linux - fs/buffer.c

3163 lines · 83.4 KiB

1	// SPDX-License-Identifier: GPL-2.0-only
2	/*
3	* linux/fs/buffer.c
4	*
5	* Copyright (C) 1991, 1992, 2002 Linus Torvalds
6	*/
7
8	/*
9	* Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
10	*
11	* Removed a lot of unnecessary code and simplified things now that
12	* the buffer cache isn't our primary cache - Andrew Tridgell 12/96
13	*
14	* Speed up hash, lru, and free list operations. Use gfp() for allocating
15	* hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
16	*
17	* Added 32k buffer block sizes - these are required older ARM systems. - RMK
18	*
19	* async buffer flushing, 1999 Andrea Arcangeli <[email protected]>
20	*/
21
22	#include <linux/kernel.h>
23	#include <linux/sched/signal.h>
24	#include <linux/syscalls.h>
25	#include <linux/fs.h>
26	#include <linux/iomap.h>
27	#include <linux/mm.h>
28	#include <linux/percpu.h>
29	#include <linux/slab.h>
30	#include <linux/capability.h>
31	#include <linux/blkdev.h>
32	#include <linux/blk-crypto.h>
33	#include <linux/file.h>
34	#include <linux/quotaops.h>
35	#include <linux/highmem.h>
36	#include <linux/export.h>
37	#include <linux/backing-dev.h>
38	#include <linux/writeback.h>
39	#include <linux/hash.h>
40	#include <linux/suspend.h>
41	#include <linux/buffer_head.h>
42	#include <linux/task_io_accounting_ops.h>
43	#include <linux/bio.h>
44	#include <linux/cpu.h>
45	#include <linux/bitops.h>
46	#include <linux/mpage.h>
47	#include <linux/bit_spinlock.h>
48	#include <linux/pagevec.h>
49	#include <linux/sched/mm.h>
50	#include <trace/events/block.h>
51	#include <linux/fscrypt.h>
52	#include <linux/fsverity.h>
53	#include <linux/sched/isolation.h>
54
55	#include "internal.h"
56
57	static int fsync_buffers_list(spinlock_t lock, struct list_head list);
58	static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
59	enum rw_hint hint, struct writeback_control *wbc);
60
61	#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
62
63	inline void touch_buffer(struct buffer_head *bh)
64	{
65	trace_block_touch_buffer(bh);
66	folio_mark_accessed(bh->b_folio);
67	}
68	EXPORT_SYMBOL(touch_buffer);
69
70	void __lock_buffer(struct buffer_head *bh)
71	{
72	wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
73	}
74	EXPORT_SYMBOL(__lock_buffer);
75
76	void unlock_buffer(struct buffer_head *bh)
77	{
78	clear_bit_unlock(BH_Lock, &bh->b_state);
79	smp_mb__after_atomic();
80	wake_up_bit(&bh->b_state, BH_Lock);
81	}
82	EXPORT_SYMBOL(unlock_buffer);
83
84	/*
85	* Returns if the folio has dirty or writeback buffers. If all the buffers
86	* are unlocked and clean then the folio_test_dirty information is stale. If
87	* any of the buffers are locked, it is assumed they are locked for IO.
88	*/
89	void buffer_check_dirty_writeback(struct folio *folio,
90	bool dirty, bool writeback)
91	{
92	struct buffer_head head, bh;
93	*dirty = false;
94	*writeback = false;
95
96	BUG_ON(!folio_test_locked(folio));
97
98	head = folio_buffers(folio);
99	if (!head)
100	return;
101
102	if (folio_test_writeback(folio))
103	*writeback = true;
104
105	bh = head;
106	do {
107	if (buffer_locked(bh))
108	*writeback = true;
109
110	if (buffer_dirty(bh))
111	*dirty = true;
112
113	bh = bh->b_this_page;
114	} while (bh != head);
115	}
116
117	/*
118	* Block until a buffer comes unlocked. This doesn't stop it
119	* from becoming locked again - you have to lock it yourself
120	* if you want to preserve its state.
121	*/
122	void __wait_on_buffer(struct buffer_head * bh)
123	{
124	wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
125	}
126	EXPORT_SYMBOL(__wait_on_buffer);
127
128	static void buffer_io_error(struct buffer_head bh, char msg)
129	{
130	if (!test_bit(BH_Quiet, &bh->b_state))
131	printk_ratelimited(KERN_ERR
132	"Buffer I/O error on dev %pg, logical block %llu%s\n",
133	bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
134	}
135
136	/*
137	* End-of-IO handler helper function which does not touch the bh after
138	* unlocking it.
139	* Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
140	* a race there is benign: unlock_buffer() only use the bh's address for
141	* hashing after unlocking the buffer, so it doesn't actually touch the bh
142	* itself.
143	*/
144	static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
145	{
146	if (uptodate) {
147	set_buffer_uptodate(bh);
148	} else {
149	/* This happens, due to failed read-ahead attempts. */
150	clear_buffer_uptodate(bh);
151	}
152	unlock_buffer(bh);
153	}
154
155	/*
156	* Default synchronous end-of-IO handler.. Just mark it up-to-date and
157	* unlock the buffer.
158	*/
159	void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
160	{
161	put_bh(bh);
162	__end_buffer_read_notouch(bh, uptodate);
163	}
164	EXPORT_SYMBOL(end_buffer_read_sync);
165
166	void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
167	{
168	if (uptodate) {
169	set_buffer_uptodate(bh);
170	} else {
171	buffer_io_error(bh, ", lost sync page write");
172	mark_buffer_write_io_error(bh);
173	clear_buffer_uptodate(bh);
174	}
175	unlock_buffer(bh);
176	put_bh(bh);
177	}
178	EXPORT_SYMBOL(end_buffer_write_sync);
179
180	static struct buffer_head *
181	__find_get_block_slow(struct block_device *bdev, sector_t block, bool atomic)
182	{
183	struct address_space *bd_mapping = bdev->bd_mapping;
184	const int blkbits = bd_mapping->host->i_blkbits;
185	struct buffer_head *ret = NULL;
186	pgoff_t index;
187	struct buffer_head *bh;
188	struct buffer_head *head;
189	struct folio *folio;
190	int all_mapped = 1;
191	static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
192
193	index = ((loff_t)block << blkbits) / PAGE_SIZE;
194	folio = __filemap_get_folio(bd_mapping, index, FGP_ACCESSED, 0);
195	if (IS_ERR(folio))
196	goto out;
197
198	/*
199	* Folio lock protects the buffers. Callers that cannot block
200	* will fallback to serializing vs try_to_free_buffers() via
201	* the i_private_lock.
202	*/
203	if (atomic)
204	spin_lock(&bd_mapping->i_private_lock);
205	else
206	folio_lock(folio);
207
208	head = folio_buffers(folio);
209	if (!head)
210	goto out_unlock;
211	/*
212	* Upon a noref migration, the folio lock serializes here;
213	* otherwise bail.
214	*/
215	if (test_bit_acquire(BH_Migrate, &head->b_state)) {
216	WARN_ON(!atomic);
217	goto out_unlock;
218	}
219
220	bh = head;
221	do {
222	if (!buffer_mapped(bh))
223	all_mapped = 0;
224	else if (bh->b_blocknr == block) {
225	ret = bh;
226	get_bh(bh);
227	goto out_unlock;
228	}
229	bh = bh->b_this_page;
230	} while (bh != head);
231
232	/* we might be here because some of the buffers on this page are
233	* not mapped. This is due to various races between
234	* file io on the block device and getblk. It gets dealt with
235	* elsewhere, don't buffer_error if we had some unmapped buffers
236	*/
237	ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
238	if (all_mapped && __ratelimit(&last_warned)) {
239	printk("__find_get_block_slow() failed. block=%llu, "
240	"b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
241	"device %pg blocksize: %d\n",
242	(unsigned long long)block,
243	(unsigned long long)bh->b_blocknr,
244	bh->b_state, bh->b_size, bdev,
245	1 << blkbits);
246	}
247	out_unlock:
248	if (atomic)
249	spin_unlock(&bd_mapping->i_private_lock);
250	else
251	folio_unlock(folio);
252	folio_put(folio);
253	out:
254	return ret;
255	}
256
257	static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
258	{
259	unsigned long flags;
260	struct buffer_head *first;
261	struct buffer_head *tmp;
262	struct folio *folio;
263	int folio_uptodate = 1;
264
265	BUG_ON(!buffer_async_read(bh));
266
267	folio = bh->b_folio;
268	if (uptodate) {
269	set_buffer_uptodate(bh);
270	} else {
271	clear_buffer_uptodate(bh);
272	buffer_io_error(bh, ", async page read");
273	}
274
275	/*
276	* Be _very_ careful from here on. Bad things can happen if
277	* two buffer heads end IO at almost the same time and both
278	* decide that the page is now completely done.
279	*/
280	first = folio_buffers(folio);
281	spin_lock_irqsave(&first->b_uptodate_lock, flags);
282	clear_buffer_async_read(bh);
283	unlock_buffer(bh);
284	tmp = bh;
285	do {
286	if (!buffer_uptodate(tmp))
287	folio_uptodate = 0;
288	if (buffer_async_read(tmp)) {
289	BUG_ON(!buffer_locked(tmp));
290	goto still_busy;
291	}
292	tmp = tmp->b_this_page;
293	} while (tmp != bh);
294	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
295
296	folio_end_read(folio, folio_uptodate);
297	return;
298
299	still_busy:
300	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
301	}
302
303	struct postprocess_bh_ctx {
304	struct work_struct work;
305	struct buffer_head *bh;
306	struct fsverity_info *vi;
307	};
308
309	static void verify_bh(struct work_struct *work)
310	{
311	struct postprocess_bh_ctx *ctx =
312	container_of(work, struct postprocess_bh_ctx, work);
313	struct buffer_head *bh = ctx->bh;
314	bool valid;
315
316	valid = fsverity_verify_blocks(ctx->vi, bh->b_folio, bh->b_size,
317	bh_offset(bh));
318	end_buffer_async_read(bh, valid);
319	kfree(ctx);
320	}
321
322	static void decrypt_bh(struct work_struct *work)
323	{
324	struct postprocess_bh_ctx *ctx =
325	container_of(work, struct postprocess_bh_ctx, work);
326	struct buffer_head *bh = ctx->bh;
327	int err;
328
329	err = fscrypt_decrypt_pagecache_blocks(bh->b_folio, bh->b_size,
330	bh_offset(bh));
331	if (err == 0 && ctx->vi) {
332	/*
333	* We use different work queues for decryption and for verity
334	* because verity may require reading metadata pages that need
335	* decryption, and we shouldn't recurse to the same workqueue.
336	*/
337	INIT_WORK(&ctx->work, verify_bh);
338	fsverity_enqueue_verify_work(&ctx->work);
339	return;
340	}
341	end_buffer_async_read(bh, err == 0);
342	kfree(ctx);
343	}
344
345	/*
346	* I/O completion handler for block_read_full_folio() - pages
347	* which come unlocked at the end of I/O.
348	*/
349	static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
350	{
351	struct inode *inode = bh->b_folio->mapping->host;
352	bool decrypt = fscrypt_inode_uses_fs_layer_crypto(inode);
353	struct fsverity_info *vi = NULL;
354
355	/* needed by ext4 */
356	if (bh->b_folio->index < DIV_ROUND_UP(inode->i_size, PAGE_SIZE))
357	vi = fsverity_get_info(inode);
358
359	/* Decrypt (with fscrypt) and/or verify (with fsverity) if needed. */
360	if (uptodate && (decrypt \|\| vi)) {
361	struct postprocess_bh_ctx ctx = kmalloc_obj(ctx, GFP_ATOMIC);
362
363	if (ctx) {
364	ctx->bh = bh;
365	ctx->vi = vi;
366	if (decrypt) {
367	INIT_WORK(&ctx->work, decrypt_bh);
368	fscrypt_enqueue_decrypt_work(&ctx->work);
369	} else {
370	INIT_WORK(&ctx->work, verify_bh);
371	fsverity_enqueue_verify_work(&ctx->work);
372	}
373	return;
374	}
375	uptodate = 0;
376	}
377	end_buffer_async_read(bh, uptodate);
378	}
379
380	/*
381	* Completion handler for block_write_full_folio() - folios which are unlocked
382	* during I/O, and which have the writeback flag cleared upon I/O completion.
383	*/
384	static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
385	{
386	unsigned long flags;
387	struct buffer_head *first;
388	struct buffer_head *tmp;
389	struct folio *folio;
390
391	BUG_ON(!buffer_async_write(bh));
392
393	folio = bh->b_folio;
394	if (uptodate) {
395	set_buffer_uptodate(bh);
396	} else {
397	buffer_io_error(bh, ", lost async page write");
398	mark_buffer_write_io_error(bh);
399	clear_buffer_uptodate(bh);
400	}
401
402	first = folio_buffers(folio);
403	spin_lock_irqsave(&first->b_uptodate_lock, flags);
404
405	clear_buffer_async_write(bh);
406	unlock_buffer(bh);
407	tmp = bh->b_this_page;
408	while (tmp != bh) {
409	if (buffer_async_write(tmp)) {
410	BUG_ON(!buffer_locked(tmp));
411	goto still_busy;
412	}
413	tmp = tmp->b_this_page;
414	}
415	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
416	folio_end_writeback(folio);
417	return;
418
419	still_busy:
420	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
421	}
422
423	/*
424	* If a page's buffers are under async readin (end_buffer_async_read
425	* completion) then there is a possibility that another thread of
426	* control could lock one of the buffers after it has completed
427	* but while some of the other buffers have not completed. This
428	* locked buffer would confuse end_buffer_async_read() into not unlocking
429	* the page. So the absence of BH_Async_Read tells end_buffer_async_read()
430	* that this buffer is not under async I/O.
