linux - fs/buffer.c

3401 lines · 88.1 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/file.h>
33	#include <linux/quotaops.h>
34	#include <linux/highmem.h>
35	#include <linux/export.h>
36	#include <linux/backing-dev.h>
37	#include <linux/writeback.h>
38	#include <linux/hash.h>
39	#include <linux/suspend.h>
40	#include <linux/buffer_head.h>
41	#include <linux/task_io_accounting_ops.h>
42	#include <linux/bio.h>
43	#include <linux/cpu.h>
44	#include <linux/bitops.h>
45	#include <linux/mpage.h>
46	#include <linux/bit_spinlock.h>
47	#include <linux/pagevec.h>
48	#include <linux/sched/mm.h>
49	#include <trace/events/block.h>
50	#include <linux/fscrypt.h>
51
52	#include "internal.h"
53
54	static int fsync_buffers_list(spinlock_t lock, struct list_head list);
55	static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
56	struct writeback_control *wbc);
57
58	#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
59
60	inline void touch_buffer(struct buffer_head *bh)
61	{
62	trace_block_touch_buffer(bh);
63	mark_page_accessed(bh->b_page);
64	}
65	EXPORT_SYMBOL(touch_buffer);
66
67	void __lock_buffer(struct buffer_head *bh)
68	{
69	wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
70	}
71	EXPORT_SYMBOL(__lock_buffer);
72
73	void unlock_buffer(struct buffer_head *bh)
74	{
75	clear_bit_unlock(BH_Lock, &bh->b_state);
76	smp_mb__after_atomic();
77	wake_up_bit(&bh->b_state, BH_Lock);
78	}
79	EXPORT_SYMBOL(unlock_buffer);
80
81	/*
82	* Returns if the page has dirty or writeback buffers. If all the buffers
83	* are unlocked and clean then the PageDirty information is stale. If
84	* any of the pages are locked, it is assumed they are locked for IO.
85	*/
86	void buffer_check_dirty_writeback(struct page *page,
87	bool dirty, bool writeback)
88	{
89	struct buffer_head head, bh;
90	*dirty = false;
91	*writeback = false;
92
93	BUG_ON(!PageLocked(page));
94
95	if (!page_has_buffers(page))
96	return;
97
98	if (PageWriteback(page))
99	*writeback = true;
100
101	head = page_buffers(page);
102	bh = head;
103	do {
104	if (buffer_locked(bh))
105	*writeback = true;
106
107	if (buffer_dirty(bh))
108	*dirty = true;
109
110	bh = bh->b_this_page;
111	} while (bh != head);
112	}
113	EXPORT_SYMBOL(buffer_check_dirty_writeback);
114
115	/*
116	* Block until a buffer comes unlocked. This doesn't stop it
117	* from becoming locked again - you have to lock it yourself
118	* if you want to preserve its state.
119	*/
120	void __wait_on_buffer(struct buffer_head * bh)
121	{
122	wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
123	}
124	EXPORT_SYMBOL(__wait_on_buffer);
125
126	static void buffer_io_error(struct buffer_head bh, char msg)
127	{
128	if (!test_bit(BH_Quiet, &bh->b_state))
129	printk_ratelimited(KERN_ERR
130	"Buffer I/O error on dev %pg, logical block %llu%s\n",
131	bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
132	}
133
134	/*
135	* End-of-IO handler helper function which does not touch the bh after
136	* unlocking it.
137	* Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
138	* a race there is benign: unlock_buffer() only use the bh's address for
139	* hashing after unlocking the buffer, so it doesn't actually touch the bh
140	* itself.
141	*/
142	static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
143	{
144	if (uptodate) {
145	set_buffer_uptodate(bh);
146	} else {
147	/* This happens, due to failed read-ahead attempts. */
148	clear_buffer_uptodate(bh);
149	}
150	unlock_buffer(bh);
151	}
152
153	/*
154	* Default synchronous end-of-IO handler.. Just mark it up-to-date and
155	* unlock the buffer. This is what ll_rw_block uses too.
156	*/
157	void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
158	{
159	__end_buffer_read_notouch(bh, uptodate);
160	put_bh(bh);
161	}
162	EXPORT_SYMBOL(end_buffer_read_sync);
163
164	void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
165	{
166	if (uptodate) {
167	set_buffer_uptodate(bh);
168	} else {
169	buffer_io_error(bh, ", lost sync page write");
170	mark_buffer_write_io_error(bh);
171	clear_buffer_uptodate(bh);
172	}
173	unlock_buffer(bh);
174	put_bh(bh);
175	}
176	EXPORT_SYMBOL(end_buffer_write_sync);
177
178	/*
179	* Various filesystems appear to want __find_get_block to be non-blocking.
180	* But it's the page lock which protects the buffers. To get around this,
181	* we get exclusion from try_to_free_buffers with the blockdev mapping's
182	* private_lock.
183	*
184	* Hack idea: for the blockdev mapping, private_lock contention
185	* may be quite high. This code could TryLock the page, and if that
186	* succeeds, there is no need to take private_lock.
