void ifs_clear_range_dirty(struct folio *folio,
137	struct iomap_folio_state *ifs, size_t off, size_t len)
138	{
139	struct inode *inode = folio->mapping->host;
140	unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
141	unsigned int first_blk = (off >> inode->i_blkbits);
142	unsigned int last_blk = (off + len - 1) >> inode->i_blkbits;
143	unsigned int nr_blks = last_blk - first_blk + 1;
144	unsigned long flags;
145
146	spin_lock_irqsave(&ifs->state_lock, flags);
147	bitmap_clear(map: ifs->state, start: first_blk + blks_per_folio, nbits: nr_blks);
148	spin_unlock_irqrestore(lock: &ifs->state_lock, flags);
149	}
150
151	static void iomap_clear_range_dirty(struct folio *folio, size_t off, size_t len)
152	{
153	struct iomap_folio_state *ifs = folio->private;
154
155	if (ifs)
156	ifs_clear_range_dirty(folio, ifs, off, len);
157	}
158
159	static void ifs_set_range_dirty(struct folio *folio,
160	struct iomap_folio_state *ifs, size_t off, size_t len)
161	{
162	struct inode *inode = folio->mapping->host;
163	unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
164	unsigned int first_blk = (off >> inode->i_blkbits);
165	unsigned int last_blk = (off + len - 1) >> inode->i_blkbits;
166	unsigned int nr_blks = last_blk - first_blk + 1;
167	unsigned long flags;
168
169	spin_lock_irqsave(&ifs->state_lock, flags);
170	bitmap_set(map: ifs->state, start: first_blk + blks_per_folio, nbits: nr_blks);
171	spin_unlock_irqrestore(lock: &ifs->state_lock, flags);
172	}
173
174	static void iomap_set_range_dirty(struct folio *folio, size_t off, size_t len)
175	{
176	struct iomap_folio_state *ifs = folio->private;
177
178	if (ifs)
179	ifs_set_range_dirty(folio, ifs, off, len);
180	}
181
182	static struct iomap_folio_state *ifs_alloc(struct inode *inode,
183	struct folio *folio, unsigned int flags)
184	{
185	struct iomap_folio_state *ifs = folio->private;
186	unsigned int nr_blocks = i_blocks_per_folio(inode, folio);
187	gfp_t gfp;
188
189	if (ifs || nr_blocks <= 1)
190	return ifs;
191
192	if (flags & IOMAP_NOWAIT)
193	gfp = GFP_NOWAIT;
194	else
195	gfp = GFP_NOFS | __GFP_NOFAIL;
196
197	/*
198	* ifs->state tracks two sets of state flags when the
199	* filesystem block size is smaller than the folio size.
200	* The first state tracks per-block uptodate and the
201	* second tracks per-block dirty state.
202	*/
203	ifs = kzalloc(struct_size(ifs, state,
204	BITS_TO_LONGS(2 * nr_blocks)), flags: gfp);
205	if (!ifs)
206	return ifs;
207
208	spin_lock_init(&ifs->state_lock);
209	if (folio_test_uptodate(folio))
210	bitmap_set(map: ifs->state, start: 0, nbits: nr_blocks);
211	if (folio_test_dirty(folio))
212	bitmap_set(map: ifs->state, start: nr_blocks, nbits: nr_blocks);
213	folio_attach_private(folio, data: ifs);
214
215	return ifs;
216	}
217
218	static void ifs_free(struct folio *folio)
219	{
220	struct iomap_folio_state *ifs = folio_detach_private(folio);
221
222	if (!ifs)
223	return;
224	WARN_ON_ONCE(ifs->read_bytes_pending != 0);
225	WARN_ON_ONCE(atomic_read(&ifs->write_bytes_pending));
226	WARN_ON_ONCE(ifs_is_fully_uptodate(folio, ifs) !=
227	folio_test_uptodate(folio));
228	kfree(objp: ifs);
229	}
230
231	/*
232	* Calculate the range inside the folio that we actually need to read.
233	*/
234	static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
235	loff_t *pos, loff_t length, size_t *offp, size_t *lenp)
236	{
237	struct iomap_folio_state *ifs = folio->private;
238	loff_t orig_pos = *pos;
239	loff_t isize = i_size_read(inode);
240	unsigned block_bits = inode->i_blkbits;
241	unsigned block_size = (1 << block_bits);
242	size_t poff = offset_in_folio(folio, *pos);
243	size_t plen = min_t(loff_t, folio_size(folio) - poff, length);
244	unsigned first = poff >> block_bits;
245	unsigned last = (poff + plen - 1) >> block_bits;
246
247	/*
248	* If the block size is smaller than the page size, we need to check the
249	* per-block uptodate status and adjust the offset and length if needed
250	* to avoid reading in already uptodate ranges.
251	*/
252	if (ifs) {
253	unsigned int i;
254
255	/* move forward for each leading block marked uptodate */
256	for (i = first; i <= last; i++) {
257	if (!ifs_block_is_uptodate(ifs, block: i))
258	break;
259	*pos += block_size;
260	poff += block_size;
261	plen -= block_size;
262	first++;
263	}
264
265	/* truncate len if we find any trailing uptodate block(s) */
266	for ( ; i <= last; i++) {
267	if (ifs_block_is_uptodate(ifs, block: i)) {
268	plen -= (last - i + 1) * block_size;
269	last = i - 1;
270	break;
271	}
272	}
273	}
274
275	/*
276	* If the extent spans the block that contains the i_size, we need to
277	* handle both halves separately so that we properly zero data in the
278	* page cache for blocks that are entirely outside of i_size.
279	*/
280	if (orig_pos <= isize && orig_pos + length > isize) {
281	unsigned end = offset_in_folio(folio, isize - 1) >> block_bits;
282
283	if (first <= end && last > end)
284	plen -= (last - end) * block_size;
285	}
286
287	*offp = poff;
288	*lenp = plen;
289	}
290
291	static void iomap_finish_folio_read(struct folio *folio, size_t off,
292	size_t len, int error)
293	{
294	struct iomap_folio_state *ifs = folio->private;
295	bool uptodate = !error;
296	bool finished = true;
297
298	if (ifs) {
299	unsigned long flags;
300
301	spin_lock_irqsave(&ifs->state_lock, flags);
302	if (!error)
303	uptodate = ifs_set_range_uptodate(folio, ifs, off, len);
304	ifs->read_bytes_pending -= len;
305	finished = !ifs->read_bytes_pending;
306	spin_unlock_irqrestore(lock: &ifs->state_lock, flags);
307	}
308
309	if (error)
310	folio_set_error(folio);
311	if (finished)
312	folio_end_read(folio, success: uptodate);
313	}
314
315	static void iomap_read_end_io(struct bio *bio)
316	{
317	int error = blk_status_to_errno(status: bio->bi_status);
318	struct folio_iter fi;
319
320	bio_for_each_folio_all(fi, bio)
321	iomap_finish_folio_read(folio: fi.folio, off: fi.offset, len: fi.length, error);
322	bio_put(bio);
323	}
324
325	struct iomap_readpage_ctx {
326	struct folio *cur_folio;
327	bool cur_folio_in_bio;
328	struct bio *bio;
329	struct readahead_control *rac;
330	};
331
332	/**
333	* iomap_read_inline_data - copy inline data into the page cache
334	* @iter: iteration structure
335	* @folio: folio to copy to
336	*
337	* Copy the inline data in @iter into @folio and zero out the rest of the folio.
338	* Only a single IOMAP_INLINE extent is allowed at the end of each file.
339	* Returns zero for success to complete the read, or the usual negative errno.