431	*
432	* The page comes unlocked when it has no locked buffer_async buffers
433	* left.
434	*
435	* PageLocked prevents anyone starting new async I/O reads any of
436	* the buffers.
437	*
438	* PageWriteback is used to prevent simultaneous writeout of the same
439	* page.
440	*
441	* PageLocked prevents anyone from starting writeback of a page which is
442	* under read I/O (PageWriteback is only ever set against a locked page).
443	*/
444	static void mark_buffer_async_read(struct buffer_head *bh)
445	{
446	bh->b_end_io = end_buffer_async_read_io;
447	set_buffer_async_read(bh);
448	}
449
450	static void mark_buffer_async_write_endio(struct buffer_head *bh,
451	bh_end_io_t *handler)
452	{
453	bh->b_end_io = handler;
454	set_buffer_async_write(bh);
455	}
456
457	void mark_buffer_async_write(struct buffer_head *bh)
458	{
459	mark_buffer_async_write_endio(bh, end_buffer_async_write);
460	}
461	EXPORT_SYMBOL(mark_buffer_async_write);
462
463
464	/*
465	* fs/buffer.c contains helper functions for buffer-backed address space's
466	* fsync functions. A common requirement for buffer-based filesystems is
467	* that certain data from the backing blockdev needs to be written out for
468	* a successful fsync(). For example, ext2 indirect blocks need to be
469	* written back and waited upon before fsync() returns.
470	*
471	* The functions mark_buffer_dirty_inode(), fsync_inode_buffers(),
472	* inode_has_buffers() and invalidate_inode_buffers() are provided for the
473	* management of a list of dependent buffers at ->i_mapping->i_private_list.
474	*
475	* Locking is a little subtle: try_to_free_buffers() will remove buffers
476	* from their controlling inode's queue when they are being freed. But
477	* try_to_free_buffers() will be operating against the blockdev mapping
478	* at the time, not against the S_ISREG file which depends on those buffers.
479	* So the locking for i_private_list is via the i_private_lock in the address_space
480	* which backs the buffers. Which is different from the address_space
481	* against which the buffers are listed. So for a particular address_space,
482	* mapping->i_private_lock does not protect mapping->i_private_list! In fact,
483	* mapping->i_private_list will always be protected by the backing blockdev's
484	* ->i_private_lock.
485	*
486	* Which introduces a requirement: all buffers on an address_space's
487	* ->i_private_list must be from the same address_space: the blockdev's.
488	*
489	* address_spaces which do not place buffers at ->i_private_list via these
490	* utility functions are free to use i_private_lock and i_private_list for
491	* whatever they want. The only requirement is that list_empty(i_private_list)
492	* be true at clear_inode() time.
493	*
494	* FIXME: clear_inode should not call invalidate_inode_buffers(). The
495	* filesystems should do that. invalidate_inode_buffers() should just go
496	* BUG_ON(!list_empty).
497	*
498	* FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
499	* take an address_space, not an inode. And it should be called
500	* mark_buffer_dirty_fsync() to clearly define why those buffers are being
501	* queued up.
502	*
503	* FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
504	* list if it is already on a list. Because if the buffer is on a list,
505	* it must already be on the right one. If not, the filesystem is being
506	* silly. This will save a ton of locking. But first we have to ensure
507	* that buffers are taken off the old inode's list when they are freed
508	* (presumably in truncate). That requires careful auditing of all
509	* filesystems (do it inside bforget()). It could also be done by bringing
510	* b_inode back.
511	*/
512
513	/*
514	* The buffer's backing address_space's i_private_lock must be held
515	*/
516	static void __remove_assoc_queue(struct buffer_head *bh)
517	{
518	list_del_init(&bh->b_assoc_buffers);
519	WARN_ON(!bh->b_assoc_map);
520	bh->b_assoc_map = NULL;
521	}
522
523	int inode_has_buffers(struct inode *inode)
524	{
525	return !list_empty(&inode->i_data.i_private_list);
526	}
527
528	/*
529	* osync is designed to support O_SYNC io. It waits synchronously for
530	* all already-submitted IO to complete, but does not queue any new
531	* writes to the disk.
532	*
533	* To do O_SYNC writes, just queue the buffer writes with write_dirty_buffer
534	* as you dirty the buffers, and then use osync_inode_buffers to wait for
535	* completion. Any other dirty buffers which are not yet queued for
536	* write will not be flushed to disk by the osync.
537	*/
538	static int osync_buffers_list(spinlock_t lock, struct list_head list)
539	{
540	struct buffer_head *bh;
541	struct list_head *p;
542	int err = 0;
543
544	spin_lock(lock);
545	repeat:
546	list_for_each_prev(p, list) {
547	bh = BH_ENTRY(p);
548	if (buffer_locked(bh)) {
549	get_bh(bh);
550	spin_unlock(lock);
551	wait_on_buffer(bh);
552	if (!buffer_uptodate(bh))
553	err = -EIO;
554	brelse(bh);
555	spin_lock(lock);
556	goto repeat;
557	}
558	}
559	spin_unlock(lock);
560	return err;
561	}
562
563	/**
564	* sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
565	* @mapping: the mapping which wants those buffers written
566	*
567	* Starts I/O against the buffers at mapping->i_private_list, and waits upon
568	* that I/O.
569	*
570	* Basically, this is a convenience function for fsync().
571	* @mapping is a file or directory which needs those buffers to be written for
572	* a successful fsync().
573	*/
574	int sync_mapping_buffers(struct address_space *mapping)
575	{
576	struct address_space *buffer_mapping = mapping->i_private_data;
577
578	if (buffer_mapping == NULL \|\| list_empty(&mapping->i_private_list))
579	return 0;
580
581	return fsync_buffers_list(&buffer_mapping->i_private_lock,
582	&mapping->i_private_list);
583	}
584	EXPORT_SYMBOL(sync_mapping_buffers);
585
586	/**
587	* generic_buffers_fsync_noflush - generic buffer fsync implementation
588	* for simple filesystems with no inode lock
589	*
590	* @file: file to synchronize
591	* @start: start offset in bytes
592	* @end: end offset in bytes (inclusive)
593	* @datasync: only synchronize essential metadata if true
594	*
595	* This is a generic implementation of the fsync method for simple
596	* filesystems which track all non-inode metadata in the buffers list
597	* hanging off the address_space structure.
598	*/
599	int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end,
600	bool datasync)
601	{
602	struct inode *inode = file->f_mapping->host;
603	int err;
604	int ret;
605
606	err = file_write_and_wait_range(file, start, end);
607	if (err)
608	return err;
609
610	ret = sync_mapping_buffers(inode->i_mapping);
611	if (!(inode_state_read_once(inode) & I_DIRTY_ALL))
612	goto out;
613	if (datasync && !(inode_state_read_once(inode) & I_DIRTY_DATASYNC))
614	goto out;
615
616	err = sync_inode_metadata(inode, 1);
617	if (ret == 0)
618	ret = err;
619
620	out:
621	/* check and advance again to catch errors after syncing out buffers */
622	err = file_check_and_advance_wb_err(file);
623	if (ret == 0)
624	ret = err;
625	return ret;
626	}
627	EXPORT_SYMBOL(generic_buffers_fsync_noflush);
628
629	/**
630	* generic_buffers_fsync - generic buffer fsync implementation
631	* for simple filesystems with no inode lock
632	*
633	* @file: file to synchronize
634	* @start: start offset in bytes
635	* @end: end offset in bytes (inclusive)
636	* @datasync: only synchronize essential metadata if true
637	*
638	* This is a generic implementation of the fsync method for simple
639	* filesystems which track all non-inode metadata in the buffers list
640	* hanging off the address_space structure. This also makes sure that
641	* a device cache flush operation is called at the end.
642	*/
643	int generic_buffers_fsync(struct file *file, loff_t start, loff_t end,
644	bool datasync)
645	{
646	struct inode *inode = file->f_mapping->host;
647	int ret;
648
649	ret = generic_buffers_fsync_noflush(file, start, end, datasync);
650	if (!ret)
651	ret = blkdev_issue_flush(inode->i_sb->s_bdev);
652	return ret;
653	}
654	EXPORT_SYMBOL(generic_buffers_fsync);
655
656	/*
657	* Called when we've recently written block `bblock', and it is known that
658	* `bblock' was for a buffer_boundary() buffer. This means that the block at
659	* `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
660	* dirty, schedule it for IO. So that indirects merge nicely with their data.
661	*/
662	void write_boundary_block(struct block_device *bdev,
663	sector_t bblock, unsigned blocksize)
664	{
665	struct buffer_head *bh;
666
667	bh = __find_get_block_nonatomic(bdev, bblock + 1, blocksize);
668	if (bh) {
669	if (buffer_dirty(bh))
670	write_dirty_buffer(bh, 0);
671	put_bh(bh);
672	}
673	}
674
675	void mark_buffer_dirty_inode(struct buffer_head bh, struct inode inode)
676	{
677	struct address_space *mapping = inode->i_mapping;
678	struct address_space *buffer_mapping = bh->b_folio->mapping;
679
680	mark_buffer_dirty(bh);
681	if (!mapping->i_private_data) {
682	mapping->i_private_data = buffer_mapping;
683	} else {
684	BUG_ON(mapping->i_private_data != buffer_mapping);
685	}
686	if (!bh->b_assoc_map) {
687	spin_lock(&buffer_mapping->i_private_lock);
688	list_move_tail(&bh->b_assoc_buffers,
689	&mapping->i_private_list);
690	bh->b_assoc_map = mapping;
691	spin_unlock(&buffer_mapping->i_private_lock);
692	}
693	}
694	EXPORT_SYMBOL(mark_buffer_dirty_inode);
695
696	/**
697	* block_dirty_folio - Mark a folio as dirty.
698	* @mapping: The address space containing this folio.
699	* @folio: The folio to mark dirty.
700	*
701	* Filesystems which use buffer_heads can use this function as their
702	* ->dirty_folio implementation. Some filesystems need to do a little
703	* work before calling this function. Filesystems which do not use
704	* buffer_heads should call filemap_dirty_folio() instead.
705	*
706	* If the folio has buffers, the uptodate buffers are set dirty, to
707	* preserve dirty-state coherency between the folio and the buffers.
708	* Buffers added to a dirty folio are created dirty.
709	*
710	* The buffers are dirtied before the folio is dirtied. There's a small
711	* race window in which writeback may see the folio cleanness but not the
712	* buffer dirtiness. That's fine. If this code were to set the folio
713	* dirty before the buffers, writeback could clear the folio dirty flag,
714	* see a bunch of clean buffers and we'd end up with dirty buffers/clean
715	* folio on the dirty folio list.
716	*
717	* We use i_private_lock to lock against try_to_free_buffers() while
718	* using the folio's buffer list. This also prevents clean buffers
719	* being added to the folio after it was set dirty.
720	*
721	* Context: May only be called from process context. Does not sleep.
722	* Caller must ensure that @folio cannot be truncated during this call,
723	* typically by holding the folio lock or having a page in the folio
724	* mapped and holding the page table lock.
725	*
726	* Return: True if the folio was dirtied; false if it was already dirtied.
727	*/
728	bool block_dirty_folio(struct address_space mapping, struct folio folio)
729	{
730	struct buffer_head *head;
731	bool newly_dirty;
732
733	spin_lock(&mapping->i_private_lock);
734	head = folio_buffers(folio);
735	if (head) {
736	struct buffer_head *bh = head;
737
738	do {
739	set_buffer_dirty(bh);
740	bh = bh->b_this_page;
741	} while (bh != head);
742	}
743	/*
744	* Lock out page's memcg migration to keep PageDirty
745	* synchronized with per-memcg dirty page counters.
746	*/
747	newly_dirty = !folio_test_set_dirty(folio);
748	spin_unlock(&mapping->i_private_lock);
749
750	if (newly_dirty)
751	__folio_mark_dirty(folio, mapping, 1);
752
753	if (newly_dirty)
754	__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
755
756	return newly_dirty;
757	}
758	EXPORT_SYMBOL(block_dirty_folio);
759
760	/*
761	* Write out and wait upon a list of buffers.
762	*
763	* We have conflicting pressures: we want to make sure that all
764	* initially dirty buffers get waited on, but that any subsequently
765	* dirtied buffers don't. After all, we don't want fsync to last
766	* forever if somebody is actively writing to the file.
767	*
768	* Do this in two main stages: first we copy dirty buffers to a
769	* temporary inode list, queueing the writes as we go. Then we clean
770	* up, waiting for those writes to complete.
771	*
772	* During this second stage, any subsequent updates to the file may end
773	* up refiling the buffer on the original inode's dirty list again, so
774	* there is a chance we will end up with a buffer queued for write but
775	* not yet completed on that list. So, as a final cleanup we go through
776	* the osync code to catch these locked, dirty buffers without requeuing
777	* any newly dirty buffers for write.