187	*/
188	static struct buffer_head *
189	__find_get_block_slow(struct block_device *bdev, sector_t block)
190	{
191	struct inode *bd_inode = bdev->bd_inode;
192	struct address_space *bd_mapping = bd_inode->i_mapping;
193	struct buffer_head *ret = NULL;
194	pgoff_t index;
195	struct buffer_head *bh;
196	struct buffer_head *head;
197	struct page *page;
198	int all_mapped = 1;
199	static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
200
201	index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
202	page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
203	if (!page)
204	goto out;
205
206	spin_lock(&bd_mapping->private_lock);
207	if (!page_has_buffers(page))
208	goto out_unlock;
209	head = page_buffers(page);
210	bh = head;
211	do {
212	if (!buffer_mapped(bh))
213	all_mapped = 0;
214	else if (bh->b_blocknr == block) {
215	ret = bh;
216	get_bh(bh);
217	goto out_unlock;
218	}
219	bh = bh->b_this_page;
220	} while (bh != head);
221
222	/* we might be here because some of the buffers on this page are
223	* not mapped. This is due to various races between
224	* file io on the block device and getblk. It gets dealt with
225	* elsewhere, don't buffer_error if we had some unmapped buffers
226	*/
227	ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
228	if (all_mapped && __ratelimit(&last_warned)) {
229	printk("__find_get_block_slow() failed. block=%llu, "
230	"b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
231	"device %pg blocksize: %d\n",
232	(unsigned long long)block,
233	(unsigned long long)bh->b_blocknr,
234	bh->b_state, bh->b_size, bdev,
235	1 << bd_inode->i_blkbits);
236	}
237	out_unlock:
238	spin_unlock(&bd_mapping->private_lock);
239	put_page(page);
240	out:
241	return ret;
242	}
243
244	static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
245	{
246	unsigned long flags;
247	struct buffer_head *first;
248	struct buffer_head *tmp;
249	struct page *page;
250	int page_uptodate = 1;
251
252	BUG_ON(!buffer_async_read(bh));
253
254	page = bh->b_page;
255	if (uptodate) {
256	set_buffer_uptodate(bh);
257	} else {
258	clear_buffer_uptodate(bh);
259	buffer_io_error(bh, ", async page read");
260	SetPageError(page);
261	}
262
263	/*
264	* Be _very_ careful from here on. Bad things can happen if
265	* two buffer heads end IO at almost the same time and both
266	* decide that the page is now completely done.
267	*/
268	first = page_buffers(page);
269	spin_lock_irqsave(&first->b_uptodate_lock, flags);
270	clear_buffer_async_read(bh);
271	unlock_buffer(bh);
272	tmp = bh;
273	do {
274	if (!buffer_uptodate(tmp))
275	page_uptodate = 0;
276	if (buffer_async_read(tmp)) {
277	BUG_ON(!buffer_locked(tmp));
278	goto still_busy;
279	}
280	tmp = tmp->b_this_page;
281	} while (tmp != bh);
282	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
283
284	/*
285	* If none of the buffers had errors and they are all
286	* uptodate then we can set the page uptodate.
287	*/
288	if (page_uptodate && !PageError(page))
289	SetPageUptodate(page);
290	unlock_page(page);
291	return;
292
293	still_busy:
294	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
295	return;
296	}
297
298	struct decrypt_bh_ctx {
299	struct work_struct work;
300	struct buffer_head *bh;
301	};
302
303	static void decrypt_bh(struct work_struct *work)
304	{
305	struct decrypt_bh_ctx *ctx =
306	container_of(work, struct decrypt_bh_ctx, work);
307	struct buffer_head *bh = ctx->bh;
308	int err;
309
310	err = fscrypt_decrypt_pagecache_blocks(bh->b_page, bh->b_size,
311	bh_offset(bh));
312	end_buffer_async_read(bh, err == 0);
313	kfree(ctx);
314	}
315
316	/*
317	* I/O completion handler for block_read_full_page() - pages
318	* which come unlocked at the end of I/O.
319	*/
320	static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
321	{
322	/* Decrypt if needed */
323	if (uptodate &&
324	fscrypt_inode_uses_fs_layer_crypto(bh->b_page->mapping->host)) {
325	struct decrypt_bh_ctx ctx = kmalloc(sizeof(ctx), GFP_ATOMIC);
326
327	if (ctx) {
328	INIT_WORK(&ctx->work, decrypt_bh);
329	ctx->bh = bh;
330	fscrypt_enqueue_decrypt_work(&ctx->work);
331	return;
332	}
333	uptodate = 0;
334	}
335	end_buffer_async_read(bh, uptodate);
336	}
337
338	/*
339	* Completion handler for block_write_full_page() - pages which are unlocked
340	* during I/O, and which have PageWriteback cleared upon I/O completion.