340	*/
341	static int iomap_read_inline_data(const struct iomap_iter *iter,
342	struct folio *folio)
343	{
344	const struct iomap *iomap = iomap_iter_srcmap(i: iter);
345	size_t size = i_size_read(inode: iter->inode) - iomap->offset;
346	size_t offset = offset_in_folio(folio, iomap->offset);
347
348	if (folio_test_uptodate(folio))
349	return 0;
350
351	if (WARN_ON_ONCE(size > iomap->length))
352	return -EIO;
353	if (offset > 0)
354	ifs_alloc(inode: iter->inode, folio, flags: iter->flags);
355
356	folio_fill_tail(folio, offset, from: iomap->inline_data, len: size);
357	iomap_set_range_uptodate(folio, off: offset, len: folio_size(folio) - offset);
358	return 0;
359	}
360
361	static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
362	loff_t pos)
363	{
364	const struct iomap *srcmap = iomap_iter_srcmap(i: iter);
365
366	return srcmap->type != IOMAP_MAPPED ||
367	(srcmap->flags & IOMAP_F_NEW) ||
368	pos >= i_size_read(inode: iter->inode);
369	}
370
371	static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
372	struct iomap_readpage_ctx *ctx, loff_t offset)
373	{
374	const struct iomap *iomap = &iter->iomap;
375	loff_t pos = iter->pos + offset;
376	loff_t length = iomap_length(iter) - offset;
377	struct folio *folio = ctx->cur_folio;
378	struct iomap_folio_state *ifs;
379	loff_t orig_pos = pos;
380	size_t poff, plen;
381	sector_t sector;
382
383	if (iomap->type == IOMAP_INLINE)
384	return iomap_read_inline_data(iter, folio);
385
386	/* zero post-eof blocks as the page may be mapped */
387	ifs = ifs_alloc(inode: iter->inode, folio, flags: iter->flags);
388	iomap_adjust_read_range(inode: iter->inode, folio, pos: &pos, length, offp: &poff, lenp: &plen);
389	if (plen == 0)
390	goto done;
391
392	if (iomap_block_needs_zeroing(iter, pos)) {
393	folio_zero_range(folio, start: poff, length: plen);
394	iomap_set_range_uptodate(folio, off: poff, len: plen);
395	goto done;
396	}
397
398	ctx->cur_folio_in_bio = true;
399	if (ifs) {
400	spin_lock_irq(lock: &ifs->state_lock);
401	ifs->read_bytes_pending += plen;
402	spin_unlock_irq(lock: &ifs->state_lock);
403	}
404
405	sector = iomap_sector(iomap, pos);
406	if (!ctx->bio ||
407	bio_end_sector(ctx->bio) != sector ||
408	!bio_add_folio(bio: ctx->bio, folio, len: plen, off: poff)) {
409	gfp_t gfp = mapping_gfp_constraint(mapping: folio->mapping, GFP_KERNEL);
410	gfp_t orig_gfp = gfp;
411	unsigned int nr_vecs = DIV_ROUND_UP(length, PAGE_SIZE);
412
413	if (ctx->bio)
414	submit_bio(bio: ctx->bio);
415
416	if (ctx->rac) /* same as readahead_gfp_mask */
417	gfp |= __GFP_NORETRY | __GFP_NOWARN;
418	ctx->bio = bio_alloc(bdev: iomap->bdev, nr_vecs: bio_max_segs(nr_segs: nr_vecs),
419	opf: REQ_OP_READ, gfp_mask: gfp);
420	/*
421	* If the bio_alloc fails, try it again for a single page to
422	* avoid having to deal with partial page reads. This emulates
423	* what do_mpage_read_folio does.
424	*/
425	if (!ctx->bio) {
426	ctx->bio = bio_alloc(bdev: iomap->bdev, nr_vecs: 1, opf: REQ_OP_READ,
427	gfp_mask: orig_gfp);
428	}
429	if (ctx->rac)
430	ctx->bio->bi_opf |= REQ_RAHEAD;
431	ctx->bio->bi_iter.bi_sector = sector;
432	ctx->bio->bi_end_io = iomap_read_end_io;
433	bio_add_folio_nofail(bio: ctx->bio, folio, len: plen, off: poff);
434	}
435
436	done:
437	/*
438	* Move the caller beyond our range so that it keeps making progress.
439	* For that, we have to include any leading non-uptodate ranges, but
440	* we can skip trailing ones as they will be handled in the next
441	* iteration.
442	*/
443	return pos - orig_pos + plen;
444	}
445
446	int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
447	{
448	struct iomap_iter iter = {
449	.inode = folio->mapping->host,
450	.pos = folio_pos(folio),
451	.len = folio_size(folio),
452	};
453	struct iomap_readpage_ctx ctx = {
454	.cur_folio = folio,
455	};
456	int ret;
457
458	trace_iomap_readpage(inode: iter.inode, nr_pages: 1);
459
460	while ((ret = iomap_iter(iter: &iter, ops)) > 0)
461	iter.processed = iomap_readpage_iter(iter: &iter, ctx: &ctx, offset: 0);
462
463	if (ret < 0)
464	folio_set_error(folio);
465
466	if (ctx.bio) {
467	submit_bio(bio: ctx.bio);
468	WARN_ON_ONCE(!ctx.cur_folio_in_bio);
469	} else {
470	WARN_ON_ONCE(ctx.cur_folio_in_bio);
471	folio_unlock(folio);
472	}
473
474	/*
475	* Just like mpage_readahead and block_read_full_folio, we always
476	* return 0 and just set the folio error flag on errors. This
477	* should be cleaned up throughout the stack eventually.
478	*/
479	return 0;
480	}
481	EXPORT_SYMBOL_GPL(iomap_read_folio);
482
483	static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
484	struct iomap_readpage_ctx *ctx)
485	{
486	loff_t length = iomap_length(iter);
487	loff_t done, ret;
488
489	for (done = 0; done < length; done += ret) {
490	if (ctx->cur_folio &&
491	offset_in_folio(ctx->cur_folio, iter->pos + done) == 0) {
492	if (!ctx->cur_folio_in_bio)
493	folio_unlock(folio: ctx->cur_folio);
494	ctx->cur_folio = NULL;
495	}
496	if (!ctx->cur_folio) {
497	ctx->cur_folio = readahead_folio(ractl: ctx->rac);
498	ctx->cur_folio_in_bio = false;
499	}
500	ret = iomap_readpage_iter(iter, ctx, offset: done);
501	if (ret <= 0)
502	return ret;
503	}
504
505	return done;
506	}
507
508	/**
509	* iomap_readahead - Attempt to read pages from a file.
510	* @rac: Describes the pages to be read.
511	* @ops: The operations vector for the filesystem.
512	*
513	* This function is for filesystems to call to implement their readahead
514	* address_space operation.
515	*
516	* Context: The @ops callbacks may submit I/O (eg to read the addresses of
517	* blocks from disc), and may wait for it. The caller may be trying to
518	* access a different page, and so sleeping excessively should be avoided.
519	* It may allocate memory, but should avoid costly allocations. This
520	* function is called with memalloc_nofs set, so allocations will not cause
521	* the filesystem to be reentered.
522	*/
523	void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
524	{
525	struct iomap_iter iter = {
526	.inode = rac->mapping->host,
527	.pos = readahead_pos(rac),
528	.len = readahead_length(rac),
529	};
530	struct iomap_readpage_ctx ctx = {
531	.rac = rac,
532	};
533
534	trace_iomap_readahead(inode: rac->mapping->host, nr_pages: readahead_count(rac));
535
536	while (iomap_iter(iter: &iter, ops) > 0)
537	iter.processed = iomap_readahead_iter(iter: &iter, ctx: &ctx);
538
539	if (ctx.bio)
540	submit_bio(bio: ctx.bio);
541	if (ctx.cur_folio) {
542	if (!ctx.cur_folio_in_bio)
543	folio_unlock(folio: ctx.cur_folio);
544	}
545	}
546	EXPORT_SYMBOL_GPL(iomap_readahead);
547
548	/*
549	* iomap_is_partially_uptodate checks whether blocks within a folio are
550	* uptodate or not.
551	*
552	* Returns true if all blocks which correspond to the specified part
553	* of the folio are uptodate.
554	*/
555	bool iomap_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
556	{
557	struct iomap_folio_state *ifs = folio->private;
558	struct inode *inode = folio->mapping->host;
559	unsigned first, last, i;
560
561	if (!ifs)
562	return false;
563
564	/* Caller's range may extend past the end of this folio */
565	count = min(folio_size(folio) - from, count);
566
567	/* First and last blocks in range within folio */
568	first = from >> inode->i_blkbits;
569	last = (from + count - 1) >> inode->i_blkbits;
570
571	for (i = first; i <= last; i++)
572	if (!ifs_block_is_uptodate(ifs, block: i))
573	return false;
574	return true;
575	}
576	EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate);
577
578	/**
579	* iomap_get_folio - get a folio reference for writing
580	* @iter: iteration structure
581	* @pos: start offset of write
582	* @len: Suggested size of folio to create.
583	*
584	* Returns a locked reference to the folio at @pos, or an error pointer if the
585	* folio could not be obtained.