778	*/
779	static int fsync_buffers_list(spinlock_t lock, struct list_head list)
780	{
781	struct buffer_head *bh;
782	struct address_space *mapping;
783	int err = 0, err2;
784	struct blk_plug plug;
785	LIST_HEAD(tmp);
786
787	blk_start_plug(&plug);
788
789	spin_lock(lock);
790	while (!list_empty(list)) {
791	bh = BH_ENTRY(list->next);
792	mapping = bh->b_assoc_map;
793	__remove_assoc_queue(bh);
794	/* Avoid race with mark_buffer_dirty_inode() which does
795	* a lockless check and we rely on seeing the dirty bit */
796	smp_mb();
797	if (buffer_dirty(bh) \|\| buffer_locked(bh)) {
798	list_add(&bh->b_assoc_buffers, &tmp);
799	bh->b_assoc_map = mapping;
800	if (buffer_dirty(bh)) {
801	get_bh(bh);
802	spin_unlock(lock);
803	/*
804	* Ensure any pending I/O completes so that
805	* write_dirty_buffer() actually writes the
806	* current contents - it is a noop if I/O is
807	* still in flight on potentially older
808	* contents.
809	*/
810	write_dirty_buffer(bh, REQ_SYNC);
811
812	/*
813	* Kick off IO for the previous mapping. Note
814	* that we will not run the very last mapping,
815	* wait_on_buffer() will do that for us
816	* through sync_buffer().
817	*/
818	brelse(bh);
819	spin_lock(lock);
820	}
821	}
822	}
823
824	spin_unlock(lock);
825	blk_finish_plug(&plug);
826	spin_lock(lock);
827
828	while (!list_empty(&tmp)) {
829	bh = BH_ENTRY(tmp.prev);
830	get_bh(bh);
831	mapping = bh->b_assoc_map;
832	__remove_assoc_queue(bh);
833	/* Avoid race with mark_buffer_dirty_inode() which does
834	* a lockless check and we rely on seeing the dirty bit */
835	smp_mb();
836	if (buffer_dirty(bh)) {
837	list_add(&bh->b_assoc_buffers,
838	&mapping->i_private_list);
839	bh->b_assoc_map = mapping;
840	}
841	spin_unlock(lock);
842	wait_on_buffer(bh);
843	if (!buffer_uptodate(bh))
844	err = -EIO;
845	brelse(bh);
846	spin_lock(lock);
847	}
848
849	spin_unlock(lock);
850	err2 = osync_buffers_list(lock, list);
851	if (err)
852	return err;
853	else
854	return err2;
855	}
856
857	/*
858	* Invalidate any and all dirty buffers on a given inode. We are
859	* probably unmounting the fs, but that doesn't mean we have already
860	* done a sync(). Just drop the buffers from the inode list.
861	*
862	* NOTE: we take the inode's blockdev's mapping's i_private_lock. Which
863	* assumes that all the buffers are against the blockdev.
864	*/
865	void invalidate_inode_buffers(struct inode *inode)
866	{
867	if (inode_has_buffers(inode)) {
868	struct address_space *mapping = &inode->i_data;
869	struct list_head *list = &mapping->i_private_list;
870	struct address_space *buffer_mapping = mapping->i_private_data;
871
872	spin_lock(&buffer_mapping->i_private_lock);
873	while (!list_empty(list))
874	__remove_assoc_queue(BH_ENTRY(list->next));
875	spin_unlock(&buffer_mapping->i_private_lock);
876	}
877	}
878	EXPORT_SYMBOL(invalidate_inode_buffers);
879
880	/*
881	* Remove any clean buffers from the inode's buffer list. This is called
882	* when we're trying to free the inode itself. Those buffers can pin it.
883	*
884	* Returns true if all buffers were removed.
885	*/
886	int remove_inode_buffers(struct inode *inode)
887	{
888	int ret = 1;
889
890	if (inode_has_buffers(inode)) {
891	struct address_space *mapping = &inode->i_data;
892	struct list_head *list = &mapping->i_private_list;
893	struct address_space *buffer_mapping = mapping->i_private_data;
894
895	spin_lock(&buffer_mapping->i_private_lock);
896	while (!list_empty(list)) {
897	struct buffer_head *bh = BH_ENTRY(list->next);
898	if (buffer_dirty(bh)) {
899	ret = 0;
900	break;
901	}
902	__remove_assoc_queue(bh);
903	}
904	spin_unlock(&buffer_mapping->i_private_lock);
905	}
906	return ret;
907	}
908
909	/*
910	* Create the appropriate buffers when given a folio for data area and
911	* the size of each buffer.. Use the bh->b_this_page linked list to
912	* follow the buffers created. Return NULL if unable to create more
913	* buffers.
914	*
915	* The retry flag is used to differentiate async IO (paging, swapping)
916	* which may not fail from ordinary buffer allocations.
917	*/
918	struct buffer_head folio_alloc_buffers(struct folio folio, unsigned long size,
919	gfp_t gfp)
920	{
921	struct buffer_head bh, head;
922	long offset;
923	struct mem_cgroup memcg, old_memcg;
924
925	/* The folio lock pins the memcg */
926	memcg = folio_memcg(folio);
927	old_memcg = set_active_memcg(memcg);
928
929	head = NULL;
930	offset = folio_size(folio);
931	while ((offset -= size) >= 0) {
932	bh = alloc_buffer_head(gfp);
933	if (!bh)
934	goto no_grow;
935
936	bh->b_this_page = head;
937	bh->b_blocknr = -1;
938	head = bh;
939
940	bh->b_size = size;
941
942	/* Link the buffer to its folio */
943	folio_set_bh(bh, folio, offset);
944	}
945	out:
946	set_active_memcg(old_memcg);
947	return head;
948	/*
949	* In case anything failed, we just free everything we got.
950	*/
951	no_grow:
952	if (head) {
953	do {
954	bh = head;
955	head = head->b_this_page;
956	free_buffer_head(bh);
957	} while (head);
958	}
959
960	goto out;
961	}
962	EXPORT_SYMBOL_GPL(folio_alloc_buffers);
963
964	struct buffer_head alloc_page_buffers(struct page page, unsigned long size)
965	{
966	gfp_t gfp = GFP_NOFS \| __GFP_ACCOUNT;
967
968	return folio_alloc_buffers(page_folio(page), size, gfp);
969	}
970	EXPORT_SYMBOL_GPL(alloc_page_buffers);
971
972	static inline void link_dev_buffers(struct folio *folio,
973	struct buffer_head *head)
974	{
975	struct buffer_head bh, tail;
976
977	bh = head;
978	do {
979	tail = bh;
980	bh = bh->b_this_page;
981	} while (bh);
982	tail->b_this_page = head;
983	folio_attach_private(folio, head);
984	}
985
986	static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
987	{
988	sector_t retval = ~((sector_t)0);
989	loff_t sz = bdev_nr_bytes(bdev);
990
991	if (sz) {
992	unsigned int sizebits = blksize_bits(size);
993	retval = (sz >> sizebits);
994	}
995	return retval;
996	}
997
998	/*
999	* Initialise the state of a blockdev folio's buffers.
1000	*/
1001	static sector_t folio_init_buffers(struct folio *folio,
1002	struct block_device *bdev, unsigned size)
1003	{
1004	struct buffer_head *head = folio_buffers(folio);
1005	struct buffer_head *bh = head;
1006	bool uptodate = folio_test_uptodate(folio);
1007	sector_t block = div_u64(folio_pos(folio), size);
1008	sector_t end_block = blkdev_max_block(bdev, size);
1009
1010	do {
1011	if (!buffer_mapped(bh)) {
1012	bh->b_end_io = NULL;
1013	bh->b_private = NULL;
1014	bh->b_bdev = bdev;
1015	bh->b_blocknr = block;
1016	if (uptodate)
1017	set_buffer_uptodate(bh);
1018	if (block < end_block)
1019	set_buffer_mapped(bh);
1020	}
1021	block++;
1022	bh = bh->b_this_page;
1023	} while (bh != head);
1024
1025	/*
1026	* Caller needs to validate requested block against end of device.
1027	*/
1028	return end_block;
1029	}
1030
1031	/*
1032	* Create the page-cache folio that contains the requested block.
1033	*
1034	* This is used purely for blockdev mappings.
1035	*
1036	* Returns false if we have a failure which cannot be cured by retrying
1037	* without sleeping. Returns true if we succeeded, or the caller should retry.
1038	*/
1039	static bool grow_dev_folio(struct block_device *bdev, sector_t block,
1040	pgoff_t index, unsigned size, gfp_t gfp)
1041	{
1042	struct address_space *mapping = bdev->bd_mapping;
1043	struct folio *folio;
1044	struct buffer_head *bh;
1045	sector_t end_block = 0;
1046
1047	folio = __filemap_get_folio(mapping, index,
1048	FGP_LOCK \| FGP_ACCESSED \| FGP_CREAT, gfp);
1049	if (IS_ERR(folio))
1050	return false;
1051
1052	bh = folio_buffers(folio);
1053	if (bh) {
1054	if (bh->b_size == size) {
1055	end_block = folio_init_buffers(folio, bdev, size);
1056	goto unlock;
1057	}
1058
1059	/*
1060	* Retrying may succeed; for example the folio may finish
1061	* writeback, or buffers may be cleaned. This should not
1062	* happen very often; maybe we have old buffers attached to
1063	* this blockdev's page cache and we're trying to change
1064	* the block size?
1065	*/
1066	if (!try_to_free_buffers(folio)) {
1067	end_block = ~0ULL;
1068	goto unlock;
1069	}
1070	}
1071
1072	bh = folio_alloc_buffers(folio, size, gfp \| __GFP_ACCOUNT);
1073	if (!bh)
1074	goto unlock;
1075
1076	/*
1077	* Link the folio to the buffers and initialise them. Take the
1078	* lock to be atomic wrt __find_get_block(), which does not
1079	* run under the folio lock.
1080	*/
1081	spin_lock(&mapping->i_private_lock);
1082	link_dev_buffers(folio, bh);
1083	end_block = folio_init_buffers(folio, bdev, size);
1084	spin_unlock(&mapping->i_private_lock);
1085	unlock:
1086	folio_unlock(folio);
1087	folio_put(folio);
1088	return block < end_block;
1089	}
1090
1091	/*
1092	* Create buffers for the specified block device block's folio. If
1093	* that folio was dirty, the buffers are set dirty also. Returns false
1094	* if we've hit a permanent error.
1095	*/
1096	static bool grow_buffers(struct block_device *bdev, sector_t block,
1097	unsigned size, gfp_t gfp)
1098	{
1099	loff_t pos;
1100
1101	/*
1102	* Check for a block which lies outside our maximum possible
1103	* pagecache index.
1104	*/
1105	if (check_mul_overflow(block, (sector_t)size, &pos) \|\| pos > MAX_LFS_FILESIZE) {
1106	printk(KERN_ERR "%s: requested out-of-range block %llu for device %pg\n",
1107	__func__, (unsigned long long)block,
1108	bdev);
1109	return false;
1110	}
1111
1112	/* Create a folio with the proper size buffers */
1113	return grow_dev_folio(bdev, block, pos / PAGE_SIZE, size, gfp);
1114	}
1115
1116	static struct buffer_head *
1117	__getblk_slow(struct block_device *bdev, sector_t block,
1118	unsigned size, gfp_t gfp)
1119	{
1120	bool blocking = gfpflags_allow_blocking(gfp);
1121
1122	if (WARN_ON_ONCE(!IS_ALIGNED(size, bdev_logical_block_size(bdev)))) {
1123	printk(KERN_ERR "getblk(): block size %d not aligned to logical block size %d\n",
1124	size, bdev_logical_block_size(bdev));
1125	return NULL;
1126	}
1127
1128	for (;;) {
1129	struct buffer_head *bh;
1130
1131	if (!grow_buffers(bdev, block, size, gfp))
1132	return NULL;
1133
1134	if (blocking)
1135	bh = __find_get_block_nonatomic(bdev, block, size);
1136	else
1137	bh = __find_get_block(bdev, block, size);
1138	if (bh)
1139	return bh;
1140	}
1141	}
1142
1143	/*
1144	* The relationship between dirty buffers and dirty pages:
1145	*
1146	* Whenever a page has any dirty buffers, the page's dirty bit is set, and
1147	* the page is tagged dirty in the page cache.
1148	*
1149	* At all times, the dirtiness of the buffers represents the dirtiness of
1150	* subsections of the page. If the page has buffers, the page dirty bit is
1151	* merely a hint about the true dirty state.
1152	*
1153	* When a page is set dirty in its entirety, all its buffers are marked dirty
1154	* (if the page has buffers).
1155	*
1156	* When a buffer is marked dirty, its page is dirtied, but the page's other
1157	* buffers are not.
1158	*
1159	* Also. When blockdev buffers are explicitly read with bread(), they
1160	* individually become uptodate. But their backing page remains not
1161	* uptodate - even if all of its buffers are uptodate. A subsequent
1162	* block_read_full_folio() against that folio will discover all the uptodate
1163	* buffers, will set the folio uptodate and will perform no I/O.
1164	*/
1165
1166	/**
1167	* mark_buffer_dirty - mark a buffer_head as needing writeout
1168	* @bh: the buffer_head to mark dirty
1169	*
1170	* mark_buffer_dirty() will set the dirty bit against the buffer, then set
1171	* its backing page dirty, then tag the page as dirty in the page cache
1172	* and then attach the address_space's inode to its superblock's dirty
1173	* inode list.
1174	*
1175	* mark_buffer_dirty() is atomic. It takes bh->b_folio->mapping->i_private_lock,
1176	* i_pages lock and mapping->host->i_lock.
1177	*/
1178	void mark_buffer_dirty(struct buffer_head *bh)
1179	{
1180	WARN_ON_ONCE(!buffer_uptodate(bh));
1181
1182	trace_block_dirty_buffer(bh);
1183
1184	/*
1185	* Very carefully optimize the it-is-already-dirty case.
1186	*
1187	* Don't let the final "is it dirty" escape to before we
1188	* perhaps modified the buffer.