341	*/
342	void end_buffer_async_write(struct buffer_head *bh, int uptodate)
343	{
344	unsigned long flags;
345	struct buffer_head *first;
346	struct buffer_head *tmp;
347	struct page *page;
348
349	BUG_ON(!buffer_async_write(bh));
350
351	page = bh->b_page;
352	if (uptodate) {
353	set_buffer_uptodate(bh);
354	} else {
355	buffer_io_error(bh, ", lost async page write");
356	mark_buffer_write_io_error(bh);
357	clear_buffer_uptodate(bh);
358	SetPageError(page);
359	}
360
361	first = page_buffers(page);
362	spin_lock_irqsave(&first->b_uptodate_lock, flags);
363
364	clear_buffer_async_write(bh);
365	unlock_buffer(bh);
366	tmp = bh->b_this_page;
367	while (tmp != bh) {
368	if (buffer_async_write(tmp)) {
369	BUG_ON(!buffer_locked(tmp));
370	goto still_busy;
371	}
372	tmp = tmp->b_this_page;
373	}
374	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
375	end_page_writeback(page);
376	return;
377
378	still_busy:
379	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
380	return;
381	}
382	EXPORT_SYMBOL(end_buffer_async_write);
383
384	/*
385	* If a page's buffers are under async readin (end_buffer_async_read
386	* completion) then there is a possibility that another thread of
387	* control could lock one of the buffers after it has completed
388	* but while some of the other buffers have not completed. This
389	* locked buffer would confuse end_buffer_async_read() into not unlocking
390	* the page. So the absence of BH_Async_Read tells end_buffer_async_read()
391	* that this buffer is not under async I/O.
392	*
393	* The page comes unlocked when it has no locked buffer_async buffers
394	* left.
395	*
396	* PageLocked prevents anyone starting new async I/O reads any of
397	* the buffers.
398	*
399	* PageWriteback is used to prevent simultaneous writeout of the same
400	* page.
401	*
402	* PageLocked prevents anyone from starting writeback of a page which is
403	* under read I/O (PageWriteback is only ever set against a locked page).
404	*/
405	static void mark_buffer_async_read(struct buffer_head *bh)
406	{
407	bh->b_end_io = end_buffer_async_read_io;
408	set_buffer_async_read(bh);
409	}
410
411	static void mark_buffer_async_write_endio(struct buffer_head *bh,
412	bh_end_io_t *handler)
413	{
414	bh->b_end_io = handler;
415	set_buffer_async_write(bh);
416	}
417
418	void mark_buffer_async_write(struct buffer_head *bh)
419	{
420	mark_buffer_async_write_endio(bh, end_buffer_async_write);
421	}
422	EXPORT_SYMBOL(mark_buffer_async_write);
423
424
425	/*
426	* fs/buffer.c contains helper functions for buffer-backed address space's
427	* fsync functions. A common requirement for buffer-based filesystems is
428	* that certain data from the backing blockdev needs to be written out for
429	* a successful fsync(). For example, ext2 indirect blocks need to be
430	* written back and waited upon before fsync() returns.
431	*
432	* The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
433	* inode_has_buffers() and invalidate_inode_buffers() are provided for the
434	* management of a list of dependent buffers at ->i_mapping->private_list.
435	*
436	* Locking is a little subtle: try_to_free_buffers() will remove buffers
437	* from their controlling inode's queue when they are being freed. But
438	* try_to_free_buffers() will be operating against the blockdev mapping
439	* at the time, not against the S_ISREG file which depends on those buffers.
440	* So the locking for private_list is via the private_lock in the address_space
441	* which backs the buffers. Which is different from the address_space
442	* against which the buffers are listed. So for a particular address_space,
443	* mapping->private_lock does not protect mapping->private_list! In fact,
444	* mapping->private_list will always be protected by the backing blockdev's
445	* ->private_lock.
446	*
447	* Which introduces a requirement: all buffers on an address_space's
448	* ->private_list must be from the same address_space: the blockdev's.
449	*
450	* address_spaces which do not place buffers at ->private_list via these
451	* utility functions are free to use private_lock and private_list for
452	* whatever they want. The only requirement is that list_empty(private_list)
453	* be true at clear_inode() time.
454	*
455	* FIXME: clear_inode should not call invalidate_inode_buffers(). The
456	* filesystems should do that. invalidate_inode_buffers() should just go
457	* BUG_ON(!list_empty).
458	*
459	* FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
460	* take an address_space, not an inode. And it should be called
461	* mark_buffer_dirty_fsync() to clearly define why those buffers are being
462	* queued up.
463	*
464	* FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
465	* list if it is already on a list. Because if the buffer is on a list,
466	* it must already be on the right one. If not, the filesystem is being
467	* silly. This will save a ton of locking. But first we have to ensure
468	* that buffers are taken off the old inode's list when they are freed
469	* (presumably in truncate). That requires careful auditing of all
470	* filesystems (do it inside bforget()). It could also be done by bringing
471	* b_inode back.