586	*/
587	struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len)
588	{
589	fgf_t fgp = FGP_WRITEBEGIN | FGP_NOFS;
590
591	if (iter->flags & IOMAP_NOWAIT)
592	fgp |= FGP_NOWAIT;
593	fgp |= fgf_set_order(size: len);
594
595	return __filemap_get_folio(mapping: iter->inode->i_mapping, index: pos >> PAGE_SHIFT,
596	fgp_flags: fgp, gfp: mapping_gfp_mask(mapping: iter->inode->i_mapping));
597	}
598	EXPORT_SYMBOL_GPL(iomap_get_folio);
599
600	bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags)
601	{
602	trace_iomap_release_folio(inode: folio->mapping->host, off: folio_pos(folio),
603	len: folio_size(folio));
604
605	/*
606	* If the folio is dirty, we refuse to release our metadata because
607	* it may be partially dirty. Once we track per-block dirty state,
608	* we can release the metadata if every block is dirty.
609	*/
610	if (folio_test_dirty(folio))
611	return false;
612	ifs_free(folio);
613	return true;
614	}
615	EXPORT_SYMBOL_GPL(iomap_release_folio);
616
617	void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len)
618	{
619	trace_iomap_invalidate_folio(inode: folio->mapping->host,
620	off: folio_pos(folio) + offset, len);
621
622	/*
623	* If we're invalidating the entire folio, clear the dirty state
624	* from it and release it to avoid unnecessary buildup of the LRU.
625	*/
626	if (offset == 0 && len == folio_size(folio)) {
627	WARN_ON_ONCE(folio_test_writeback(folio));
628	folio_cancel_dirty(folio);
629	ifs_free(folio);
630	}
631	}
632	EXPORT_SYMBOL_GPL(iomap_invalidate_folio);
633
634	bool iomap_dirty_folio(struct address_space *mapping, struct folio *folio)
635	{
636	struct inode *inode = mapping->host;
637	size_t len = folio_size(folio);
638
639	ifs_alloc(inode, folio, flags: 0);
640	iomap_set_range_dirty(folio, off: 0, len);
641	return filemap_dirty_folio(mapping, folio);
642	}
643	EXPORT_SYMBOL_GPL(iomap_dirty_folio);
644
645	static void
646	iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
647	{
648	loff_t i_size = i_size_read(inode);
649
650	/*
651	* Only truncate newly allocated pages beyoned EOF, even if the
652	* write started inside the existing inode size.
653	*/
654	if (pos + len > i_size)
655	truncate_pagecache_range(inode, max(pos, i_size),
656	end: pos + len - 1);
657	}
658
659	static int iomap_read_folio_sync(loff_t block_start, struct folio *folio,
660	size_t poff, size_t plen, const struct iomap *iomap)
661	{
662	struct bio_vec bvec;
663	struct bio bio;
664
665	bio_init(bio: &bio, bdev: iomap->bdev, table: &bvec, max_vecs: 1, opf: REQ_OP_READ);
666	bio.bi_iter.bi_sector = iomap_sector(iomap, pos: block_start);
667	bio_add_folio_nofail(bio: &bio, folio, len: plen, off: poff);
668	return submit_bio_wait(bio: &bio);
669	}
670
671	static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
672	size_t len, struct folio *folio)
673	{
674	const struct iomap *srcmap = iomap_iter_srcmap(i: iter);
675	struct iomap_folio_state *ifs;
676	loff_t block_size = i_blocksize(node: iter->inode);
677	loff_t block_start = round_down(pos, block_size);
678	loff_t block_end = round_up(pos + len, block_size);
679	unsigned int nr_blocks = i_blocks_per_folio(inode: iter->inode, folio);
680	size_t from = offset_in_folio(folio, pos), to = from + len;
681	size_t poff, plen;
682
683	/*
684	* If the write or zeroing completely overlaps the current folio, then
685	* entire folio will be dirtied so there is no need for
686	* per-block state tracking structures to be attached to this folio.
687	* For the unshare case, we must read in the ondisk contents because we
688	* are not changing pagecache contents.
689	*/
690	if (!(iter->flags & IOMAP_UNSHARE) && pos <= folio_pos(folio) &&
691	pos + len >= folio_pos(folio) + folio_size(folio))
692	return 0;
693
694	ifs = ifs_alloc(inode: iter->inode, folio, flags: iter->flags);
695	if ((iter->flags & IOMAP_NOWAIT) && !ifs && nr_blocks > 1)
696	return -EAGAIN;
697
698	if (folio_test_uptodate(folio))
699	return 0;
700	folio_clear_error(folio);
701
702	do {
703	iomap_adjust_read_range(inode: iter->inode, folio, pos: &block_start,
704	length: block_end - block_start, offp: &poff, lenp: &plen);
705	if (plen == 0)
706	break;
707
708	if (!(iter->flags & IOMAP_UNSHARE) &&
709	(from <= poff || from >= poff + plen) &&
710	(to <= poff || to >= poff + plen))
711	continue;
712
713	if (iomap_block_needs_zeroing(iter, pos: block_start)) {
714	if (WARN_ON_ONCE(iter->flags & IOMAP_UNSHARE))
715	return -EIO;
716	folio_zero_segments(folio, start1: poff, xend1: from, start2: to, xend2: poff + plen);
717	} else {
718	int status;
719
720	if (iter->flags & IOMAP_NOWAIT)
721	return -EAGAIN;
722
723	status = iomap_read_folio_sync(block_start, folio,
724	poff, plen, iomap: srcmap);
725	if (status)
726	return status;
727	}
728	iomap_set_range_uptodate(folio, off: poff, len: plen);
729	} while ((block_start += plen) < block_end);
730
731	return 0;
732	}
733
734	static struct folio *__iomap_get_folio(struct iomap_iter *iter, loff_t pos,
735	size_t len)
736	{
737	const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
738
739	if (folio_ops && folio_ops->get_folio)
740	return folio_ops->get_folio(iter, pos, len);
741	else
742	return iomap_get_folio(iter, pos, len);
743	}
744
745	static void __iomap_put_folio(struct iomap_iter *iter, loff_t pos, size_t ret,
746	struct folio *folio)
747	{
748	const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
749
750	if (folio_ops && folio_ops->put_folio) {
751	folio_ops->put_folio(iter->inode, pos, ret, folio);
752	} else {
753	folio_unlock(folio);
754	folio_put(folio);
755	}
756	}
757
758	static int iomap_write_begin_inline(const struct iomap_iter *iter,
759	struct folio *folio)
760	{
761	/* needs more work for the tailpacking case; disable for now */
762	if (WARN_ON_ONCE(iomap_iter_srcmap(iter)->offset != 0))
763	return -EIO;
764	return iomap_read_inline_data(iter, folio);
765	}
766
767	static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
768	size_t len, struct folio **foliop)
769	{
770	const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
771	const struct iomap *srcmap = iomap_iter_srcmap(i: iter);
772	struct folio *folio;
773	int status = 0;
774
775	BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
776	if (srcmap != &iter->iomap)
777	BUG_ON(pos + len > srcmap->offset + srcmap->length);
778
779	if (fatal_signal_pending(current))
780	return -EINTR;
781
782	if (!mapping_large_folio_support(mapping: iter->inode->i_mapping))
783	len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos));
784
785	folio = __iomap_get_folio(iter, pos, len);
786	if (IS_ERR(ptr: folio))
787	return PTR_ERR(ptr: folio);
788
789	/*
790	* Now we have a locked folio, before we do anything with it we need to
791	* check that the iomap we have cached is not stale. The inode extent
792	* mapping can change due to concurrent IO in flight (e.g.
793	* IOMAP_UNWRITTEN state can change and memory reclaim could have
794	* reclaimed a previously partially written page at this index after IO
795	* completion before this write reaches this file offset) and hence we
796	* could do the wrong thing here (zero a page range incorrectly or fail
797	* to zero) and corrupt data.
798	*/
799	if (folio_ops && folio_ops->iomap_valid) {
800	bool iomap_valid = folio_ops->iomap_valid(iter->inode,
801	&iter->iomap);
802	if (!iomap_valid) {
803	iter->iomap.flags |= IOMAP_F_STALE;
804	status = 0;
805	goto out_unlock;
806	}
807	}
808
809	if (pos + len > folio_pos(folio) + folio_size(folio))
810	len = folio_pos(folio) + folio_size(folio) - pos;
811
812	if (srcmap->type == IOMAP_INLINE)
813	status = iomap_write_begin_inline(iter, folio);
814	else if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
815	status = __block_write_begin_int(folio, pos, len, NULL, iomap: srcmap);
816	else
817	status = __iomap_write_begin(iter, pos, len, folio);
818
819	if (unlikely(status))
820	goto out_unlock;
821
822	*foliop = folio;
823	return 0;
824
825	out_unlock:
826	__iomap_put_folio(iter, pos, ret: 0, folio);
827	iomap_write_failed(inode: iter->inode, pos, len);
828
829	return status;
830	}
831
832	static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
833	size_t copied, struct folio *folio)
834	{
835	flush_dcache_folio(folio);
836
837	/*
838	* The blocks that were entirely written will now be uptodate, so we
839	* don't have to worry about a read_folio reading them and overwriting a
840	* partial write. However, if we've encountered a short write and only
841	* partially written into a block, it will not be marked uptodate, so a
842	* read_folio might come in and destroy our partial write.