1189	*/
1190	if (buffer_dirty(bh)) {
1191	smp_mb();
1192	if (buffer_dirty(bh))
1193	return;
1194	}
1195
1196	if (!test_set_buffer_dirty(bh)) {
1197	struct folio *folio = bh->b_folio;
1198	struct address_space *mapping = NULL;
1199
1200	if (!folio_test_set_dirty(folio)) {
1201	mapping = folio->mapping;
1202	if (mapping)
1203	__folio_mark_dirty(folio, mapping, 0);
1204	}
1205	if (mapping)
1206	__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1207	}
1208	}
1209	EXPORT_SYMBOL(mark_buffer_dirty);
1210
1211	void mark_buffer_write_io_error(struct buffer_head *bh)
1212	{
1213	set_buffer_write_io_error(bh);
1214	/* FIXME: do we need to set this in both places? */
1215	if (bh->b_folio && bh->b_folio->mapping)
1216	mapping_set_error(bh->b_folio->mapping, -EIO);
1217	if (bh->b_assoc_map)
1218	mapping_set_error(bh->b_assoc_map, -EIO);
1219	}
1220	EXPORT_SYMBOL(mark_buffer_write_io_error);
1221
1222	/**
1223	* __brelse - Release a buffer.
1224	* @bh: The buffer to release.
1225	*
1226	* This variant of brelse() can be called if @bh is guaranteed to not be NULL.
1227	*/
1228	void __brelse(struct buffer_head *bh)
1229	{
1230	if (atomic_read(&bh->b_count)) {
1231	put_bh(bh);
1232	return;
1233	}
1234	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1235	}
1236	EXPORT_SYMBOL(__brelse);
1237
1238	/**
1239	* __bforget - Discard any dirty data in a buffer.
1240	* @bh: The buffer to forget.
1241	*
1242	* This variant of bforget() can be called if @bh is guaranteed to not
1243	* be NULL.
1244	*/
1245	void __bforget(struct buffer_head *bh)
1246	{
1247	clear_buffer_dirty(bh);
1248	if (bh->b_assoc_map) {
1249	struct address_space *buffer_mapping = bh->b_folio->mapping;
1250
1251	spin_lock(&buffer_mapping->i_private_lock);
1252	list_del_init(&bh->b_assoc_buffers);
1253	bh->b_assoc_map = NULL;
1254	spin_unlock(&buffer_mapping->i_private_lock);
1255	}
1256	__brelse(bh);
1257	}
1258	EXPORT_SYMBOL(__bforget);
1259
1260	static struct buffer_head __bread_slow(struct buffer_head bh)
1261	{
1262	lock_buffer(bh);
1263	if (buffer_uptodate(bh)) {
1264	unlock_buffer(bh);
1265	return bh;
1266	} else {
1267	get_bh(bh);
1268	bh->b_end_io = end_buffer_read_sync;
1269	submit_bh(REQ_OP_READ, bh);
1270	wait_on_buffer(bh);
1271	if (buffer_uptodate(bh))
1272	return bh;
1273	}
1274	brelse(bh);
1275	return NULL;
1276	}
1277
1278	/*
1279	* Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1280	* The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1281	* refcount elevated by one when they're in an LRU. A buffer can only appear
1282	* once in a particular CPU's LRU. A single buffer can be present in multiple
1283	* CPU's LRUs at the same time.
1284	*
1285	* This is a transparent caching front-end to sb_bread(), sb_getblk() and
1286	* sb_find_get_block().
1287	*
1288	* The LRUs themselves only need locking against invalidate_bh_lrus. We use
1289	* a local interrupt disable for that.
1290	*/
1291
1292	#define BH_LRU_SIZE 16
1293
1294	struct bh_lru {
1295	struct buffer_head *bhs[BH_LRU_SIZE];
1296	};
1297
1298	static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1299
1300	#ifdef CONFIG_SMP
1301	#define bh_lru_lock() local_irq_disable()
1302	#define bh_lru_unlock() local_irq_enable()
1303	#else
1304	#define bh_lru_lock() preempt_disable()
1305	#define bh_lru_unlock() preempt_enable()
1306	#endif
1307
1308	static inline void check_irqs_on(void)
1309	{
1310	#ifdef irqs_disabled
1311	BUG_ON(irqs_disabled());
1312	#endif
1313	}
1314
1315	/*
1316	* Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1317	* inserted at the front, and the buffer_head at the back if any is evicted.
1318	* Or, if already in the LRU it is moved to the front.
1319	*/
1320	static void bh_lru_install(struct buffer_head *bh)
1321	{
1322	struct buffer_head *evictee = bh;
1323	struct bh_lru *b;
1324	int i;
1325
1326	check_irqs_on();
1327	bh_lru_lock();
1328
1329	/*
1330	* the refcount of buffer_head in bh_lru prevents dropping the
1331	* attached page(i.e., try_to_free_buffers) so it could cause
1332	* failing page migration.
1333	* Skip putting upcoming bh into bh_lru until migration is done.
1334	*/
1335	if (lru_cache_disabled() \|\| cpu_is_isolated(smp_processor_id())) {
1336	bh_lru_unlock();
1337	return;
1338	}
1339
1340	b = this_cpu_ptr(&bh_lrus);
1341	for (i = 0; i < BH_LRU_SIZE; i++) {
1342	swap(evictee, b->bhs[i]);
1343	if (evictee == bh) {
1344	bh_lru_unlock();
1345	return;
1346	}
1347	}
1348
1349	get_bh(bh);
1350	bh_lru_unlock();
1351	brelse(evictee);
1352	}
1353
1354	/*
1355	* Look up the bh in this cpu's LRU. If it's there, move it to the head.
1356	*/
1357	static struct buffer_head *
1358	lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1359	{
1360	struct buffer_head *ret = NULL;
1361	unsigned int i;
1362
1363	check_irqs_on();
1364	bh_lru_lock();
1365	if (cpu_is_isolated(smp_processor_id())) {
1366	bh_lru_unlock();
1367	return NULL;
1368	}
1369	for (i = 0; i < BH_LRU_SIZE; i++) {
1370	struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1371
1372	if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1373	bh->b_size == size) {
1374	if (i) {
1375	while (i) {
1376	__this_cpu_write(bh_lrus.bhs[i],
1377	__this_cpu_read(bh_lrus.bhs[i - 1]));
1378	i--;
1379	}
1380	__this_cpu_write(bh_lrus.bhs[0], bh);
1381	}
1382	get_bh(bh);
1383	ret = bh;
1384	break;
1385	}
1386	}
1387	bh_lru_unlock();
1388	return ret;
1389	}
1390
1391	/*
1392	* Perform a pagecache lookup for the matching buffer. If it's there, refresh
1393	* it in the LRU and mark it as accessed. If it is not present then return
1394	* NULL. Atomic context callers may also return NULL if the buffer is being
1395	* migrated; similarly the page is not marked accessed either.
1396	*/
1397	static struct buffer_head *
1398	find_get_block_common(struct block_device *bdev, sector_t block,
1399	unsigned size, bool atomic)
1400	{
1401	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1402
1403	if (bh == NULL) {
1404	/* __find_get_block_slow will mark the page accessed */
1405	bh = __find_get_block_slow(bdev, block, atomic);
1406	if (bh)
1407	bh_lru_install(bh);
1408	} else
1409	touch_buffer(bh);
1410
1411	return bh;
1412	}
1413
1414	struct buffer_head *
1415	__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1416	{
1417	return find_get_block_common(bdev, block, size, true);
1418	}
1419	EXPORT_SYMBOL(__find_get_block);
1420
1421	/* same as __find_get_block() but allows sleeping contexts */
1422	struct buffer_head *
1423	__find_get_block_nonatomic(struct block_device *bdev, sector_t block,
1424	unsigned size)
1425	{
1426	return find_get_block_common(bdev, block, size, false);
1427	}
1428	EXPORT_SYMBOL(__find_get_block_nonatomic);
1429
1430	/**
1431	* bdev_getblk - Get a buffer_head in a block device's buffer cache.
1432	* @bdev: The block device.
1433	* @block: The block number.
1434	* @size: The size of buffer_heads for this @bdev.
1435	* @gfp: The memory allocation flags to use.
1436	*
1437	* The returned buffer head has its reference count incremented, but is
1438	* not locked. The caller should call brelse() when it has finished
1439	* with the buffer. The buffer may not be uptodate. If needed, the
1440	* caller can bring it uptodate either by reading it or overwriting it.
1441	*
1442	* Return: The buffer head, or NULL if memory could not be allocated.
1443	*/
1444	struct buffer_head bdev_getblk(struct block_device bdev, sector_t block,
1445	unsigned size, gfp_t gfp)
1446	{
1447	struct buffer_head *bh;
1448
1449	if (gfpflags_allow_blocking(gfp))
1450	bh = __find_get_block_nonatomic(bdev, block, size);
1451	else
1452	bh = __find_get_block(bdev, block, size);
1453
1454	might_alloc(gfp);
1455	if (bh)
1456	return bh;
1457
1458	return __getblk_slow(bdev, block, size, gfp);
1459	}
1460	EXPORT_SYMBOL(bdev_getblk);
1461
1462	/*
1463	* Do async read-ahead on a buffer..
1464	*/
1465	void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1466	{
1467	struct buffer_head *bh = bdev_getblk(bdev, block, size,
1468	GFP_NOWAIT \| __GFP_MOVABLE);
1469
1470	if (likely(bh)) {
1471	bh_readahead(bh, REQ_RAHEAD);
1472	brelse(bh);
1473	}
1474	}
1475	EXPORT_SYMBOL(__breadahead);
1476
1477	/**
1478	* __bread_gfp() - Read a block.
1479	* @bdev: The block device to read from.
1480	* @block: Block number in units of block size.
1481	* @size: The block size of this device in bytes.
1482	* @gfp: Not page allocation flags; see below.
1483	*
1484	* You are not expected to call this function. You should use one of
1485	* sb_bread(), sb_bread_unmovable() or __bread().
1486	*
1487	* Read a specified block, and return the buffer head that refers to it.
1488	* If @gfp is 0, the memory will be allocated using the block device's
1489	* default GFP flags. If @gfp is __GFP_MOVABLE, the memory may be
1490	* allocated from a movable area. Do not pass in a complete set of
1491	* GFP flags.
1492	*
1493	* The returned buffer head has its refcount increased. The caller should
1494	* call brelse() when it has finished with the buffer.
1495	*
1496	* Context: May sleep waiting for I/O.
1497	* Return: NULL if the block was unreadable.
1498	*/
1499	struct buffer_head __bread_gfp(struct block_device bdev, sector_t block,
1500	unsigned size, gfp_t gfp)
1501	{
1502	struct buffer_head *bh;
1503
1504	gfp \|= mapping_gfp_constraint(bdev->bd_mapping, ~__GFP_FS);
1505
1506	/*
1507	* Prefer looping in the allocator rather than here, at least that
1508	* code knows what it's doing.
1509	*/
1510	gfp \|= __GFP_NOFAIL;
1511
1512	bh = bdev_getblk(bdev, block, size, gfp);
1513
1514	if (likely(bh) && !buffer_uptodate(bh))
1515	bh = __bread_slow(bh);
1516	return bh;
1517	}
1518	EXPORT_SYMBOL(__bread_gfp);
1519
1520	static void __invalidate_bh_lrus(struct bh_lru *b)
1521	{
1522	int i;
1523
1524	for (i = 0; i < BH_LRU_SIZE; i++) {
1525	brelse(b->bhs[i]);
1526	b->bhs[i] = NULL;
1527	}
1528	}
1529	/*
1530	* invalidate_bh_lrus() is called rarely - but not only at unmount.
1531	* This doesn't race because it runs in each cpu either in irq
1532	* or with preempt disabled.
1533	*/
1534	static void invalidate_bh_lru(void *arg)
1535	{
1536	struct bh_lru *b = &get_cpu_var(bh_lrus);
1537
1538	__invalidate_bh_lrus(b);
1539	put_cpu_var(bh_lrus);
1540	}
1541
1542	bool has_bh_in_lru(int cpu, void *dummy)
1543	{
1544	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1545	int i;
1546
1547	for (i = 0; i < BH_LRU_SIZE; i++) {
1548	if (b->bhs[i])
1549	return true;
1550	}
1551
1552	return false;
1553	}
1554
1555	void invalidate_bh_lrus(void)
1556	{
1557	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1);
1558	}
1559	EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1560
1561	/*
1562	* It's called from workqueue context so we need a bh_lru_lock to close
1563	* the race with preemption/irq.
1564	*/
1565	void invalidate_bh_lrus_cpu(void)
1566	{
1567	struct bh_lru *b;
1568
1569	bh_lru_lock();
1570	b = this_cpu_ptr(&bh_lrus);
1571	__invalidate_bh_lrus(b);
1572	bh_lru_unlock();
1573	}
1574
1575	void folio_set_bh(struct buffer_head bh, struct folio folio,
1576	unsigned long offset)
1577	{
1578	bh->b_folio = folio;
1579	BUG_ON(offset >= folio_size(folio));
1580	if (folio_test_highmem(folio))
1581	/*
1582	* This catches illegal uses and preserves the offset:
1583	*/
1584	bh->b_data = (char *)(0 + offset);
1585	else
1586	bh->b_data = folio_address(folio) + offset;
1587	}
1588	EXPORT_SYMBOL(folio_set_bh);
1589
1590	/*
1591	* Called when truncating a buffer on a page completely.