472	*/
473
474	/*
475	* The buffer's backing address_space's private_lock must be held
476	*/
477	static void __remove_assoc_queue(struct buffer_head *bh)
478	{
479	list_del_init(&bh->b_assoc_buffers);
480	WARN_ON(!bh->b_assoc_map);
481	bh->b_assoc_map = NULL;
482	}
483
484	int inode_has_buffers(struct inode *inode)
485	{
486	return !list_empty(&inode->i_data.private_list);
487	}
488
489	/*
490	* osync is designed to support O_SYNC io. It waits synchronously for
491	* all already-submitted IO to complete, but does not queue any new
492	* writes to the disk.
493	*
494	* To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
495	* you dirty the buffers, and then use osync_inode_buffers to wait for
496	* completion. Any other dirty buffers which are not yet queued for
497	* write will not be flushed to disk by the osync.
498	*/
499	static int osync_buffers_list(spinlock_t lock, struct list_head list)
500	{
501	struct buffer_head *bh;
502	struct list_head *p;
503	int err = 0;
504
505	spin_lock(lock);
506	repeat:
507	list_for_each_prev(p, list) {
508	bh = BH_ENTRY(p);
509	if (buffer_locked(bh)) {
510	get_bh(bh);
511	spin_unlock(lock);
512	wait_on_buffer(bh);
513	if (!buffer_uptodate(bh))
514	err = -EIO;
515	brelse(bh);
516	spin_lock(lock);
517	goto repeat;
518	}
519	}
520	spin_unlock(lock);
521	return err;
522	}
523
524	void emergency_thaw_bdev(struct super_block *sb)
525	{
526	while (sb->s_bdev && !thaw_bdev(sb->s_bdev))
527	printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
528	}
529
530	/**
531	* sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
532	* @mapping: the mapping which wants those buffers written
533	*
534	* Starts I/O against the buffers at mapping->private_list, and waits upon
535	* that I/O.
536	*
537	* Basically, this is a convenience function for fsync().
538	* @mapping is a file or directory which needs those buffers to be written for
539	* a successful fsync().
540	*/
541	int sync_mapping_buffers(struct address_space *mapping)
542	{
543	struct address_space *buffer_mapping = mapping->private_data;
544
545	if (buffer_mapping == NULL \|\| list_empty(&mapping->private_list))
546	return 0;
547
548	return fsync_buffers_list(&buffer_mapping->private_lock,
549	&mapping->private_list);
550	}
551	EXPORT_SYMBOL(sync_mapping_buffers);
552
553	/*
554	* Called when we've recently written block `bblock', and it is known that
555	* `bblock' was for a buffer_boundary() buffer. This means that the block at
556	* `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
557	* dirty, schedule it for IO. So that indirects merge nicely with their data.
558	*/
559	void write_boundary_block(struct block_device *bdev,
560	sector_t bblock, unsigned blocksize)
561	{
562	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
563	if (bh) {
564	if (buffer_dirty(bh))
565	ll_rw_block(REQ_OP_WRITE, 0, 1, &bh);
566	put_bh(bh);
567	}
568	}
569
570	void mark_buffer_dirty_inode(struct buffer_head bh, struct inode inode)
571	{
572	struct address_space *mapping = inode->i_mapping;
573	struct address_space *buffer_mapping = bh->b_page->mapping;
574
575	mark_buffer_dirty(bh);
576	if (!mapping->private_data) {
577	mapping->private_data = buffer_mapping;
578	} else {
579	BUG_ON(mapping->private_data != buffer_mapping);
580	}
581	if (!bh->b_assoc_map) {
582	spin_lock(&buffer_mapping->private_lock);
583	list_move_tail(&bh->b_assoc_buffers,
584	&mapping->private_list);
585	bh->b_assoc_map = mapping;
586	spin_unlock(&buffer_mapping->private_lock);
587	}
588	}
589	EXPORT_SYMBOL(mark_buffer_dirty_inode);
590
591	/*
592	* Add a page to the dirty page list.
593	*
594	* It is a sad fact of life that this function is called from several places
595	* deeply under spinlocking. It may not sleep.
596	*
597	* If the page has buffers, the uptodate buffers are set dirty, to preserve
598	* dirty-state coherency between the page and the buffers. It the page does
599	* not have buffers then when they are later attached they will all be set
600	* dirty.
601	*
602	* The buffers are dirtied before the page is dirtied. There's a small race
603	* window in which a writepage caller may see the page cleanness but not the
604	* buffer dirtiness. That's fine. If this code were to set the page dirty
605	* before the buffers, a concurrent writepage caller could clear the page dirty
606	* bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
607	* page on the dirty page list.
608	*
609	* We use private_lock to lock against try_to_free_buffers while using the
610	* page's buffer list. Also use this to protect against clean buffers being
611	* added to the page after it was set dirty.
612	*
613	* FIXME: may need to call ->reservepage here as well. That's rather up to the
614	* address_space though.
615	*/
616	bool block_dirty_folio(struct address_space mapping, struct folio folio)
617	{
618	struct buffer_head *head;
619	bool newly_dirty;
620
621	spin_lock(&mapping->private_lock);
622	head = folio_buffers(folio);
623	if (head) {
624	struct buffer_head *bh = head;
625
626	do {
627	set_buffer_dirty(bh);
628	bh = bh->b_this_page;
629	} while (bh != head);
630	}
631	/*
632	* Lock out page's memcg migration to keep PageDirty
633	* synchronized with per-memcg dirty page counters.