843	*
844	* Do the simplest thing and just treat any short write to a
845	* non-uptodate page as a zero-length write, and force the caller to
846	* redo the whole thing.
847	*/
848	if (unlikely(copied < len && !folio_test_uptodate(folio)))
849	return 0;
850	iomap_set_range_uptodate(folio, offset_in_folio(folio, pos), len);
851	iomap_set_range_dirty(folio, offset_in_folio(folio, pos), len: copied);
852	filemap_dirty_folio(mapping: inode->i_mapping, folio);
853	return copied;
854	}
855
856	static size_t iomap_write_end_inline(const struct iomap_iter *iter,
857	struct folio *folio, loff_t pos, size_t copied)
858	{
859	const struct iomap *iomap = &iter->iomap;
860	void *addr;
861
862	WARN_ON_ONCE(!folio_test_uptodate(folio));
863	BUG_ON(!iomap_inline_data_valid(iomap));
864
865	flush_dcache_folio(folio);
866	addr = kmap_local_folio(folio, offset: pos);
867	memcpy(iomap_inline_data(iomap, pos), addr, copied);
868	kunmap_local(addr);
869
870	mark_inode_dirty(inode: iter->inode);
871	return copied;
872	}
873
874	/* Returns the number of bytes copied. May be 0. Cannot be an errno. */
875	static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
876	size_t copied, struct folio *folio)
877	{
878	const struct iomap *srcmap = iomap_iter_srcmap(i: iter);
879	loff_t old_size = iter->inode->i_size;
880	size_t ret;
881
882	if (srcmap->type == IOMAP_INLINE) {
883	ret = iomap_write_end_inline(iter, folio, pos, copied);
884	} else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
885	ret = block_write_end(NULL, iter->inode->i_mapping, pos, len,
886	copied, &folio->page, NULL);
887	} else {
888	ret = __iomap_write_end(inode: iter->inode, pos, len, copied, folio);
889	}
890
891	/*
892	* Update the in-memory inode size after copying the data into the page
893	* cache. It's up to the file system to write the updated size to disk,
894	* preferably after I/O completion so that no stale data is exposed.
895	*/
896	if (pos + ret > old_size) {
897	i_size_write(inode: iter->inode, i_size: pos + ret);
898	iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
899	}
900	__iomap_put_folio(iter, pos, ret, folio);
901
902	if (old_size < pos)
903	pagecache_isize_extended(inode: iter->inode, from: old_size, to: pos);
904	if (ret < len)
905	iomap_write_failed(inode: iter->inode, pos: pos + ret, len: len - ret);
906	return ret;
907	}
908
909	static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
910	{
911	loff_t length = iomap_length(iter);
912	size_t chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
913	loff_t pos = iter->pos;
914	ssize_t written = 0;
915	long status = 0;
916	struct address_space *mapping = iter->inode->i_mapping;
917	unsigned int bdp_flags = (iter->flags & IOMAP_NOWAIT) ? BDP_ASYNC : 0;
918
919	do {
920	struct folio *folio;
921	size_t offset; /* Offset into folio */
922	size_t bytes; /* Bytes to write to folio */
923	size_t copied; /* Bytes copied from user */
924
925	bytes = iov_iter_count(i);
926	retry:
927	offset = pos & (chunk - 1);
928	bytes = min(chunk - offset, bytes);
929	status = balance_dirty_pages_ratelimited_flags(mapping,
930	flags: bdp_flags);
931	if (unlikely(status))
932	break;
933
934	if (bytes > length)
935	bytes = length;
936
937	/*
938	* Bring in the user page that we'll copy from _first_.
939	* Otherwise there's a nasty deadlock on copying from the
940	* same page as we're writing to, without it being marked
941	* up-to-date.
942	*
943	* For async buffered writes the assumption is that the user
944	* page has already been faulted in. This can be optimized by
945	* faulting the user page.
946	*/
947	if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
948	status = -EFAULT;
949	break;
950	}
951
952	status = iomap_write_begin(iter, pos, len: bytes, foliop: &folio);
953	if (unlikely(status))
954	break;
955	if (iter->iomap.flags & IOMAP_F_STALE)
956	break;
957
958	offset = offset_in_folio(folio, pos);
959	if (bytes > folio_size(folio) - offset)
960	bytes = folio_size(folio) - offset;
961
962	if (mapping_writably_mapped(mapping))
963	flush_dcache_folio(folio);
964
965	copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
966	status = iomap_write_end(iter, pos, len: bytes, copied, folio);
967
968	if (unlikely(copied != status))
969	iov_iter_revert(i, bytes: copied - status);
970
971	cond_resched();
972	if (unlikely(status == 0)) {
973	/*
974	* A short copy made iomap_write_end() reject the
975	* thing entirely. Might be memory poisoning
976	* halfway through, might be a race with munmap,
977	* might be severe memory pressure.
978	*/
979	if (chunk > PAGE_SIZE)
980	chunk /= 2;
981	if (copied) {
982	bytes = copied;
983	goto retry;
984	}
985	} else {
986	pos += status;
987	written += status;
988	length -= status;
989	}
990	} while (iov_iter_count(i) && length);
991
992	if (status == -EAGAIN) {
993	iov_iter_revert(i, bytes: written);
994	return -EAGAIN;
995	}
996	return written ? written : status;
997	}
998
999	ssize_t
1000	iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
1001	const struct iomap_ops *ops)
1002	{
1003	struct iomap_iter iter = {
1004	.inode = iocb->ki_filp->f_mapping->host,
1005	.pos = iocb->ki_pos,
1006	.len = iov_iter_count(i),
1007	.flags = IOMAP_WRITE,
1008	};
1009	ssize_t ret;
1010
1011	if (iocb->ki_flags & IOCB_NOWAIT)
1012	iter.flags |= IOMAP_NOWAIT;
1013
1014	while ((ret = iomap_iter(iter: &iter, ops)) > 0)
1015	iter.processed = iomap_write_iter(iter: &iter, i);
1016
1017	if (unlikely(iter.pos == iocb->ki_pos))
1018	return ret;
1019	ret = iter.pos - iocb->ki_pos;
1020	iocb->ki_pos = iter.pos;
1021	return ret;
1022	}
1023	EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
1024
1025	static int iomap_write_delalloc_ifs_punch(struct inode *inode,
1026	struct folio *folio, loff_t start_byte, loff_t end_byte,
1027	iomap_punch_t punch)
1028	{
1029	unsigned int first_blk, last_blk, i;
1030	loff_t last_byte;
1031	u8 blkbits = inode->i_blkbits;
1032	struct iomap_folio_state *ifs;
1033	int ret = 0;
1034
1035	/*
1036	* When we have per-block dirty tracking, there can be
1037	* blocks within a folio which are marked uptodate
1038	* but not dirty. In that case it is necessary to punch
1039	* out such blocks to avoid leaking any delalloc blocks.
1040	*/
1041	ifs = folio->private;
1042	if (!ifs)
1043	return ret;
1044
1045	last_byte = min_t(loff_t, end_byte - 1,
1046	folio_pos(folio) + folio_size(folio) - 1);
1047	first_blk = offset_in_folio(folio, start_byte) >> blkbits;
1048	last_blk = offset_in_folio(folio, last_byte) >> blkbits;
1049	for (i = first_blk; i <= last_blk; i++) {
1050	if (!ifs_block_is_dirty(folio, ifs, block: i)) {
1051	ret = punch(inode, folio_pos(folio) + (i << blkbits),
1052	1 << blkbits);
1053	if (ret)
1054	return ret;
1055	}
1056	}
1057
1058	return ret;
1059	}
1060
1061
1062	static int iomap_write_delalloc_punch(struct inode *inode, struct folio *folio,
1063	loff_t *punch_start_byte, loff_t start_byte, loff_t end_byte,
1064	iomap_punch_t punch)
1065	{
1066	int ret = 0;
1067
1068	if (!folio_test_dirty(folio))
1069	return ret;
1070
1071	/* if dirty, punch up to offset */
1072	if (start_byte > *punch_start_byte) {
1073	ret = punch(inode, *punch_start_byte,
1074	start_byte - *punch_start_byte);
1075	if (ret)
1076	return ret;
1077	}
1078
1079	/* Punch non-dirty blocks within folio */
1080	ret = iomap_write_delalloc_ifs_punch(inode, folio, start_byte,
1081	end_byte, punch);
1082	if (ret)
1083	return ret;
1084
1085	/*
1086	* Make sure the next punch start is correctly bound to
1087	* the end of this data range, not the end of the folio.