1592	*/
1593
1594	/* Bits that are cleared during an invalidate */
1595	#define BUFFER_FLAGS_DISCARD \
1596	(1 << BH_Mapped \| 1 << BH_New \| 1 << BH_Req \| \
1597	1 << BH_Delay \| 1 << BH_Unwritten)
1598
1599	static void discard_buffer(struct buffer_head * bh)
1600	{
1601	unsigned long b_state;
1602
1603	lock_buffer(bh);
1604	clear_buffer_dirty(bh);
1605	bh->b_bdev = NULL;
1606	b_state = READ_ONCE(bh->b_state);
1607	do {
1608	} while (!try_cmpxchg_relaxed(&bh->b_state, &b_state,
1609	b_state & ~BUFFER_FLAGS_DISCARD));
1610	unlock_buffer(bh);
1611	}
1612
1613	/**
1614	* block_invalidate_folio - Invalidate part or all of a buffer-backed folio.
1615	* @folio: The folio which is affected.
1616	* @offset: start of the range to invalidate
1617	* @length: length of the range to invalidate
1618	*
1619	* block_invalidate_folio() is called when all or part of the folio has been
1620	* invalidated by a truncate operation.
1621	*
1622	* block_invalidate_folio() does not have to release all buffers, but it must
1623	* ensure that no dirty buffer is left outside @offset and that no I/O
1624	* is underway against any of the blocks which are outside the truncation
1625	* point. Because the caller is about to free (and possibly reuse) those
1626	* blocks on-disk.
1627	*/
1628	void block_invalidate_folio(struct folio *folio, size_t offset, size_t length)
1629	{
1630	struct buffer_head head, bh, *next;
1631	size_t curr_off = 0;
1632	size_t stop = length + offset;
1633
1634	BUG_ON(!folio_test_locked(folio));
1635
1636	/*
1637	* Check for overflow
1638	*/
1639	BUG_ON(stop > folio_size(folio) \|\| stop < length);
1640
1641	head = folio_buffers(folio);
1642	if (!head)
1643	return;
1644
1645	bh = head;
1646	do {
1647	size_t next_off = curr_off + bh->b_size;
1648	next = bh->b_this_page;
1649
1650	/*
1651	* Are we still fully in range ?
1652	*/
1653	if (next_off > stop)
1654	goto out;
1655
1656	/*
1657	* is this block fully invalidated?
1658	*/
1659	if (offset <= curr_off)
1660	discard_buffer(bh);
1661	curr_off = next_off;
1662	bh = next;
1663	} while (bh != head);
1664
1665	/*
1666	* We release buffers only if the entire folio is being invalidated.
1667	* The get_block cached value has been unconditionally invalidated,
1668	* so real IO is not possible anymore.
1669	*/
1670	if (length == folio_size(folio))
1671	filemap_release_folio(folio, 0);
1672	out:
1673	folio_clear_mappedtodisk(folio);
1674	}
1675	EXPORT_SYMBOL(block_invalidate_folio);
1676
1677	/*
1678	* We attach and possibly dirty the buffers atomically wrt
1679	* block_dirty_folio() via i_private_lock. try_to_free_buffers
1680	* is already excluded via the folio lock.
1681	*/
1682	struct buffer_head create_empty_buffers(struct folio folio,
1683	unsigned long blocksize, unsigned long b_state)
1684	{
1685	struct buffer_head bh, head, *tail;
1686	gfp_t gfp = GFP_NOFS \| __GFP_ACCOUNT \| __GFP_NOFAIL;
1687
1688	head = folio_alloc_buffers(folio, blocksize, gfp);
1689	bh = head;
1690	do {
1691	bh->b_state \|= b_state;
1692	tail = bh;
1693	bh = bh->b_this_page;
1694	} while (bh);
1695	tail->b_this_page = head;
1696
1697	spin_lock(&folio->mapping->i_private_lock);
1698	if (folio_test_uptodate(folio) \|\| folio_test_dirty(folio)) {
1699	bh = head;
1700	do {
1701	if (folio_test_dirty(folio))
1702	set_buffer_dirty(bh);
1703	if (folio_test_uptodate(folio))
1704	set_buffer_uptodate(bh);
1705	bh = bh->b_this_page;
1706	} while (bh != head);
1707	}
1708	folio_attach_private(folio, head);
1709	spin_unlock(&folio->mapping->i_private_lock);
1710
1711	return head;
1712	}
1713	EXPORT_SYMBOL(create_empty_buffers);
1714
1715	/**
1716	* clean_bdev_aliases: clean a range of buffers in block device
1717	* @bdev: Block device to clean buffers in
1718	* @block: Start of a range of blocks to clean
1719	* @len: Number of blocks to clean
1720	*
1721	* We are taking a range of blocks for data and we don't want writeback of any
1722	* buffer-cache aliases starting from return from this function and until the
1723	* moment when something will explicitly mark the buffer dirty (hopefully that
1724	* will not happen until we will free that block ;-) We don't even need to mark
1725	* it not-uptodate - nobody can expect anything from a newly allocated buffer
1726	* anyway. We used to use unmap_buffer() for such invalidation, but that was
1727	* wrong. We definitely don't want to mark the alias unmapped, for example - it
1728	* would confuse anyone who might pick it with bread() afterwards...
1729	*
1730	* Also.. Note that bforget() doesn't lock the buffer. So there can be
1731	* writeout I/O going on against recently-freed buffers. We don't wait on that
1732	* I/O in bforget() - it's more efficient to wait on the I/O only if we really
1733	* need to. That happens here.
1734	*/
1735	void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1736	{
1737	struct address_space *bd_mapping = bdev->bd_mapping;
1738	const int blkbits = bd_mapping->host->i_blkbits;
1739	struct folio_batch fbatch;
1740	pgoff_t index = ((loff_t)block << blkbits) / PAGE_SIZE;
1741	pgoff_t end;
1742	int i, count;
1743	struct buffer_head *bh;
1744	struct buffer_head *head;
1745
1746	end = ((loff_t)(block + len - 1) << blkbits) / PAGE_SIZE;
1747	folio_batch_init(&fbatch);
1748	while (filemap_get_folios(bd_mapping, &index, end, &fbatch)) {
1749	count = folio_batch_count(&fbatch);
1750	for (i = 0; i < count; i++) {
1751	struct folio *folio = fbatch.folios[i];
1752
1753	if (!folio_buffers(folio))
1754	continue;
1755	/*
1756	* We use folio lock instead of bd_mapping->i_private_lock
1757	* to pin buffers here since we can afford to sleep and
1758	* it scales better than a global spinlock lock.
1759	*/
1760	folio_lock(folio);
1761	/* Recheck when the folio is locked which pins bhs */
1762	head = folio_buffers(folio);
1763	if (!head)
1764	goto unlock_page;
1765	bh = head;
1766	do {
1767	if (!buffer_mapped(bh) \|\| (bh->b_blocknr < block))
1768	goto next;
1769	if (bh->b_blocknr >= block + len)
1770	break;
1771	clear_buffer_dirty(bh);
1772	wait_on_buffer(bh);
1773	clear_buffer_req(bh);
1774	next:
1775	bh = bh->b_this_page;
1776	} while (bh != head);
1777	unlock_page:
1778	folio_unlock(folio);
1779	}
1780	folio_batch_release(&fbatch);
1781	cond_resched();
1782	/* End of range already reached? */
1783	if (index > end \|\| !index)
1784	break;
1785	}
1786	}
1787	EXPORT_SYMBOL(clean_bdev_aliases);
1788
1789	static struct buffer_head folio_create_buffers(struct folio folio,
1790	struct inode *inode,
1791	unsigned int b_state)
1792	{
1793	struct buffer_head *bh;
1794
1795	BUG_ON(!folio_test_locked(folio));
1796
1797	bh = folio_buffers(folio);
1798	if (!bh)
1799	bh = create_empty_buffers(folio,
1800	1 << READ_ONCE(inode->i_blkbits), b_state);
1801	return bh;
1802	}
1803
1804	/*
1805	* NOTE! All mapped/uptodate combinations are valid:
1806	*
1807	* Mapped Uptodate Meaning
1808	*
1809	* No No "unknown" - must do get_block()
1810	* No Yes "hole" - zero-filled
1811	* Yes No "allocated" - allocated on disk, not read in
1812	* Yes Yes "valid" - allocated and up-to-date in memory.
1813	*
1814	* "Dirty" is valid only with the last case (mapped+uptodate).
1815	*/
1816
1817	/*
1818	* While block_write_full_folio is writing back the dirty buffers under
1819	* the page lock, whoever dirtied the buffers may decide to clean them
1820	* again at any time. We handle that by only looking at the buffer
1821	* state inside lock_buffer().
1822	*
1823	* If block_write_full_folio() is called for regular writeback
1824	* (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1825	* locked buffer. This only can happen if someone has written the buffer
1826	* directly, with submit_bh(). At the address_space level PageWriteback
1827	* prevents this contention from occurring.
1828	*
1829	* If block_write_full_folio() is called with wbc->sync_mode ==
1830	* WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1831	* causes the writes to be flagged as synchronous writes.
1832	*/
1833	int __block_write_full_folio(struct inode inode, struct folio folio,
1834	get_block_t get_block, struct writeback_control wbc)
1835	{
1836	int err;
1837	sector_t block;
1838	sector_t last_block;
1839	struct buffer_head bh, head;
1840	size_t blocksize;
1841	int nr_underway = 0;
1842	blk_opf_t write_flags = wbc_to_write_flags(wbc);
1843
1844	head = folio_create_buffers(folio, inode,
1845	(1 << BH_Dirty) \| (1 << BH_Uptodate));
1846
1847	/*
1848	* Be very careful. We have no exclusion from block_dirty_folio
1849	* here, and the (potentially unmapped) buffers may become dirty at
1850	* any time. If a buffer becomes dirty here after we've inspected it
1851	* then we just miss that fact, and the folio stays dirty.
1852	*
1853	* Buffers outside i_size may be dirtied by block_dirty_folio;
1854	* handle that here by just cleaning them.
1855	*/
1856
1857	bh = head;
1858	blocksize = bh->b_size;
1859
1860	block = div_u64(folio_pos(folio), blocksize);
1861	last_block = div_u64(i_size_read(inode) - 1, blocksize);
1862
1863	/*
1864	* Get all the dirty buffers mapped to disk addresses and
1865	* handle any aliases from the underlying blockdev's mapping.
1866	*/
1867	do {
1868	if (block > last_block) {
1869	/*
1870	* mapped buffers outside i_size will occur, because
1871	* this folio can be outside i_size when there is a
1872	* truncate in progress.
1873	*/
1874	/*
1875	* The buffer was zeroed by block_write_full_folio()
1876	*/
1877	clear_buffer_dirty(bh);
1878	set_buffer_uptodate(bh);
1879	} else if ((!buffer_mapped(bh) \|\| buffer_delay(bh)) &&
1880	buffer_dirty(bh)) {
1881	WARN_ON(bh->b_size != blocksize);
1882	err = get_block(inode, block, bh, 1);
1883	if (err)
1884	goto recover;
1885	clear_buffer_delay(bh);
1886	if (buffer_new(bh)) {
1887	/* blockdev mappings never come here */
1888	clear_buffer_new(bh);
1889	clean_bdev_bh_alias(bh);
1890	}
1891	}
1892	bh = bh->b_this_page;
1893	block++;
1894	} while (bh != head);
1895
1896	do {
1897	if (!buffer_mapped(bh))
1898	continue;
1899	/*
1900	* If it's a fully non-blocking write attempt and we cannot
1901	* lock the buffer then redirty the folio. Note that this can
1902	* potentially cause a busy-wait loop from writeback threads
1903	* and kswapd activity, but those code paths have their own
1904	* higher-level throttling.
1905	*/
1906	if (wbc->sync_mode != WB_SYNC_NONE) {
1907	lock_buffer(bh);
1908	} else if (!trylock_buffer(bh)) {
1909	folio_redirty_for_writepage(wbc, folio);
1910	continue;
1911	}
1912	if (test_clear_buffer_dirty(bh)) {
1913	mark_buffer_async_write_endio(bh,
1914	end_buffer_async_write);
1915	} else {
1916	unlock_buffer(bh);
1917	}
1918	} while ((bh = bh->b_this_page) != head);
1919
1920	/*
1921	* The folio and its buffers are protected by the writeback flag,
1922	* so we can drop the bh refcounts early.
1923	*/
1924	BUG_ON(folio_test_writeback(folio));
1925	folio_start_writeback(folio);
1926
1927	do {
1928	struct buffer_head *next = bh->b_this_page;
1929	if (buffer_async_write(bh)) {
1930	submit_bh_wbc(REQ_OP_WRITE \| write_flags, bh,
1931	inode->i_write_hint, wbc);
1932	nr_underway++;
1933	}
1934	bh = next;
1935	} while (bh != head);
1936	folio_unlock(folio);
1937
1938	err = 0;
1939	done:
1940	if (nr_underway == 0) {
1941	/*
1942	* The folio was marked dirty, but the buffers were
1943	* clean. Someone wrote them back by hand with
1944	* write_dirty_buffer/submit_bh. A rare case.
1945	*/
1946	folio_end_writeback(folio);
1947
1948	/*
1949	* The folio and buffer_heads can be released at any time from
1950	* here on.
1951	*/
1952	}
1953	return err;
1954
1955	recover:
1956	/*
1957	* ENOSPC, or some other error. We may already have added some
1958	* blocks to the file, so we need to write these out to avoid
1959	* exposing stale data.