634	*/
635	folio_memcg_lock(folio);
636	newly_dirty = !folio_test_set_dirty(folio);
637	spin_unlock(&mapping->private_lock);
638
639	if (newly_dirty)
640	__folio_mark_dirty(folio, mapping, 1);
641
642	folio_memcg_unlock(folio);
643
644	if (newly_dirty)
645	__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
646
647	return newly_dirty;
648	}
649	EXPORT_SYMBOL(block_dirty_folio);
650
651	/*
652	* Write out and wait upon a list of buffers.
653	*
654	* We have conflicting pressures: we want to make sure that all
655	* initially dirty buffers get waited on, but that any subsequently
656	* dirtied buffers don't. After all, we don't want fsync to last
657	* forever if somebody is actively writing to the file.
658	*
659	* Do this in two main stages: first we copy dirty buffers to a
660	* temporary inode list, queueing the writes as we go. Then we clean
661	* up, waiting for those writes to complete.
662	*
663	* During this second stage, any subsequent updates to the file may end
664	* up refiling the buffer on the original inode's dirty list again, so
665	* there is a chance we will end up with a buffer queued for write but
666	* not yet completed on that list. So, as a final cleanup we go through
667	* the osync code to catch these locked, dirty buffers without requeuing
668	* any newly dirty buffers for write.
669	*/
670	static int fsync_buffers_list(spinlock_t lock, struct list_head list)
671	{
672	struct buffer_head *bh;
673	struct list_head tmp;
674	struct address_space *mapping;
675	int err = 0, err2;
676	struct blk_plug plug;
677
678	INIT_LIST_HEAD(&tmp);
679	blk_start_plug(&plug);
680
681	spin_lock(lock);
682	while (!list_empty(list)) {
683	bh = BH_ENTRY(list->next);
684	mapping = bh->b_assoc_map;
685	__remove_assoc_queue(bh);
686	/* Avoid race with mark_buffer_dirty_inode() which does
687	* a lockless check and we rely on seeing the dirty bit */
688	smp_mb();
689	if (buffer_dirty(bh) \|\| buffer_locked(bh)) {
690	list_add(&bh->b_assoc_buffers, &tmp);
691	bh->b_assoc_map = mapping;
692	if (buffer_dirty(bh)) {
693	get_bh(bh);
694	spin_unlock(lock);
695	/*
696	* Ensure any pending I/O completes so that
697	* write_dirty_buffer() actually writes the
698	* current contents - it is a noop if I/O is
699	* still in flight on potentially older
700	* contents.
701	*/
702	write_dirty_buffer(bh, REQ_SYNC);
703
704	/*
705	* Kick off IO for the previous mapping. Note
706	* that we will not run the very last mapping,
707	* wait_on_buffer() will do that for us
708	* through sync_buffer().
709	*/
710	brelse(bh);
711	spin_lock(lock);
712	}
713	}
714	}
715
716	spin_unlock(lock);
717	blk_finish_plug(&plug);
718	spin_lock(lock);
719
720	while (!list_empty(&tmp)) {
721	bh = BH_ENTRY(tmp.prev);
722	get_bh(bh);
723	mapping = bh->b_assoc_map;
724	__remove_assoc_queue(bh);
725	/* Avoid race with mark_buffer_dirty_inode() which does
726	* a lockless check and we rely on seeing the dirty bit */
727	smp_mb();
728	if (buffer_dirty(bh)) {
729	list_add(&bh->b_assoc_buffers,
730	&mapping->private_list);
731	bh->b_assoc_map = mapping;
732	}
733	spin_unlock(lock);
734	wait_on_buffer(bh);
735	if (!buffer_uptodate(bh))
736	err = -EIO;
737	brelse(bh);
738	spin_lock(lock);
739	}
740
741	spin_unlock(lock);
742	err2 = osync_buffers_list(lock, list);
743	if (err)
744	return err;
745	else
746	return err2;
747	}
748
749	/*
750	* Invalidate any and all dirty buffers on a given inode. We are
751	* probably unmounting the fs, but that doesn't mean we have already
752	* done a sync(). Just drop the buffers from the inode list.
753	*
754	* NOTE: we take the inode's blockdev's mapping's private_lock. Which
755	* assumes that all the buffers are against the blockdev. Not true
756	* for reiserfs.
757	*/
758	void invalidate_inode_buffers(struct inode *inode)
759	{
760	if (inode_has_buffers(inode)) {
761	struct address_space *mapping = &inode->i_data;
762	struct list_head *list = &mapping->private_list;
763	struct address_space *buffer_mapping = mapping->private_data;
764
765	spin_lock(&buffer_mapping->private_lock);
766	while (!list_empty(list))
767	__remove_assoc_queue(BH_ENTRY(list->next));
768	spin_unlock(&buffer_mapping->private_lock);
769	}
770	}
771	EXPORT_SYMBOL(invalidate_inode_buffers);
772
773	/*
774	* Remove any clean buffers from the inode's buffer list. This is called
775	* when we're trying to free the inode itself. Those buffers can pin it.