1088	*/
1089	*punch_start_byte = min_t(loff_t, end_byte,
1090	folio_pos(folio) + folio_size(folio));
1091
1092	return ret;
1093	}
1094
1095	/*
1096	* Scan the data range passed to us for dirty page cache folios. If we find a
1097	* dirty folio, punch out the preceding range and update the offset from which
1098	* the next punch will start from.
1099	*
1100	* We can punch out storage reservations under clean pages because they either
1101	* contain data that has been written back - in which case the delalloc punch
1102	* over that range is a no-op - or they have been read faults in which case they
1103	* contain zeroes and we can remove the delalloc backing range and any new
1104	* writes to those pages will do the normal hole filling operation...
1105	*
1106	* This makes the logic simple: we only need to keep the delalloc extents only
1107	* over the dirty ranges of the page cache.
1108	*
1109	* This function uses [start_byte, end_byte) intervals (i.e. open ended) to
1110	* simplify range iterations.
1111	*/
1112	static int iomap_write_delalloc_scan(struct inode *inode,
1113	loff_t *punch_start_byte, loff_t start_byte, loff_t end_byte,
1114	iomap_punch_t punch)
1115	{
1116	while (start_byte < end_byte) {
1117	struct folio *folio;
1118	int ret;
1119
1120	/* grab locked page */
1121	folio = filemap_lock_folio(mapping: inode->i_mapping,
1122	index: start_byte >> PAGE_SHIFT);
1123	if (IS_ERR(ptr: folio)) {
1124	start_byte = ALIGN_DOWN(start_byte, PAGE_SIZE) +
1125	PAGE_SIZE;
1126	continue;
1127	}
1128
1129	ret = iomap_write_delalloc_punch(inode, folio, punch_start_byte,
1130	start_byte, end_byte, punch);
1131	if (ret) {
1132	folio_unlock(folio);
1133	folio_put(folio);
1134	return ret;
1135	}
1136
1137	/* move offset to start of next folio in range */
1138	start_byte = folio_next_index(folio) << PAGE_SHIFT;
1139	folio_unlock(folio);
1140	folio_put(folio);
1141	}
1142	return 0;
1143	}
1144
1145	/*
1146	* Punch out all the delalloc blocks in the range given except for those that
1147	* have dirty data still pending in the page cache - those are going to be
1148	* written and so must still retain the delalloc backing for writeback.
1149	*
1150	* As we are scanning the page cache for data, we don't need to reimplement the
1151	* wheel - mapping_seek_hole_data() does exactly what we need to identify the
1152	* start and end of data ranges correctly even for sub-folio block sizes. This
1153	* byte range based iteration is especially convenient because it means we
1154	* don't have to care about variable size folios, nor where the start or end of
1155	* the data range lies within a folio, if they lie within the same folio or even
1156	* if there are multiple discontiguous data ranges within the folio.
1157	*
1158	* It should be noted that mapping_seek_hole_data() is not aware of EOF, and so
1159	* can return data ranges that exist in the cache beyond EOF. e.g. a page fault
1160	* spanning EOF will initialise the post-EOF data to zeroes and mark it up to
1161	* date. A write page fault can then mark it dirty. If we then fail a write()
1162	* beyond EOF into that up to date cached range, we allocate a delalloc block
1163	* beyond EOF and then have to punch it out. Because the range is up to date,
1164	* mapping_seek_hole_data() will return it, and we will skip the punch because
1165	* the folio is dirty. THis is incorrect - we always need to punch out delalloc
1166	* beyond EOF in this case as writeback will never write back and covert that
1167	* delalloc block beyond EOF. Hence we limit the cached data scan range to EOF,
1168	* resulting in always punching out the range from the EOF to the end of the
1169	* range the iomap spans.
1170	*
1171	* Intervals are of the form [start_byte, end_byte) (i.e. open ended) because it
1172	* matches the intervals returned by mapping_seek_hole_data(). i.e. SEEK_DATA
1173	* returns the start of a data range (start_byte), and SEEK_HOLE(start_byte)
1174	* returns the end of the data range (data_end). Using closed intervals would
1175	* require sprinkling this code with magic "+ 1" and "- 1" arithmetic and expose
1176	* the code to subtle off-by-one bugs....
1177	*/
1178	static int iomap_write_delalloc_release(struct inode *inode,
1179	loff_t start_byte, loff_t end_byte, iomap_punch_t punch)
1180	{
1181	loff_t punch_start_byte = start_byte;
1182	loff_t scan_end_byte = min(i_size_read(inode), end_byte);
1183	int error = 0;
1184
1185	/*
1186	* Lock the mapping to avoid races with page faults re-instantiating
1187	* folios and dirtying them via ->page_mkwrite whilst we walk the
1188	* cache and perform delalloc extent removal. Failing to do this can
1189	* leave dirty pages with no space reservation in the cache.
1190	*/
1191	filemap_invalidate_lock(mapping: inode->i_mapping);
1192	while (start_byte < scan_end_byte) {
1193	loff_t data_end;
1194
1195	start_byte = mapping_seek_hole_data(inode->i_mapping,
1196	start: start_byte, end: scan_end_byte, SEEK_DATA);
1197	/*
1198	* If there is no more data to scan, all that is left is to
1199	* punch out the remaining range.
1200	*/
1201	if (start_byte == -ENXIO || start_byte == scan_end_byte)
1202	break;
1203	if (start_byte < 0) {
1204	error = start_byte;
1205	goto out_unlock;
1206	}
1207	WARN_ON_ONCE(start_byte < punch_start_byte);
1208	WARN_ON_ONCE(start_byte > scan_end_byte);
1209
1210	/*
1211	* We find the end of this contiguous cached data range by
1212	* seeking from start_byte to the beginning of the next hole.
1213	*/
1214	data_end = mapping_seek_hole_data(inode->i_mapping, start: start_byte,
1215	end: scan_end_byte, SEEK_HOLE);
1216	if (data_end < 0) {
1217	error = data_end;
1218	goto out_unlock;
1219	}
1220	WARN_ON_ONCE(data_end <= start_byte);
1221	WARN_ON_ONCE(data_end > scan_end_byte);
1222
1223	error = iomap_write_delalloc_scan(inode, punch_start_byte: &punch_start_byte,
1224	start_byte, end_byte: data_end, punch);
1225	if (error)
1226	goto out_unlock;
1227
1228	/* The next data search starts at the end of this one. */
1229	start_byte = data_end;
1230	}
1231
1232	if (punch_start_byte < end_byte)
1233	error = punch(inode, punch_start_byte,
1234	end_byte - punch_start_byte);
1235	out_unlock:
1236	filemap_invalidate_unlock(mapping: inode->i_mapping);
1237	return error;
1238	}
1239
1240	/*
1241	* When a short write occurs, the filesystem may need to remove reserved space
1242	* that was allocated in ->iomap_begin from it's ->iomap_end method. For
1243	* filesystems that use delayed allocation, we need to punch out delalloc
1244	* extents from the range that are not dirty in the page cache. As the write can
1245	* race with page faults, there can be dirty pages over the delalloc extent
1246	* outside the range of a short write but still within the delalloc extent
1247	* allocated for this iomap.
1248	*
1249	* This function uses [start_byte, end_byte) intervals (i.e. open ended) to
1250	* simplify range iterations.
1251	*
1252	* The punch() callback *must* only punch delalloc extents in the range passed
1253	* to it. It must skip over all other types of extents in the range and leave
1254	* them completely unchanged. It must do this punch atomically with respect to
1255	* other extent modifications.
1256	*
1257	* The punch() callback may be called with a folio locked to prevent writeback
1258	* extent allocation racing at the edge of the range we are currently punching.
1259	* The locked folio may or may not cover the range being punched, so it is not
1260	* safe for the punch() callback to lock folios itself.