1960	* The folio is currently locked and not marked for writeback
1961	*/
1962	bh = head;
1963	/* Recovery: lock and submit the mapped buffers */
1964	do {
1965	if (buffer_mapped(bh) && buffer_dirty(bh) &&
1966	!buffer_delay(bh)) {
1967	lock_buffer(bh);
1968	mark_buffer_async_write_endio(bh,
1969	end_buffer_async_write);
1970	} else {
1971	/*
1972	* The buffer may have been set dirty during
1973	* attachment to a dirty folio.
1974	*/
1975	clear_buffer_dirty(bh);
1976	}
1977	} while ((bh = bh->b_this_page) != head);
1978	BUG_ON(folio_test_writeback(folio));
1979	mapping_set_error(folio->mapping, err);
1980	folio_start_writeback(folio);
1981	do {
1982	struct buffer_head *next = bh->b_this_page;
1983	if (buffer_async_write(bh)) {
1984	clear_buffer_dirty(bh);
1985	submit_bh_wbc(REQ_OP_WRITE \| write_flags, bh,
1986	inode->i_write_hint, wbc);
1987	nr_underway++;
1988	}
1989	bh = next;
1990	} while (bh != head);
1991	folio_unlock(folio);
1992	goto done;
1993	}
1994	EXPORT_SYMBOL(__block_write_full_folio);
1995
1996	/*
1997	* If a folio has any new buffers, zero them out here, and mark them uptodate
1998	* and dirty so they'll be written out (in order to prevent uninitialised
1999	* block data from leaking). And clear the new bit.
2000	*/
2001	void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to)
2002	{
2003	size_t block_start, block_end;
2004	struct buffer_head head, bh;
2005
2006	BUG_ON(!folio_test_locked(folio));
2007	head = folio_buffers(folio);
2008	if (!head)
2009	return;
2010
2011	bh = head;
2012	block_start = 0;
2013	do {
2014	block_end = block_start + bh->b_size;
2015
2016	if (buffer_new(bh)) {
2017	if (block_end > from && block_start < to) {
2018	if (!folio_test_uptodate(folio)) {
2019	size_t start, xend;
2020
2021	start = max(from, block_start);
2022	xend = min(to, block_end);
2023
2024	folio_zero_segment(folio, start, xend);
2025	set_buffer_uptodate(bh);
2026	}
2027
2028	clear_buffer_new(bh);
2029	mark_buffer_dirty(bh);
2030	}
2031	}
2032
2033	block_start = block_end;
2034	bh = bh->b_this_page;
2035	} while (bh != head);
2036	}
2037	EXPORT_SYMBOL(folio_zero_new_buffers);
2038
2039	static int
2040	iomap_to_bh(struct inode inode, sector_t block, struct buffer_head bh,
2041	const struct iomap *iomap)
2042	{
2043	loff_t offset = (loff_t)block << inode->i_blkbits;
2044
2045	bh->b_bdev = iomap->bdev;
2046
2047	/*
2048	* Block points to offset in file we need to map, iomap contains
2049	* the offset at which the map starts. If the map ends before the
2050	* current block, then do not map the buffer and let the caller
2051	* handle it.
2052	*/
2053	if (offset >= iomap->offset + iomap->length)
2054	return -EIO;
2055
2056	switch (iomap->type) {
2057	case IOMAP_HOLE:
2058	/*
2059	* If the buffer is not up to date or beyond the current EOF,
2060	* we need to mark it as new to ensure sub-block zeroing is
2061	* executed if necessary.
2062	*/
2063	if (!buffer_uptodate(bh) \|\|
2064	(offset >= i_size_read(inode)))
2065	set_buffer_new(bh);
2066	return 0;
2067	case IOMAP_DELALLOC:
2068	if (!buffer_uptodate(bh) \|\|
2069	(offset >= i_size_read(inode)))
2070	set_buffer_new(bh);
2071	set_buffer_uptodate(bh);
2072	set_buffer_mapped(bh);
2073	set_buffer_delay(bh);
2074	return 0;
2075	case IOMAP_UNWRITTEN:
2076	/*
2077	* For unwritten regions, we always need to ensure that regions
2078	* in the block we are not writing to are zeroed. Mark the
2079	* buffer as new to ensure this.
2080	*/
2081	set_buffer_new(bh);
2082	set_buffer_unwritten(bh);
2083	fallthrough;
2084	case IOMAP_MAPPED:
2085	if ((iomap->flags & IOMAP_F_NEW) \|\|
2086	offset >= i_size_read(inode)) {
2087	/*
2088	* This can happen if truncating the block device races
2089	* with the check in the caller as i_size updates on
2090	* block devices aren't synchronized by i_rwsem for
2091	* block devices.
2092	*/
2093	if (S_ISBLK(inode->i_mode))
2094	return -EIO;
2095	set_buffer_new(bh);
2096	}
2097	bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
2098	inode->i_blkbits;
2099	set_buffer_mapped(bh);
2100	return 0;
2101	default:
2102	WARN_ON_ONCE(1);
2103	return -EIO;
2104	}
2105	}
2106
2107	int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len,
2108	get_block_t get_block, const struct iomap iomap)
2109	{
2110	size_t from = offset_in_folio(folio, pos);
2111	size_t to = from + len;
2112	struct inode *inode = folio->mapping->host;
2113	size_t block_start, block_end;
2114	sector_t block;
2115	int err = 0;
2116	size_t blocksize;
2117	struct buffer_head bh, head, wait[2], *wait_bh=wait;
2118
2119	BUG_ON(!folio_test_locked(folio));
2120	BUG_ON(to > folio_size(folio));
2121	BUG_ON(from > to);
2122
2123	head = folio_create_buffers(folio, inode, 0);
2124	blocksize = head->b_size;
2125	block = div_u64(folio_pos(folio), blocksize);
2126
2127	for (bh = head, block_start = 0; bh != head \|\| !block_start;
2128	block++, block_start=block_end, bh = bh->b_this_page) {
2129	block_end = block_start + blocksize;
2130	if (block_end <= from \|\| block_start >= to) {
2131	if (folio_test_uptodate(folio)) {
2132	if (!buffer_uptodate(bh))
2133	set_buffer_uptodate(bh);
2134	}
2135	continue;
2136	}
2137	if (buffer_new(bh))
2138	clear_buffer_new(bh);
2139	if (!buffer_mapped(bh)) {
2140	WARN_ON(bh->b_size != blocksize);
2141	if (get_block)
2142	err = get_block(inode, block, bh, 1);
2143	else
2144	err = iomap_to_bh(inode, block, bh, iomap);
2145	if (err)
2146	break;
2147
2148	if (buffer_new(bh)) {
2149	clean_bdev_bh_alias(bh);
2150	if (folio_test_uptodate(folio)) {
2151	clear_buffer_new(bh);
2152	set_buffer_uptodate(bh);
2153	mark_buffer_dirty(bh);
2154	continue;
2155	}
2156	if (block_end > to \|\| block_start < from)
2157	folio_zero_segments(folio,
2158	to, block_end,
2159	block_start, from);
2160	continue;
2161	}
2162	}
2163	if (folio_test_uptodate(folio)) {
2164	if (!buffer_uptodate(bh))
2165	set_buffer_uptodate(bh);
2166	continue;
2167	}
2168	if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2169	!buffer_unwritten(bh) &&
2170	(block_start < from \|\| block_end > to)) {
2171	bh_read_nowait(bh, 0);
2172	*wait_bh++=bh;
2173	}
2174	}
2175	/*
2176	* If we issued read requests - let them complete.
2177	*/
2178	while(wait_bh > wait) {
2179	wait_on_buffer(*--wait_bh);
2180	if (!buffer_uptodate(*wait_bh))
2181	err = -EIO;
2182	}
2183	if (unlikely(err))
2184	folio_zero_new_buffers(folio, from, to);
2185	return err;
2186	}
2187
2188	int __block_write_begin(struct folio *folio, loff_t pos, unsigned len,
2189	get_block_t *get_block)
2190	{
2191	return __block_write_begin_int(folio, pos, len, get_block, NULL);
2192	}
2193	EXPORT_SYMBOL(__block_write_begin);
2194
2195	void block_commit_write(struct folio *folio, size_t from, size_t to)
2196	{
2197	size_t block_start, block_end;
2198	bool partial = false;
2199	unsigned blocksize;
2200	struct buffer_head bh, head;
2201
2202	bh = head = folio_buffers(folio);
2203	if (!bh)
2204	return;
2205	blocksize = bh->b_size;
2206
2207	block_start = 0;
2208	do {
2209	block_end = block_start + blocksize;
2210	if (block_end <= from \|\| block_start >= to) {
2211	if (!buffer_uptodate(bh))
2212	partial = true;
2213	} else {
2214	set_buffer_uptodate(bh);
2215	mark_buffer_dirty(bh);
2216	}
2217	if (buffer_new(bh))
2218	clear_buffer_new(bh);
2219
2220	block_start = block_end;
2221	bh = bh->b_this_page;
2222	} while (bh != head);
2223
2224	/*
2225	* If this is a partial write which happened to make all buffers
2226	* uptodate then we can optimize away a bogus read_folio() for
2227	* the next read(). Here we 'discover' whether the folio went
2228	* uptodate as a result of this (potentially partial) write.
2229	*/
2230	if (!partial)
2231	folio_mark_uptodate(folio);
2232	}
2233	EXPORT_SYMBOL(block_commit_write);
2234
2235	/*
2236	* block_write_begin takes care of the basic task of block allocation and
2237	* bringing partial write blocks uptodate first.
2238	*
2239	* The filesystem needs to handle block truncation upon failure.
2240	*/
2241	int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2242	struct folio *foliop, get_block_t get_block)
2243	{
2244	pgoff_t index = pos >> PAGE_SHIFT;
2245	struct folio *folio;
2246	int status;
2247
2248	folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
2249	mapping_gfp_mask(mapping));
2250	if (IS_ERR(folio))
2251	return PTR_ERR(folio);
2252
2253	status = __block_write_begin_int(folio, pos, len, get_block, NULL);
2254	if (unlikely(status)) {
2255	folio_unlock(folio);
2256	folio_put(folio);
2257	folio = NULL;
2258	}
2259
2260	*foliop = folio;
2261	return status;
2262	}
2263	EXPORT_SYMBOL(block_write_begin);
2264
2265	int block_write_end(loff_t pos, unsigned len, unsigned copied,
2266	struct folio *folio)
2267	{
2268	size_t start = pos - folio_pos(folio);
2269
2270	if (unlikely(copied < len)) {
2271	/*
2272	* The buffers that were written will now be uptodate, so
2273	* we don't have to worry about a read_folio reading them
2274	* and overwriting a partial write. However if we have
2275	* encountered a short write and only partially written
2276	* into a buffer, it will not be marked uptodate, so a
2277	* read_folio might come in and destroy our partial write.
2278	*
2279	* Do the simplest thing, and just treat any short write to a
2280	* non uptodate folio as a zero-length write, and force the
2281	* caller to redo the whole thing.
2282	*/
2283	if (!folio_test_uptodate(folio))
2284	copied = 0;
2285
2286	folio_zero_new_buffers(folio, start+copied, start+len);
2287	}
2288	flush_dcache_folio(folio);
2289
2290	/* This could be a short (even 0-length) commit */
2291	block_commit_write(folio, start, start + copied);
2292
2293	return copied;
2294	}
2295	EXPORT_SYMBOL(block_write_end);
2296
2297	int generic_write_end(const struct kiocb iocb, struct address_space mapping,
2298	loff_t pos, unsigned len, unsigned copied,
2299	struct folio folio, void fsdata)
2300	{
2301	struct inode *inode = mapping->host;
2302	loff_t old_size = inode->i_size;
2303	bool i_size_changed = false;
2304
2305	copied = block_write_end(pos, len, copied, folio);
2306
2307	/*
2308	* No need to use i_size_read() here, the i_size cannot change under us
2309	* because we hold i_rwsem.
2310	*
2311	* But it's important to update i_size while still holding folio lock:
2312	* page writeout could otherwise come in and zero beyond i_size.
2313	*/
2314	if (pos + copied > inode->i_size) {
2315	i_size_write(inode, pos + copied);
2316	i_size_changed = true;
2317	}
2318
2319	folio_unlock(folio);
2320	folio_put(folio);
2321
2322	if (old_size < pos)
2323	pagecache_isize_extended(inode, old_size, pos);
2324	/*
2325	* Don't mark the inode dirty under page lock. First, it unnecessarily
2326	* makes the holding time of page lock longer. Second, it forces lock
2327	* ordering of page lock and transaction start for journaling
2328	* filesystems.
2329	*/
2330	if (i_size_changed)
2331	mark_inode_dirty(inode);
2332	return copied;
2333	}
2334	EXPORT_SYMBOL(generic_write_end);
2335
2336	/*
2337	* block_is_partially_uptodate checks whether buffers within a folio are
2338	* uptodate or not.
2339	*
2340	* Returns true if all buffers which correspond to the specified part
2341	* of the folio are uptodate.
2342	*/
2343	bool block_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
2344	{
2345	unsigned block_start, block_end, blocksize;
2346	unsigned to;
2347	struct buffer_head bh, head;
2348	bool ret = true;
2349
2350	head = folio_buffers(folio);
2351	if (!head)
2352	return false;
2353	blocksize = head->b_size;
2354	to = min(folio_size(folio) - from, count);
2355	to = from + to;
2356	if (from < blocksize && to > folio_size(folio) - blocksize)
2357	return false;
2358
2359	bh = head;
2360	block_start = 0;
2361	do {
2362	block_end = block_start + blocksize;
2363	if (block_end > from && block_start < to) {
2364	if (!buffer_uptodate(bh)) {
2365	ret = false;
2366	break;
2367	}
2368	if (block_end >= to)
2369	break;
2370	}
2371	block_start = block_end;
2372	bh = bh->b_this_page;
2373	} while (bh != head);
2374
2375	return ret;
2376	}
2377	EXPORT_SYMBOL(block_is_partially_uptodate);
2378
2379	/*
2380	* Generic "read_folio" function for block devices that have the normal
2381	* get_block functionality. This is most of the block device filesystems.