776	*
777	* Returns true if all buffers were removed.
778	*/
779	int remove_inode_buffers(struct inode *inode)
780	{
781	int ret = 1;
782
783	if (inode_has_buffers(inode)) {
784	struct address_space *mapping = &inode->i_data;
785	struct list_head *list = &mapping->private_list;
786	struct address_space *buffer_mapping = mapping->private_data;
787
788	spin_lock(&buffer_mapping->private_lock);
789	while (!list_empty(list)) {
790	struct buffer_head *bh = BH_ENTRY(list->next);
791	if (buffer_dirty(bh)) {
792	ret = 0;
793	break;
794	}
795	__remove_assoc_queue(bh);
796	}
797	spin_unlock(&buffer_mapping->private_lock);
798	}
799	return ret;
800	}
801
802	/*
803	* Create the appropriate buffers when given a page for data area and
804	* the size of each buffer.. Use the bh->b_this_page linked list to
805	* follow the buffers created. Return NULL if unable to create more
806	* buffers.
807	*
808	* The retry flag is used to differentiate async IO (paging, swapping)
809	* which may not fail from ordinary buffer allocations.
810	*/
811	struct buffer_head alloc_page_buffers(struct page page, unsigned long size,
812	bool retry)
813	{
814	struct buffer_head bh, head;
815	gfp_t gfp = GFP_NOFS \| __GFP_ACCOUNT;
816	long offset;
817	struct mem_cgroup memcg, old_memcg;
818
819	if (retry)
820	gfp \|= __GFP_NOFAIL;
821
822	/* The page lock pins the memcg */
823	memcg = page_memcg(page);
824	old_memcg = set_active_memcg(memcg);
825
826	head = NULL;
827	offset = PAGE_SIZE;
828	while ((offset -= size) >= 0) {
829	bh = alloc_buffer_head(gfp);
830	if (!bh)
831	goto no_grow;
832
833	bh->b_this_page = head;
834	bh->b_blocknr = -1;
835	head = bh;
836
837	bh->b_size = size;
838
839	/* Link the buffer to its page */
840	set_bh_page(bh, page, offset);
841	}
842	out:
843	set_active_memcg(old_memcg);
844	return head;
845	/*
846	* In case anything failed, we just free everything we got.
847	*/
848	no_grow:
849	if (head) {
850	do {
851	bh = head;
852	head = head->b_this_page;
853	free_buffer_head(bh);
854	} while (head);
855	}
856
857	goto out;
858	}
859	EXPORT_SYMBOL_GPL(alloc_page_buffers);
860
861	static inline void
862	link_dev_buffers(struct page page, struct buffer_head head)
863	{
864	struct buffer_head bh, tail;
865
866	bh = head;
867	do {
868	tail = bh;
869	bh = bh->b_this_page;
870	} while (bh);
871	tail->b_this_page = head;
872	attach_page_private(page, head);
873	}
874
875	static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
876	{
877	sector_t retval = ~((sector_t)0);
878	loff_t sz = bdev_nr_bytes(bdev);
879
880	if (sz) {
881	unsigned int sizebits = blksize_bits(size);
882	retval = (sz >> sizebits);
883	}
884	return retval;
885	}
886
887	/*
888	* Initialise the state of a blockdev page's buffers.
889	*/
890	static sector_t
891	init_page_buffers(struct page page, struct block_device bdev,
892	sector_t block, int size)
893	{
894	struct buffer_head *head = page_buffers(page);
895	struct buffer_head *bh = head;
896	int uptodate = PageUptodate(page);
897	sector_t end_block = blkdev_max_block(bdev, size);
898
899	do {
900	if (!buffer_mapped(bh)) {
901	bh->b_end_io = NULL;
902	bh->b_private = NULL;
903	bh->b_bdev = bdev;
904	bh->b_blocknr = block;
905	if (uptodate)
906	set_buffer_uptodate(bh);
907	if (block < end_block)
908	set_buffer_mapped(bh);
909	}
910	block++;
911	bh = bh->b_this_page;
912	} while (bh != head);
913
914	/*
915	* Caller needs to validate requested block against end of device.
916	*/
917	return end_block;
918	}
919
920	/*
921	* Create the page-cache page that contains the requested block.
922	*
923	* This is used purely for blockdev mappings.
924	*/
925	static int
926	grow_dev_page(struct block_device *bdev, sector_t block,
927	pgoff_t index, int size, int sizebits, gfp_t gfp)
928	{
929	struct inode *inode = bdev->bd_inode;
930	struct page *page;
931	struct buffer_head *bh;
932	sector_t end_block;
933	int ret = 0;
934	gfp_t gfp_mask;
935
936	gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) \| gfp;
937
938	/*
939	* XXX: __getblk_slow() can not really deal with failure and
940	* will endlessly loop on improvised global reclaim. Prefer
941	* looping in the allocator rather than here, at least that
942	* code knows what it's doing.