1261	*
1262	* Lock order is:
1263	*
1264	* inode->i_rwsem (shared or exclusive)
1265	* inode->i_mapping->invalidate_lock (exclusive)
1266	* folio_lock()
1267	* ->punch
1268	* internal filesystem allocation lock
1269	*/
1270	int iomap_file_buffered_write_punch_delalloc(struct inode *inode,
1271	struct iomap *iomap, loff_t pos, loff_t length,
1272	ssize_t written, iomap_punch_t punch)
1273	{
1274	loff_t start_byte;
1275	loff_t end_byte;
1276	unsigned int blocksize = i_blocksize(node: inode);
1277
1278	if (iomap->type != IOMAP_DELALLOC)
1279	return 0;
1280
1281	/* If we didn't reserve the blocks, we're not allowed to punch them. */
1282	if (!(iomap->flags & IOMAP_F_NEW))
1283	return 0;
1284
1285	/*
1286	* start_byte refers to the first unused block after a short write. If
1287	* nothing was written, round offset down to point at the first block in
1288	* the range.
1289	*/
1290	if (unlikely(!written))
1291	start_byte = round_down(pos, blocksize);
1292	else
1293	start_byte = round_up(pos + written, blocksize);
1294	end_byte = round_up(pos + length, blocksize);
1295
1296	/* Nothing to do if we've written the entire delalloc extent */
1297	if (start_byte >= end_byte)
1298	return 0;
1299
1300	return iomap_write_delalloc_release(inode, start_byte, end_byte,
1301	punch);
1302	}
1303	EXPORT_SYMBOL_GPL(iomap_file_buffered_write_punch_delalloc);
1304
1305	static loff_t iomap_unshare_iter(struct iomap_iter *iter)
1306	{
1307	struct iomap *iomap = &iter->iomap;
1308	const struct iomap *srcmap = iomap_iter_srcmap(i: iter);
1309	loff_t pos = iter->pos;
1310	loff_t length = iomap_length(iter);
1311	loff_t written = 0;
1312
1313	/* don't bother with blocks that are not shared to start with */
1314	if (!(iomap->flags & IOMAP_F_SHARED))
1315	return length;
1316	/* don't bother with holes or unwritten extents */
1317	if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
1318	return length;
1319
1320	do {
1321	struct folio *folio;
1322	int status;
1323	size_t offset;
1324	size_t bytes = min_t(u64, SIZE_MAX, length);
1325
1326	status = iomap_write_begin(iter, pos, len: bytes, foliop: &folio);
1327	if (unlikely(status))
1328	return status;
1329	if (iomap->flags & IOMAP_F_STALE)
1330	break;
1331
1332	offset = offset_in_folio(folio, pos);
1333	if (bytes > folio_size(folio) - offset)
1334	bytes = folio_size(folio) - offset;
1335
1336	bytes = iomap_write_end(iter, pos, len: bytes, copied: bytes, folio);
1337	if (WARN_ON_ONCE(bytes == 0))
1338	return -EIO;
1339
1340	cond_resched();
1341
1342	pos += bytes;
1343	written += bytes;
1344	length -= bytes;
1345
1346	balance_dirty_pages_ratelimited(mapping: iter->inode->i_mapping);
1347	} while (length > 0);
1348
1349	return written;
1350	}
1351
1352	int
1353	iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
1354	const struct iomap_ops *ops)
1355	{
1356	struct iomap_iter iter = {
1357	.inode = inode,
1358	.pos = pos,
1359	.len = len,
1360	.flags = IOMAP_WRITE | IOMAP_UNSHARE,
1361	};
1362	int ret;
1363
1364	while ((ret = iomap_iter(iter: &iter, ops)) > 0)
1365	iter.processed = iomap_unshare_iter(iter: &iter);
1366	return ret;
1367	}
1368	EXPORT_SYMBOL_GPL(iomap_file_unshare);
1369
1370	static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
1371	{
1372	const struct iomap *srcmap = iomap_iter_srcmap(i: iter);
1373	loff_t pos = iter->pos;
1374	loff_t length = iomap_length(iter);
1375	loff_t written = 0;
1376
1377	/* already zeroed? we're done. */
1378	if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
1379	return length;
1380
1381	do {
1382	struct folio *folio;
1383	int status;
1384	size_t offset;
1385	size_t bytes = min_t(u64, SIZE_MAX, length);
1386
1387	status = iomap_write_begin(iter, pos, len: bytes, foliop: &folio);
1388	if (status)
1389	return status;
1390	if (iter->iomap.flags & IOMAP_F_STALE)
1391	break;
1392
1393	offset = offset_in_folio(folio, pos);
1394	if (bytes > folio_size(folio) - offset)
1395	bytes = folio_size(folio) - offset;
1396
1397	folio_zero_range(folio, start: offset, length: bytes);
1398	folio_mark_accessed(folio);
1399
1400	bytes = iomap_write_end(iter, pos, len: bytes, copied: bytes, folio);
1401	if (WARN_ON_ONCE(bytes == 0))
1402	return -EIO;
1403
1404	pos += bytes;
1405	length -= bytes;
1406	written += bytes;
1407	} while (length > 0);
1408
1409	if (did_zero)
1410	*did_zero = true;
1411	return written;
1412	}
1413
1414	int
1415	iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
1416	const struct iomap_ops *ops)
1417	{
1418	struct iomap_iter iter = {
1419	.inode = inode,
1420	.pos = pos,
1421	.len = len,
1422	.flags = IOMAP_ZERO,
1423	};
1424	int ret;
1425
1426	while ((ret = iomap_iter(iter: &iter, ops)) > 0)
1427	iter.processed = iomap_zero_iter(iter: &iter, did_zero);
1428	return ret;
1429	}
1430	EXPORT_SYMBOL_GPL(iomap_zero_range);
1431
1432	int
1433	iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
1434	const struct iomap_ops *ops)
1435	{
1436	unsigned int blocksize = i_blocksize(node: inode);
1437	unsigned int off = pos & (blocksize - 1);
1438
1439	/* Block boundary? Nothing to do */
1440	if (!off)
1441	return 0;
1442	return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
1443	}
1444	EXPORT_SYMBOL_GPL(iomap_truncate_page);
1445
1446	static loff_t iomap_folio_mkwrite_iter(struct iomap_iter *iter,
1447	struct folio *folio)
1448	{
1449	loff_t length = iomap_length(iter);
1450	int ret;
1451
1452	if (iter->iomap.flags & IOMAP_F_BUFFER_HEAD) {
1453	ret = __block_write_begin_int(folio, pos: iter->pos, len: length, NULL,
1454	iomap: &iter->iomap);
1455	if (ret)
1456	return ret;
1457	block_commit_write(page: &folio->page, from: 0, to: length);
1458	} else {
1459	WARN_ON_ONCE(!folio_test_uptodate(folio));
1460	folio_mark_dirty(folio);
1461	}
1462
1463	return length;
1464	}
1465
1466	vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
1467	{
1468	struct iomap_iter iter = {
1469	.inode = file_inode(f: vmf->vma->vm_file),
1470	.flags = IOMAP_WRITE | IOMAP_FAULT,
1471	};
1472	struct folio *folio = page_folio(vmf->page);
1473	ssize_t ret;
1474
1475	folio_lock(folio);
1476	ret = folio_mkwrite_check_truncate(folio, inode: iter.inode);
1477	if (ret < 0)
1478	goto out_unlock;
1479	iter.pos = folio_pos(folio);
1480	iter.len = ret;
1481	while ((ret = iomap_iter(iter: &iter, ops)) > 0)
1482	iter.processed = iomap_folio_mkwrite_iter(iter: &iter, folio);
1483
1484	if (ret < 0)
1485	goto out_unlock;
1486	folio_wait_stable(folio);
1487	return VM_FAULT_LOCKED;
1488	out_unlock:
1489	folio_unlock(folio);
1490	return vmf_fs_error(err: ret);
1491	}
1492	EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
1493
1494	static void iomap_finish_folio_write(struct inode *inode, struct folio *folio,
1495	size_t len)
1496	{
1497	struct iomap_folio_state *ifs = folio->private;
1498
1499	WARN_ON_ONCE(i_blocks_per_folio(inode, folio) > 1 && !ifs);
1500	WARN_ON_ONCE(ifs && atomic_read(&ifs->write_bytes_pending) <= 0);
1501
1502	if (!ifs || atomic_sub_and_test(i: len, v: &ifs->write_bytes_pending))
1503	folio_end_writeback(folio);
1504	}
1505
1506	/*
1507	* We're now finished for good with this ioend structure. Update the page
1508	* state, release holds on bios, and finally free up memory. Do not use the
1509	* ioend after this.