2382	* Reads the folio asynchronously --- the unlock_buffer() and
2383	* set/clear_buffer_uptodate() functions propagate buffer state into the
2384	* folio once IO has completed.
2385	*/
2386	int block_read_full_folio(struct folio folio, get_block_t get_block)
2387	{
2388	struct inode *inode = folio->mapping->host;
2389	sector_t iblock, lblock;
2390	struct buffer_head bh, head, *prev = NULL;
2391	size_t blocksize;
2392	int fully_mapped = 1;
2393	bool page_error = false;
2394	loff_t limit = i_size_read(inode);
2395
2396	/* This is needed for ext4. */
2397	if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
2398	limit = inode->i_sb->s_maxbytes;
2399
2400	head = folio_create_buffers(folio, inode, 0);
2401	blocksize = head->b_size;
2402
2403	iblock = div_u64(folio_pos(folio), blocksize);
2404	lblock = div_u64(limit + blocksize - 1, blocksize);
2405	bh = head;
2406
2407	do {
2408	if (buffer_uptodate(bh))
2409	continue;
2410
2411	if (!buffer_mapped(bh)) {
2412	int err = 0;
2413
2414	fully_mapped = 0;
2415	if (iblock < lblock) {
2416	WARN_ON(bh->b_size != blocksize);
2417	err = get_block(inode, iblock, bh, 0);
2418	if (err)
2419	page_error = true;
2420	}
2421	if (!buffer_mapped(bh)) {
2422	folio_zero_range(folio, bh_offset(bh),
2423	blocksize);
2424	if (!err)
2425	set_buffer_uptodate(bh);
2426	continue;
2427	}
2428	/*
2429	* get_block() might have updated the buffer
2430	* synchronously
2431	*/
2432	if (buffer_uptodate(bh))
2433	continue;
2434	}
2435
2436	lock_buffer(bh);
2437	if (buffer_uptodate(bh)) {
2438	unlock_buffer(bh);
2439	continue;
2440	}
2441
2442	mark_buffer_async_read(bh);
2443	if (prev)
2444	submit_bh(REQ_OP_READ, prev);
2445	prev = bh;
2446	} while (iblock++, (bh = bh->b_this_page) != head);
2447
2448	if (fully_mapped)
2449	folio_set_mappedtodisk(folio);
2450
2451	/*
2452	* All buffers are uptodate or get_block() returned an error
2453	* when trying to map them - we must finish the read because
2454	* end_buffer_async_read() will never be called on any buffer
2455	* in this folio.
2456	*/
2457	if (prev)
2458	submit_bh(REQ_OP_READ, prev);
2459	else
2460	folio_end_read(folio, !page_error);
2461
2462	return 0;
2463	}
2464	EXPORT_SYMBOL(block_read_full_folio);
2465
2466	/* utility function for filesystems that need to do work on expanding
2467	* truncates. Uses filesystem pagecache writes to allow the filesystem to
2468	* deal with the hole.
2469	*/
2470	int generic_cont_expand_simple(struct inode *inode, loff_t size)
2471	{
2472	struct address_space *mapping = inode->i_mapping;
2473	const struct address_space_operations *aops = mapping->a_ops;
2474	struct folio *folio;
2475	void *fsdata = NULL;
2476	int err;
2477
2478	err = inode_newsize_ok(inode, size);
2479	if (err)
2480	goto out;
2481
2482	err = aops->write_begin(NULL, mapping, size, 0, &folio, &fsdata);
2483	if (err)
2484	goto out;
2485
2486	err = aops->write_end(NULL, mapping, size, 0, 0, folio, fsdata);
2487	BUG_ON(err > 0);
2488
2489	out:
2490	return err;
2491	}
2492	EXPORT_SYMBOL(generic_cont_expand_simple);
2493
2494	static int cont_expand_zero(const struct kiocb *iocb,
2495	struct address_space *mapping,
2496	loff_t pos, loff_t *bytes)
2497	{
2498	struct inode *inode = mapping->host;
2499	const struct address_space_operations *aops = mapping->a_ops;
2500	unsigned int blocksize = i_blocksize(inode);
2501	struct folio *folio;
2502	void *fsdata = NULL;
2503	pgoff_t index, curidx;
2504	loff_t curpos;
2505	unsigned zerofrom, offset, len;
2506	int err = 0;
2507
2508	index = pos >> PAGE_SHIFT;
2509	offset = pos & ~PAGE_MASK;
2510
2511	while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2512	zerofrom = curpos & ~PAGE_MASK;
2513	if (zerofrom & (blocksize-1)) {
2514	*bytes \|= (blocksize-1);
2515	(*bytes)++;
2516	}
2517	len = PAGE_SIZE - zerofrom;
2518
2519	err = aops->write_begin(iocb, mapping, curpos, len,
2520	&folio, &fsdata);
2521	if (err)
2522	goto out;
2523	folio_zero_range(folio, offset_in_folio(folio, curpos), len);
2524	err = aops->write_end(iocb, mapping, curpos, len, len,
2525	folio, fsdata);
2526	if (err < 0)
2527	goto out;
2528	BUG_ON(err != len);
2529	err = 0;
2530
2531	balance_dirty_pages_ratelimited(mapping);
2532
2533	if (fatal_signal_pending(current)) {
2534	err = -EINTR;
2535	goto out;
2536	}
2537	}
2538
2539	/* page covers the boundary, find the boundary offset */
2540	if (index == curidx) {
2541	zerofrom = curpos & ~PAGE_MASK;
2542	/* if we will expand the thing last block will be filled */
2543	if (offset <= zerofrom) {
2544	goto out;
2545	}
2546	if (zerofrom & (blocksize-1)) {
2547	*bytes \|= (blocksize-1);
2548	(*bytes)++;
2549	}
2550	len = offset - zerofrom;
2551
2552	err = aops->write_begin(iocb, mapping, curpos, len,
2553	&folio, &fsdata);
2554	if (err)
2555	goto out;
2556	folio_zero_range(folio, offset_in_folio(folio, curpos), len);
2557	err = aops->write_end(iocb, mapping, curpos, len, len,
2558	folio, fsdata);
2559	if (err < 0)
2560	goto out;
2561	BUG_ON(err != len);
2562	err = 0;
2563	}
2564	out:
2565	return err;
2566	}
2567
2568	/*
2569	* For moronic filesystems that do not allow holes in file.
2570	* We may have to extend the file.
2571	*/
2572	int cont_write_begin(const struct kiocb iocb, struct address_space mapping,
2573	loff_t pos, unsigned len, struct folio **foliop,
2574	void *fsdata, get_block_t get_block, loff_t *bytes)
2575	{
2576	struct inode *inode = mapping->host;
2577	unsigned int blocksize = i_blocksize(inode);
2578	unsigned int zerofrom;
2579	int err;
2580
2581	err = cont_expand_zero(iocb, mapping, pos, bytes);
2582	if (err)
2583	return err;
2584
2585	zerofrom = *bytes & ~PAGE_MASK;
2586	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2587	*bytes \|= (blocksize-1);
2588	(*bytes)++;
2589	}
2590
2591	return block_write_begin(mapping, pos, len, foliop, get_block);
2592	}
2593	EXPORT_SYMBOL(cont_write_begin);
2594
2595	/*
2596	* block_page_mkwrite() is not allowed to change the file size as it gets
2597	* called from a page fault handler when a page is first dirtied. Hence we must
2598	* be careful to check for EOF conditions here. We set the page up correctly
2599	* for a written page which means we get ENOSPC checking when writing into
2600	* holes and correct delalloc and unwritten extent mapping on filesystems that
2601	* support these features.
2602	*
2603	* We are not allowed to take the i_rwsem here so we have to play games to
2604	* protect against truncate races as the page could now be beyond EOF. Because
2605	* truncate writes the inode size before removing pages, once we have the
2606	* page lock we can determine safely if the page is beyond EOF. If it is not
2607	* beyond EOF, then the page is guaranteed safe against truncation until we
2608	* unlock the page.
2609	*
2610	* Direct callers of this function should protect against filesystem freezing
2611	* using sb_start_pagefault() - sb_end_pagefault() functions.
2612	*/
2613	int block_page_mkwrite(struct vm_area_struct vma, struct vm_fault vmf,
2614	get_block_t get_block)
2615	{
2616	struct folio *folio = page_folio(vmf->page);
2617	struct inode *inode = file_inode(vma->vm_file);
2618	unsigned long end;
2619	loff_t size;
2620	int ret;
2621
2622	folio_lock(folio);
2623	size = i_size_read(inode);
2624	if ((folio->mapping != inode->i_mapping) \|\|
2625	(folio_pos(folio) >= size)) {
2626	/* We overload EFAULT to mean page got truncated */
2627	ret = -EFAULT;
2628	goto out_unlock;
2629	}
2630
2631	end = folio_size(folio);
2632	/* folio is wholly or partially inside EOF */
2633	if (folio_pos(folio) + end > size)
2634	end = size - folio_pos(folio);
2635
2636	ret = __block_write_begin_int(folio, 0, end, get_block, NULL);
2637	if (unlikely(ret))
2638	goto out_unlock;
2639
2640	block_commit_write(folio, 0, end);
2641
2642	folio_mark_dirty(folio);
2643	folio_wait_stable(folio);
2644	return 0;
2645	out_unlock:
2646	folio_unlock(folio);
2647	return ret;
2648	}
2649	EXPORT_SYMBOL(block_page_mkwrite);
2650
2651	int block_truncate_page(struct address_space *mapping,
2652	loff_t from, get_block_t *get_block)
2653	{
2654	pgoff_t index = from >> PAGE_SHIFT;
2655	unsigned blocksize;
2656	sector_t iblock;
2657	size_t offset, length, pos;
2658	struct inode *inode = mapping->host;
2659	struct folio *folio;
2660	struct buffer_head *bh;
2661	int err = 0;
2662
2663	blocksize = i_blocksize(inode);
2664	length = from & (blocksize - 1);
2665
2666	/* Block boundary? Nothing to do */
2667	if (!length)
2668	return 0;
2669
2670	length = blocksize - length;
2671	iblock = ((loff_t)index * PAGE_SIZE) >> inode->i_blkbits;
2672
2673	folio = filemap_grab_folio(mapping, index);
2674	if (IS_ERR(folio))
2675	return PTR_ERR(folio);
2676
2677	bh = folio_buffers(folio);
2678	if (!bh)
2679	bh = create_empty_buffers(folio, blocksize, 0);
2680
2681	/* Find the buffer that contains "offset" */
2682	offset = offset_in_folio(folio, from);
2683	pos = blocksize;
2684	while (offset >= pos) {
2685	bh = bh->b_this_page;
2686	iblock++;
2687	pos += blocksize;
2688	}
2689
2690	if (!buffer_mapped(bh)) {
2691	WARN_ON(bh->b_size != blocksize);
2692	err = get_block(inode, iblock, bh, 0);
2693	if (err)
2694	goto unlock;
2695	/* unmapped? It's a hole - nothing to do */
2696	if (!buffer_mapped(bh))
2697	goto unlock;
2698	}
2699
2700	/* Ok, it's mapped. Make sure it's up-to-date */
2701	if (folio_test_uptodate(folio))
2702	set_buffer_uptodate(bh);
2703
2704	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2705	err = bh_read(bh, 0);
2706	/* Uhhuh. Read error. Complain and punt. */
2707	if (err < 0)
2708	goto unlock;
2709	}
2710
2711	folio_zero_range(folio, offset, length);
2712	mark_buffer_dirty(bh);
2713
2714	unlock:
2715	folio_unlock(folio);
2716	folio_put(folio);
2717
2718	return err;
2719	}
2720	EXPORT_SYMBOL(block_truncate_page);
2721
2722	/*
2723	* The generic write folio function for buffer-backed address_spaces
2724	*/
2725	int block_write_full_folio(struct folio folio, struct writeback_control wbc,
2726	void *get_block)
2727	{
2728	struct inode * const inode = folio->mapping->host;
2729	loff_t i_size = i_size_read(inode);
2730
2731	/* Is the folio fully inside i_size? */
2732	if (folio_next_pos(folio) <= i_size)
2733	return __block_write_full_folio(inode, folio, get_block, wbc);
2734
2735	/* Is the folio fully outside i_size? (truncate in progress) */
2736	if (folio_pos(folio) >= i_size) {
2737	folio_unlock(folio);
2738	return 0; /* don't care */
2739	}
2740
2741	/*
2742	* The folio straddles i_size. It must be zeroed out on each and every
2743	* writeback invocation because it may be mmapped. "A file is mapped
2744	* in multiples of the page size. For a file that is not a multiple of
2745	* the page size, the remaining memory is zeroed when mapped, and
2746	* writes to that region are not written out to the file."