943	*/
944	gfp_mask \|= __GFP_NOFAIL;
945
946	page = find_or_create_page(inode->i_mapping, index, gfp_mask);
947
948	BUG_ON(!PageLocked(page));
949
950	if (page_has_buffers(page)) {
951	bh = page_buffers(page);
952	if (bh->b_size == size) {
953	end_block = init_page_buffers(page, bdev,
954	(sector_t)index << sizebits,
955	size);
956	goto done;
957	}
958	if (!try_to_free_buffers(page))
959	goto failed;
960	}
961
962	/*
963	* Allocate some buffers for this page
964	*/
965	bh = alloc_page_buffers(page, size, true);
966
967	/*
968	* Link the page to the buffers and initialise them. Take the
969	* lock to be atomic wrt __find_get_block(), which does not
970	* run under the page lock.
971	*/
972	spin_lock(&inode->i_mapping->private_lock);
973	link_dev_buffers(page, bh);
974	end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
975	size);
976	spin_unlock(&inode->i_mapping->private_lock);
977	done:
978	ret = (block < end_block) ? 1 : -ENXIO;
979	failed:
980	unlock_page(page);
981	put_page(page);
982	return ret;
983	}
984
985	/*
986	* Create buffers for the specified block device block's page. If
987	* that page was dirty, the buffers are set dirty also.
988	*/
989	static int
990	grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
991	{
992	pgoff_t index;
993	int sizebits;
994
995	sizebits = PAGE_SHIFT - __ffs(size);
996	index = block >> sizebits;
997
998	/*
999	* Check for a block which wants to lie outside our maximum possible
1000	* pagecache index. (this comparison is done using sector_t types).
1001	*/
1002	if (unlikely(index != block >> sizebits)) {
1003	printk(KERN_ERR "%s: requested out-of-range block %llu for "
1004	"device %pg\n",
1005	__func__, (unsigned long long)block,
1006	bdev);
1007	return -EIO;
1008	}
1009
1010	/* Create a page with the proper size buffers.. */
1011	return grow_dev_page(bdev, block, index, size, sizebits, gfp);
1012	}
1013
1014	static struct buffer_head *
1015	__getblk_slow(struct block_device *bdev, sector_t block,
1016	unsigned size, gfp_t gfp)
1017	{
1018	/* Size must be multiple of hard sectorsize */
1019	if (unlikely(size & (bdev_logical_block_size(bdev)-1) \|\|
1020	(size < 512 \|\| size > PAGE_SIZE))) {
1021	printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1022	size);
1023	printk(KERN_ERR "logical block size: %d\n",
1024	bdev_logical_block_size(bdev));
1025
1026	dump_stack();
1027	return NULL;
1028	}
1029
1030	for (;;) {
1031	struct buffer_head *bh;
1032	int ret;
1033
1034	bh = __find_get_block(bdev, block, size);
1035	if (bh)
1036	return bh;
1037
1038	ret = grow_buffers(bdev, block, size, gfp);
1039	if (ret < 0)
1040	return NULL;
1041	}
1042	}
1043
1044	/*
1045	* The relationship between dirty buffers and dirty pages:
1046	*
1047	* Whenever a page has any dirty buffers, the page's dirty bit is set, and
1048	* the page is tagged dirty in the page cache.
1049	*
1050	* At all times, the dirtiness of the buffers represents the dirtiness of
1051	* subsections of the page. If the page has buffers, the page dirty bit is
1052	* merely a hint about the true dirty state.
1053	*
1054	* When a page is set dirty in its entirety, all its buffers are marked dirty
1055	* (if the page has buffers).
1056	*
1057	* When a buffer is marked dirty, its page is dirtied, but the page's other
1058	* buffers are not.
1059	*
1060	* Also. When blockdev buffers are explicitly read with bread(), they
1061	* individually become uptodate. But their backing page remains not
1062	* uptodate - even if all of its buffers are uptodate. A subsequent
1063	* block_read_full_page() against that page will discover all the uptodate
1064	* buffers, will set the page uptodate and will perform no I/O.
1065	*/
1066
1067	/**
1068	* mark_buffer_dirty - mark a buffer_head as needing writeout
1069	* @bh: the buffer_head to mark dirty
1070	*
1071	* mark_buffer_dirty() will set the dirty bit against the buffer, then set
1072	* its backing page dirty, then tag the page as dirty in the page cache
1073	* and then attach the address_space's inode to its superblock's dirty
1074	* inode list.
1075	*
1076	* mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1077	* i_pages lock and mapping->host->i_lock.
1078	*/
1079	void mark_buffer_dirty(struct buffer_head *bh)
1080	{
1081	WARN_ON_ONCE(!buffer_uptodate(bh));
1082
1083	trace_block_dirty_buffer(bh);
1084
1085	/*
1086	* Very carefully optimize the it-is-already-dirty case.
1087	*
1088	* Don't let the final "is it dirty" escape to before we
1089	* perhaps modified the buffer.