1510	*/
1511	static u32
1512	iomap_finish_ioend(struct iomap_ioend *ioend, int error)
1513	{
1514	struct inode *inode = ioend->io_inode;
1515	struct bio *bio = &ioend->io_bio;
1516	struct folio_iter fi;
1517	u32 folio_count = 0;
1518
1519	if (error) {
1520	mapping_set_error(mapping: inode->i_mapping, error);
1521	if (!bio_flagged(bio, bit: BIO_QUIET)) {
1522	pr_err_ratelimited(
1523	"%s: writeback error on inode %lu, offset %lld, sector %llu",
1524	inode->i_sb->s_id, inode->i_ino,
1525	ioend->io_offset, ioend->io_sector);
1526	}
1527	}
1528
1529	/* walk all folios in bio, ending page IO on them */
1530	bio_for_each_folio_all(fi, bio) {
1531	if (error)
1532	folio_set_error(folio: fi.folio);
1533	iomap_finish_folio_write(inode, folio: fi.folio, len: fi.length);
1534	folio_count++;
1535	}
1536
1537	bio_put(bio); /* frees the ioend */
1538	return folio_count;
1539	}
1540
1541	/*
1542	* Ioend completion routine for merged bios. This can only be called from task
1543	* contexts as merged ioends can be of unbound length. Hence we have to break up
1544	* the writeback completions into manageable chunks to avoid long scheduler
1545	* holdoffs. We aim to keep scheduler holdoffs down below 10ms so that we get
1546	* good batch processing throughput without creating adverse scheduler latency
1547	* conditions.
1548	*/
1549	void
1550	iomap_finish_ioends(struct iomap_ioend *ioend, int error)
1551	{
1552	struct list_head tmp;
1553	u32 completions;
1554
1555	might_sleep();
1556
1557	list_replace_init(old: &ioend->io_list, new: &tmp);
1558	completions = iomap_finish_ioend(ioend, error);
1559
1560	while (!list_empty(head: &tmp)) {
1561	if (completions > IOEND_BATCH_SIZE * 8) {
1562	cond_resched();
1563	completions = 0;
1564	}
1565	ioend = list_first_entry(&tmp, struct iomap_ioend, io_list);
1566	list_del_init(entry: &ioend->io_list);
1567	completions += iomap_finish_ioend(ioend, error);
1568	}
1569	}
1570	EXPORT_SYMBOL_GPL(iomap_finish_ioends);
1571
1572	/*
1573	* We can merge two adjacent ioends if they have the same set of work to do.
1574	*/
1575	static bool
1576	iomap_ioend_can_merge(struct iomap_ioend *ioend, struct iomap_ioend *next)
1577	{
1578	if (ioend->io_bio.bi_status != next->io_bio.bi_status)
1579	return false;
1580	if ((ioend->io_flags & IOMAP_F_SHARED) ^
1581	(next->io_flags & IOMAP_F_SHARED))
1582	return false;
1583	if ((ioend->io_type == IOMAP_UNWRITTEN) ^
1584	(next->io_type == IOMAP_UNWRITTEN))
1585	return false;
1586	if (ioend->io_offset + ioend->io_size != next->io_offset)
1587	return false;
1588	/*
1589	* Do not merge physically discontiguous ioends. The filesystem
1590	* completion functions will have to iterate the physical
1591	* discontiguities even if we merge the ioends at a logical level, so
1592	* we don't gain anything by merging physical discontiguities here.
1593	*
1594	* We cannot use bio->bi_iter.bi_sector here as it is modified during
1595	* submission so does not point to the start sector of the bio at
1596	* completion.
1597	*/
1598	if (ioend->io_sector + (ioend->io_size >> 9) != next->io_sector)
1599	return false;
1600	return true;
1601	}
1602
1603	void
1604	iomap_ioend_try_merge(struct iomap_ioend *ioend, struct list_head *more_ioends)
1605	{
1606	struct iomap_ioend *next;
1607
1608	INIT_LIST_HEAD(list: &ioend->io_list);
1609
1610	while ((next = list_first_entry_or_null(more_ioends, struct iomap_ioend,
1611	io_list))) {
1612	if (!iomap_ioend_can_merge(ioend, next))
1613	break;
1614	list_move_tail(list: &next->io_list, head: &ioend->io_list);
1615	ioend->io_size += next->io_size;
1616	}
1617	}
1618	EXPORT_SYMBOL_GPL(iomap_ioend_try_merge);
1619
1620	static int
1621	iomap_ioend_compare(void *priv, const struct list_head *a,
1622	const struct list_head *b)
1623	{
1624	struct iomap_ioend *ia = container_of(a, struct iomap_ioend, io_list);
1625	struct iomap_ioend *ib = container_of(b, struct iomap_ioend, io_list);
1626
1627	if (ia->io_offset < ib->io_offset)
1628	return -1;
1629	if (ia->io_offset > ib->io_offset)
1630	return 1;
1631	return 0;
1632	}
1633
1634	void
1635	iomap_sort_ioends(struct list_head *ioend_list)
1636	{
1637	list_sort(NULL, head: ioend_list, cmp: iomap_ioend_compare);
1638	}
1639	EXPORT_SYMBOL_GPL(iomap_sort_ioends);
1640
1641	static void iomap_writepage_end_bio(struct bio *bio)
1642	{
1643	iomap_finish_ioend(ioend: iomap_ioend_from_bio(bio),
1644	error: blk_status_to_errno(status: bio->bi_status));
1645	}
1646
1647	/*
1648	* Submit the final bio for an ioend.
1649	*
1650	* If @error is non-zero, it means that we have a situation where some part of
1651	* the submission process has failed after we've marked pages for writeback.
1652	* We cannot cancel ioend directly in that case, so call the bio end I/O handler
1653	* with the error status here to run the normal I/O completion handler to clear
1654	* the writeback bit and let the file system proess the errors.
1655	*/
1656	static int iomap_submit_ioend(struct iomap_writepage_ctx *wpc, int error)
1657	{
1658	if (!wpc->ioend)
1659	return error;
1660
1661	/*
1662	* Let the file systems prepare the I/O submission and hook in an I/O
1663	* comletion handler. This also needs to happen in case after a
1664	* failure happened so that the file system end I/O handler gets called
1665	* to clean up.
1666	*/
1667	if (wpc->ops->prepare_ioend)
1668	error = wpc->ops->prepare_ioend(wpc->ioend, error);
1669
1670	if (error) {
1671	wpc->ioend->io_bio.bi_status = errno_to_blk_status(errno: error);
1672	bio_endio(&wpc->ioend->io_bio);
1673	} else {
1674	submit_bio(bio: &wpc->ioend->io_bio);
1675	}
1676
1677	wpc->ioend = NULL;
1678	return error;
1679	}
1680
1681	static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
1682	struct writeback_control *wbc, struct inode *inode, loff_t pos)
1683	{
1684	struct iomap_ioend *ioend;
1685	struct bio *bio;
1686
1687	bio = bio_alloc_bioset(bdev: wpc->iomap.bdev, BIO_MAX_VECS,
1688	opf: REQ_OP_WRITE | wbc_to_write_flags(wbc),
1689	GFP_NOFS, bs: &iomap_ioend_bioset);
1690	bio->bi_iter.bi_sector = iomap_sector(iomap: &wpc->iomap, pos);
1691	bio->bi_end_io = iomap_writepage_end_bio;
1692	wbc_init_bio(wbc, bio);
1693	bio->bi_write_hint = inode->i_write_hint;
1694
1695	ioend = iomap_ioend_from_bio(bio);
1696	INIT_LIST_HEAD(list: &ioend->io_list);
1697	ioend->io_type = wpc->iomap.type;
1698	ioend->io_flags = wpc->iomap.flags;
1699	ioend->io_inode = inode;
1700	ioend->io_size = 0;
1701	ioend->io_offset = pos;
1702	ioend->io_sector = bio->bi_iter.bi_sector;
1703
1704	wpc->nr_folios = 0;
1705	return ioend;
1706	}
1707
1708	static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t pos)
1709	{
1710	if ((wpc->iomap.flags & IOMAP_F_SHARED) !=
1711	(wpc->ioend->io_flags & IOMAP_F_SHARED))
1712	return false;
1713	if (wpc->iomap.type != wpc->ioend->io_type)
1714	return false;
1715	if (pos != wpc->ioend->io_offset + wpc->ioend->io_size)
1716	return false;
1717	if (iomap_sector(iomap: &wpc->iomap, pos) !=
1718	bio_end_sector(&wpc->ioend->io_bio))
1719	return false;
1720	/*
1721	* Limit ioend bio chain lengths to minimise IO completion latency. This
1722	* also prevents long tight loops ending page writeback on all the
1723	* folios in the ioend.
1724	*/
1725	if (wpc->nr_folios >= IOEND_BATCH_SIZE)
1726	return false;
1727	return true;
1728	}
1729
1730	/*
1731	* Test to see if we have an existing ioend structure that we could append to
1732	* first; otherwise finish off the current ioend and start another.