2747	*/
2748	folio_zero_segment(folio, offset_in_folio(folio, i_size),
2749	folio_size(folio));
2750	return __block_write_full_folio(inode, folio, get_block, wbc);
2751	}
2752
2753	sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2754	get_block_t *get_block)
2755	{
2756	struct inode *inode = mapping->host;
2757	struct buffer_head tmp = {
2758	.b_size = i_blocksize(inode),
2759	};
2760
2761	get_block(inode, block, &tmp, 0);
2762	return tmp.b_blocknr;
2763	}
2764	EXPORT_SYMBOL(generic_block_bmap);
2765
2766	static void end_bio_bh_io_sync(struct bio *bio)
2767	{
2768	struct buffer_head *bh = bio->bi_private;
2769
2770	if (unlikely(bio_flagged(bio, BIO_QUIET)))
2771	set_bit(BH_Quiet, &bh->b_state);
2772
2773	bh->b_end_io(bh, !bio->bi_status);
2774	bio_put(bio);
2775	}
2776
2777	static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
2778	enum rw_hint write_hint,
2779	struct writeback_control *wbc)
2780	{
2781	const enum req_op op = opf & REQ_OP_MASK;
2782	struct bio *bio;
2783
2784	BUG_ON(!buffer_locked(bh));
2785	BUG_ON(!buffer_mapped(bh));
2786	BUG_ON(!bh->b_end_io);
2787	BUG_ON(buffer_delay(bh));
2788	BUG_ON(buffer_unwritten(bh));
2789
2790	/*
2791	* Only clear out a write error when rewriting
2792	*/
2793	if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
2794	clear_buffer_write_io_error(bh);
2795
2796	if (buffer_meta(bh))
2797	opf \|= REQ_META;
2798	if (buffer_prio(bh))
2799	opf \|= REQ_PRIO;
2800
2801	bio = bio_alloc(bh->b_bdev, 1, opf, GFP_NOIO);
2802
2803	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
2804
2805	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2806	bio->bi_write_hint = write_hint;
2807
2808	bio_add_folio_nofail(bio, bh->b_folio, bh->b_size, bh_offset(bh));
2809
2810	bio->bi_end_io = end_bio_bh_io_sync;
2811	bio->bi_private = bh;
2812
2813	/* Take care of bh's that straddle the end of the device */
2814	guard_bio_eod(bio);
2815
2816	if (wbc) {
2817	wbc_init_bio(wbc, bio);
2818	wbc_account_cgroup_owner(wbc, bh->b_folio, bh->b_size);
2819	}
2820
2821	blk_crypto_submit_bio(bio);
2822	}
2823
2824	void submit_bh(blk_opf_t opf, struct buffer_head *bh)
2825	{
2826	submit_bh_wbc(opf, bh, WRITE_LIFE_NOT_SET, NULL);
2827	}
2828	EXPORT_SYMBOL(submit_bh);
2829
2830	void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2831	{
2832	lock_buffer(bh);
2833	if (!test_clear_buffer_dirty(bh)) {
2834	unlock_buffer(bh);
2835	return;
2836	}
2837	bh->b_end_io = end_buffer_write_sync;
2838	get_bh(bh);
2839	submit_bh(REQ_OP_WRITE \| op_flags, bh);
2840	}
2841	EXPORT_SYMBOL(write_dirty_buffer);
2842
2843	/*
2844	* For a data-integrity writeout, we need to wait upon any in-progress I/O
2845	* and then start new I/O and then wait upon it. The caller must have a ref on
2846	* the buffer_head.
2847	*/
2848	int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2849	{
2850	WARN_ON(atomic_read(&bh->b_count) < 1);
2851	lock_buffer(bh);
2852	if (test_clear_buffer_dirty(bh)) {
2853	/*
2854	* The bh should be mapped, but it might not be if the
2855	* device was hot-removed. Not much we can do but fail the I/O.
2856	*/
2857	if (!buffer_mapped(bh)) {
2858	unlock_buffer(bh);
2859	return -EIO;
2860	}
2861
2862	get_bh(bh);
2863	bh->b_end_io = end_buffer_write_sync;
2864	submit_bh(REQ_OP_WRITE \| op_flags, bh);
2865	wait_on_buffer(bh);
2866	if (!buffer_uptodate(bh))
2867	return -EIO;
2868	} else {
2869	unlock_buffer(bh);
2870	}
2871	return 0;
2872	}
2873	EXPORT_SYMBOL(__sync_dirty_buffer);
2874
2875	int sync_dirty_buffer(struct buffer_head *bh)
2876	{
2877	return __sync_dirty_buffer(bh, REQ_SYNC);
2878	}
2879	EXPORT_SYMBOL(sync_dirty_buffer);
2880
2881	static inline int buffer_busy(struct buffer_head *bh)
2882	{
2883	return atomic_read(&bh->b_count) \|
2884	(bh->b_state & ((1 << BH_Dirty) \| (1 << BH_Lock)));
2885	}
2886
2887	static bool
2888	drop_buffers(struct folio folio, struct buffer_head *buffers_to_free)
2889	{
2890	struct buffer_head *head = folio_buffers(folio);
2891	struct buffer_head *bh;
2892
2893	bh = head;
2894	do {
2895	if (buffer_busy(bh))
2896	goto failed;
2897	bh = bh->b_this_page;
2898	} while (bh != head);
2899
2900	do {
2901	struct buffer_head *next = bh->b_this_page;
2902
2903	if (bh->b_assoc_map)
2904	__remove_assoc_queue(bh);
2905	bh = next;
2906	} while (bh != head);
2907	*buffers_to_free = head;
2908	folio_detach_private(folio);
2909	return true;
2910	failed:
2911	return false;
2912	}
2913
2914	/**
2915	* try_to_free_buffers - Release buffers attached to this folio.
2916	* @folio: The folio.
2917	*
2918	* If any buffers are in use (dirty, under writeback, elevated refcount),
2919	* no buffers will be freed.
2920	*
2921	* If the folio is dirty but all the buffers are clean then we need to
2922	* be sure to mark the folio clean as well. This is because the folio
2923	* may be against a block device, and a later reattachment of buffers
2924	* to a dirty folio will set all buffers dirty. Which would corrupt
2925	* filesystem data on the same device.
2926	*
2927	* The same applies to regular filesystem folios: if all the buffers are
2928	* clean then we set the folio clean and proceed. To do that, we require
2929	* total exclusion from block_dirty_folio(). That is obtained with
2930	* i_private_lock.
2931	*
2932	* Exclusion against try_to_free_buffers may be obtained by either
2933	* locking the folio or by holding its mapping's i_private_lock.
2934	*
2935	* Context: Process context. @folio must be locked. Will not sleep.
2936	* Return: true if all buffers attached to this folio were freed.
2937	*/
2938	bool try_to_free_buffers(struct folio *folio)
2939	{
2940	struct address_space * const mapping = folio->mapping;
2941	struct buffer_head *buffers_to_free = NULL;
2942	bool ret = 0;
2943
2944	BUG_ON(!folio_test_locked(folio));
2945	if (folio_test_writeback(folio))
2946	return false;
2947
2948	/* Misconfigured folio check */
2949	if (WARN_ON_ONCE(!folio_buffers(folio)))
2950	return true;
2951
2952	if (mapping == NULL) { /* can this still happen? */
2953	ret = drop_buffers(folio, &buffers_to_free);
2954	goto out;
2955	}
2956
2957	spin_lock(&mapping->i_private_lock);
2958	ret = drop_buffers(folio, &buffers_to_free);
2959
2960	/*
2961	* If the filesystem writes its buffers by hand (eg ext3)
2962	* then we can have clean buffers against a dirty folio. We
2963	* clean the folio here; otherwise the VM will never notice
2964	* that the filesystem did any IO at all.
2965	*
2966	* Also, during truncate, discard_buffer will have marked all
2967	* the folio's buffers clean. We discover that here and clean
2968	* the folio also.
2969	*
2970	* i_private_lock must be held over this entire operation in order
2971	* to synchronise against block_dirty_folio and prevent the
2972	* dirty bit from being lost.
2973	*/
2974	if (ret)
2975	folio_cancel_dirty(folio);
2976	spin_unlock(&mapping->i_private_lock);
2977	out:
2978	if (buffers_to_free) {
2979	struct buffer_head *bh = buffers_to_free;
2980
2981	do {
2982	struct buffer_head *next = bh->b_this_page;
2983	free_buffer_head(bh);
2984	bh = next;
2985	} while (bh != buffers_to_free);
2986	}
2987	return ret;
2988	}
2989	EXPORT_SYMBOL(try_to_free_buffers);
2990
2991	/*
2992	* Buffer-head allocation
2993	*/
2994	static struct kmem_cache *bh_cachep __ro_after_init;
2995
2996	/*
2997	* Once the number of bh's in the machine exceeds this level, we start
2998	* stripping them in writeback.
2999	*/
3000	static unsigned long max_buffer_heads __ro_after_init;
3001
3002	int buffer_heads_over_limit;
3003
3004	struct bh_accounting {
3005	int nr; /* Number of live bh's */
3006	int ratelimit; /* Limit cacheline bouncing */
3007	};
3008
3009	static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3010
3011	static void recalc_bh_state(void)
3012	{
3013	int i;
3014	int tot = 0;
3015
3016	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3017	return;
3018	__this_cpu_write(bh_accounting.ratelimit, 0);
3019	for_each_online_cpu(i)
3020	tot += per_cpu(bh_accounting, i).nr;
3021	buffer_heads_over_limit = (tot > max_buffer_heads);
3022	}
3023
3024	struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3025	{
3026	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3027	if (ret) {
3028	INIT_LIST_HEAD(&ret->b_assoc_buffers);
3029	spin_lock_init(&ret->b_uptodate_lock);
3030	preempt_disable();
3031	__this_cpu_inc(bh_accounting.nr);
3032	recalc_bh_state();
3033	preempt_enable();
3034	}
3035	return ret;
3036	}
3037	EXPORT_SYMBOL(alloc_buffer_head);
3038
3039	void free_buffer_head(struct buffer_head *bh)
3040	{
3041	BUG_ON(!list_empty(&bh->b_assoc_buffers));
3042	kmem_cache_free(bh_cachep, bh);
3043	preempt_disable();
3044	__this_cpu_dec(bh_accounting.nr);
3045	recalc_bh_state();
3046	preempt_enable();
3047	}
3048	EXPORT_SYMBOL(free_buffer_head);
3049
3050	static int buffer_exit_cpu_dead(unsigned int cpu)
3051	{
3052	int i;
3053	struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3054
3055	for (i = 0; i < BH_LRU_SIZE; i++) {
3056	brelse(b->bhs[i]);
3057	b->bhs[i] = NULL;
3058	}
3059	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3060	per_cpu(bh_accounting, cpu).nr = 0;
3061	return 0;
3062	}
3063
3064	/**
3065	* bh_uptodate_or_lock - Test whether the buffer is uptodate
3066	* @bh: struct buffer_head
3067	*
3068	* Return true if the buffer is up-to-date and false,
3069	* with the buffer locked, if not.
3070	*/
3071	int bh_uptodate_or_lock(struct buffer_head *bh)
3072	{
3073	if (!buffer_uptodate(bh)) {
3074	lock_buffer(bh);
3075	if (!buffer_uptodate(bh))
3076	return 0;
3077	unlock_buffer(bh);
3078	}
3079	return 1;
3080	}
3081	EXPORT_SYMBOL(bh_uptodate_or_lock);
3082
3083	/**
3084	* __bh_read - Submit read for a locked buffer
3085	* @bh: struct buffer_head
3086	* @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3087	* @wait: wait until reading finish
3088	*
3089	* Returns zero on success or don't wait, and -EIO on error.
3090	*/
3091	int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait)
3092	{
3093	int ret = 0;
3094
3095	BUG_ON(!buffer_locked(bh));
3096
3097	get_bh(bh);
3098	bh->b_end_io = end_buffer_read_sync;
3099	submit_bh(REQ_OP_READ \| op_flags, bh);
3100	if (wait) {
3101	wait_on_buffer(bh);
3102	if (!buffer_uptodate(bh))
3103	ret = -EIO;
3104	}
3105	return ret;
3106	}
3107	EXPORT_SYMBOL(__bh_read);
3108
3109	/**
3110	* __bh_read_batch - Submit read for a batch of unlocked buffers
3111	* @nr: entry number of the buffer batch
3112	* @bhs: a batch of struct buffer_head
3113	* @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3114	* @force_lock: force to get a lock on the buffer if set, otherwise drops any
3115	* buffer that cannot lock.
3116	*
3117	* Returns zero on success or don't wait, and -EIO on error.
3118	*/
3119	void __bh_read_batch(int nr, struct buffer_head *bhs[],
3120	blk_opf_t op_flags, bool force_lock)
3121	{
3122	int i;
3123
3124	for (i = 0; i < nr; i++) {
3125	struct buffer_head *bh = bhs[i];
3126
3127	if (buffer_uptodate(bh))
3128	continue;
3129
3130	if (force_lock)
3131	lock_buffer(bh);
3132	else
3133	if (!trylock_buffer(bh))
3134	continue;
3135
3136	if (buffer_uptodate(bh)) {
3137	unlock_buffer(bh);
3138	continue;
3139	}
3140
3141	bh->b_end_io = end_buffer_read_sync;
3142	get_bh(bh);
3143	submit_bh(REQ_OP_READ \| op_flags, bh);
3144	}
3145	}
3146	EXPORT_SYMBOL(__bh_read_batch);
3147
3148	void __init buffer_init(void)
3149	{
3150	unsigned long nrpages;
3151	int ret;
3152
3153	bh_cachep = KMEM_CACHE(buffer_head,
3154	SLAB_RECLAIM_ACCOUNT\|SLAB_PANIC);
3155	/*
3156	* Limit the bh occupancy to 10% of ZONE_NORMAL
3157	*/
3158	nrpages = (nr_free_buffer_pages() * 10) / 100;
3159	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3160	ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3161	NULL, buffer_exit_cpu_dead);
3162	WARN_ON(ret < 0);
3163	}