1733	*
1734	* If a new ioend is created and cached, the old ioend is submitted to the block
1735	* layer instantly. Batching optimisations are provided by higher level block
1736	* plugging.
1737	*
1738	* At the end of a writeback pass, there will be a cached ioend remaining on the
1739	* writepage context that the caller will need to submit.
1740	*/
1741	static int iomap_add_to_ioend(struct iomap_writepage_ctx *wpc,
1742	struct writeback_control *wbc, struct folio *folio,
1743	struct inode *inode, loff_t pos, unsigned len)
1744	{
1745	struct iomap_folio_state *ifs = folio->private;
1746	size_t poff = offset_in_folio(folio, pos);
1747	int error;
1748
1749	if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, pos)) {
1750	new_ioend:
1751	error = iomap_submit_ioend(wpc, error: 0);
1752	if (error)
1753	return error;
1754	wpc->ioend = iomap_alloc_ioend(wpc, wbc, inode, pos);
1755	}
1756
1757	if (!bio_add_folio(bio: &wpc->ioend->io_bio, folio, len, off: poff))
1758	goto new_ioend;
1759
1760	if (ifs)
1761	atomic_add(i: len, v: &ifs->write_bytes_pending);
1762	wpc->ioend->io_size += len;
1763	wbc_account_cgroup_owner(wbc, page: &folio->page, bytes: len);
1764	return 0;
1765	}
1766
1767	static int iomap_writepage_map_blocks(struct iomap_writepage_ctx *wpc,
1768	struct writeback_control *wbc, struct folio *folio,
1769	struct inode *inode, u64 pos, unsigned dirty_len,
1770	unsigned *count)
1771	{
1772	int error;
1773
1774	do {
1775	unsigned map_len;
1776
1777	error = wpc->ops->map_blocks(wpc, inode, pos, dirty_len);
1778	if (error)
1779	break;
1780	trace_iomap_writepage_map(inode, pos, dirty_len, iomap: &wpc->iomap);
1781
1782	map_len = min_t(u64, dirty_len,
1783	wpc->iomap.offset + wpc->iomap.length - pos);
1784	WARN_ON_ONCE(!folio->private && map_len < dirty_len);
1785
1786	switch (wpc->iomap.type) {
1787	case IOMAP_INLINE:
1788	WARN_ON_ONCE(1);
1789	error = -EIO;
1790	break;
1791	case IOMAP_HOLE:
1792	break;
1793	default:
1794	error = iomap_add_to_ioend(wpc, wbc, folio, inode, pos,
1795	len: map_len);
1796	if (!error)
1797	(*count)++;
1798	break;
1799	}
1800	dirty_len -= map_len;
1801	pos += map_len;
1802	} while (dirty_len && !error);
1803
1804	/*
1805	* We cannot cancel the ioend directly here on error. We may have
1806	* already set other pages under writeback and hence we have to run I/O
1807	* completion to mark the error state of the pages under writeback
1808	* appropriately.
1809	*
1810	* Just let the file system know what portion of the folio failed to
1811	* map.
1812	*/
1813	if (error && wpc->ops->discard_folio)
1814	wpc->ops->discard_folio(folio, pos);
1815	return error;
1816	}
1817
1818	/*
1819	* Check interaction of the folio with the file end.
1820	*
1821	* If the folio is entirely beyond i_size, return false. If it straddles
1822	* i_size, adjust end_pos and zero all data beyond i_size.
1823	*/
1824	static bool iomap_writepage_handle_eof(struct folio *folio, struct inode *inode,
1825	u64 *end_pos)
1826	{
1827	u64 isize = i_size_read(inode);
1828
1829	if (*end_pos > isize) {
1830	size_t poff = offset_in_folio(folio, isize);
1831	pgoff_t end_index = isize >> PAGE_SHIFT;
1832
1833	/*
1834	* If the folio is entirely ouside of i_size, skip it.
1835	*
1836	* This can happen due to a truncate operation that is in
1837	* progress and in that case truncate will finish it off once
1838	* we've dropped the folio lock.
1839	*
1840	* Note that the pgoff_t used for end_index is an unsigned long.
1841	* If the given offset is greater than 16TB on a 32-bit system,
1842	* then if we checked if the folio is fully outside i_size with
1843	* "if (folio->index >= end_index + 1)", "end_index + 1" would
1844	* overflow and evaluate to 0. Hence this folio would be
1845	* redirtied and written out repeatedly, which would result in
1846	* an infinite loop; the user program performing this operation
1847	* would hang. Instead, we can detect this situation by
1848	* checking if the folio is totally beyond i_size or if its
1849	* offset is just equal to the EOF.
1850	*/
1851	if (folio->index > end_index ||
1852	(folio->index == end_index && poff == 0))
1853	return false;
1854
1855	/*
1856	* The folio straddles i_size.
1857	*
1858	* It must be zeroed out on each and every writepage invocation
1859	* because it may be mmapped:
1860	*
1861	* A file is mapped in multiples of the page size. For a
1862	* file that is not a multiple of the page size, the
1863	* remaining memory is zeroed when mapped, and writes to that
1864	* region are not written out to the file.
1865	*
1866	* Also adjust the writeback range to skip all blocks entirely
1867	* beyond i_size.
1868	*/
1869	folio_zero_segment(folio, start: poff, xend: folio_size(folio));
1870	*end_pos = round_up(isize, i_blocksize(inode));
1871	}
1872
1873	return true;
1874	}
1875
1876	static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
1877	struct writeback_control *wbc, struct folio *folio)
1878	{
1879	struct iomap_folio_state *ifs = folio->private;
1880	struct inode *inode = folio->mapping->host;
1881	u64 pos = folio_pos(folio);
1882	u64 end_pos = pos + folio_size(folio);
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, off: pos, len: folio_size(folio));
1892
1893	if (!iomap_writepage_handle_eof(folio, inode, end_pos: &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, flags: 0);
1902	iomap_set_range_dirty(folio, off: 0, len: 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(v: &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	while ((rlen = iomap_find_dirty_range(folio, range_start: &pos, range_end: end_pos))) {
1925	error = iomap_writepage_map_blocks(wpc, wbc, folio, inode,
1926	pos, dirty_len: rlen, count: &count);
1927	if (error)
1928	break;
1929	pos += rlen;
1930	}
1931
1932	if (count)
1933	wpc->nr_folios++;
1934
1935	/*
1936	* We can have dirty bits set past end of file in page_mkwrite path
1937	* while mapping the last partial folio. Hence it's better to clear
1938	* all the dirty bits in the folio here.
1939	*/
1940	iomap_clear_range_dirty(folio, off: 0, len: folio_size(folio));
1941
1942	/*
1943	* Usually the writeback bit is cleared by the I/O completion handler.
1944	* But we may end up either not actually writing any blocks, or (when
1945	* there are multiple blocks in a folio) all I/O might have finished
1946	* already at this point. In that case we need to clear the writeback
1947	* bit ourselves right after unlocking the page.
1948	*/
1949	folio_unlock(folio);
1950	if (ifs) {
1951	if (atomic_dec_and_test(v: &ifs->write_bytes_pending))
1952	folio_end_writeback(folio);
1953	} else {
1954	if (!count)
1955	folio_end_writeback(folio);
1956	}
1957	mapping_set_error(mapping: inode->i_mapping, error);
1958	return error;
1959	}
1960
1961	static int iomap_do_writepage(struct folio *folio,
1962	struct writeback_control *wbc, void *data)
1963	{
1964	return iomap_writepage_map(wpc: data, wbc, folio);
1965	}
1966
1967	int
1968	iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
1969	struct iomap_writepage_ctx *wpc,
1970	const struct iomap_writeback_ops *ops)
1971	{
1972	int ret;
1973
1974	/*
1975	* Writeback from reclaim context should never happen except in the case
1976	* of a VM regression so warn about it and refuse to write the data.
1977	*/
1978	if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC | PF_KSWAPD)) ==
1979	PF_MEMALLOC))
1980	return -EIO;
1981
1982	wpc->ops = ops;
1983	ret = write_cache_pages(mapping, wbc, writepage: iomap_do_writepage, data: wpc);
1984	return iomap_submit_ioend(wpc, error: ret);
1985	}
1986	EXPORT_SYMBOL_GPL(iomap_writepages);
1987
1988	static int __init iomap_init(void)
1989	{
1990	return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
1991	offsetof(struct iomap_ioend, io_bio),
1992	flags: BIOSET_NEED_BVECS);
1993	}
1994	fs_initcall(iomap_init);
1995