1090	*/
1091	if (buffer_dirty(bh)) {
1092	smp_mb();
1093	if (buffer_dirty(bh))
1094	return;
1095	}
1096
1097	if (!test_set_buffer_dirty(bh)) {
1098	struct page *page = bh->b_page;
1099	struct address_space *mapping = NULL;
1100
1101	lock_page_memcg(page);
1102	if (!TestSetPageDirty(page)) {
1103	mapping = page_mapping(page);
1104	if (mapping)
1105	__set_page_dirty(page, mapping, 0);
1106	}
1107	unlock_page_memcg(page);
1108	if (mapping)
1109	__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1110	}
1111	}
1112	EXPORT_SYMBOL(mark_buffer_dirty);
1113
1114	void mark_buffer_write_io_error(struct buffer_head *bh)
1115	{
1116	struct super_block *sb;
1117
1118	set_buffer_write_io_error(bh);
1119	/* FIXME: do we need to set this in both places? */
1120	if (bh->b_page && bh->b_page->mapping)
1121	mapping_set_error(bh->b_page->mapping, -EIO);
1122	if (bh->b_assoc_map)
1123	mapping_set_error(bh->b_assoc_map, -EIO);
1124	rcu_read_lock();
1125	sb = READ_ONCE(bh->b_bdev->bd_super);
1126	if (sb)
1127	errseq_set(&sb->s_wb_err, -EIO);
1128	rcu_read_unlock();
1129	}
1130	EXPORT_SYMBOL(mark_buffer_write_io_error);
1131
1132	/*
1133	* Decrement a buffer_head's reference count. If all buffers against a page
1134	* have zero reference count, are clean and unlocked, and if the page is clean
1135	* and unlocked then try_to_free_buffers() may strip the buffers from the page
1136	* in preparation for freeing it (sometimes, rarely, buffers are removed from
1137	* a page but it ends up not being freed, and buffers may later be reattached).
1138	*/
1139	void __brelse(struct buffer_head * buf)
1140	{
1141	if (atomic_read(&buf->b_count)) {
1142	put_bh(buf);
1143	return;
1144	}
1145	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1146	}
1147	EXPORT_SYMBOL(__brelse);
1148
1149	/*
1150	* bforget() is like brelse(), except it discards any
1151	* potentially dirty data.
1152	*/
1153	void __bforget(struct buffer_head *bh)
1154	{
1155	clear_buffer_dirty(bh);
1156	if (bh->b_assoc_map) {
1157	struct address_space *buffer_mapping = bh->b_page->mapping;
1158
1159	spin_lock(&buffer_mapping->private_lock);
1160	list_del_init(&bh->b_assoc_buffers);
1161	bh->b_assoc_map = NULL;
1162	spin_unlock(&buffer_mapping->private_lock);
1163	}
1164	__brelse(bh);
1165	}
1166	EXPORT_SYMBOL(__bforget);
1167
1168	static struct buffer_head __bread_slow(struct buffer_head bh)
1169	{
1170	lock_buffer(bh);
1171	if (buffer_uptodate(bh)) {
1172	unlock_buffer(bh);
1173	return bh;
1174	} else {
1175	get_bh(bh);
1176	bh->b_end_io = end_buffer_read_sync;
1177	submit_bh(REQ_OP_READ, 0, bh);
1178	wait_on_buffer(bh);
1179	if (buffer_uptodate(bh))
1180	return bh;
1181	}
1182	brelse(bh);
1183	return NULL;
1184	}
1185
1186	/*
1187	* Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1188	* The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1189	* refcount elevated by one when they're in an LRU. A buffer can only appear
1190	* once in a particular CPU's LRU. A single buffer can be present in multiple
1191	* CPU's LRUs at the same time.
1192	*
1193	* This is a transparent caching front-end to sb_bread(), sb_getblk() and
1194	* sb_find_get_block().
1195	*
1196	* The LRUs themselves only need locking against invalidate_bh_lrus. We use
1197	* a local interrupt disable for that.
1198	*/
1199
1200	#define BH_LRU_SIZE 16
1201
1202	struct bh_lru {
1203	struct buffer_head *bhs[BH_LRU_SIZE];
1204	};
1205
1206	static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1207
1208	#ifdef CONFIG_SMP
1209	#define bh_lru_lock() local_irq_disable()
1210	#define bh_lru_unlock() local_irq_enable()
1211	#else
1212	#define bh_lru_lock() preempt_disable()
1213	#define bh_lru_unlock() preempt_enable()
1214	#endif
1215
1216	static inline void check_irqs_on(void)
1217	{
1218	#ifdef irqs_disabled
1219	BUG_ON(irqs_disabled());
1220	#endif
1221	}
1222
1223	/*
1224	* Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1225	* inserted at the front, and the buffer_head at the back if any is evicted.
1226	* Or, if already in the LRU it is moved to the front.
1227	*/
1228	static void bh_lru_install(struct buffer_head *bh)
1229	{
1230	struct buffer_head *evictee = bh;
1231	struct bh_lru *b;
1232	int i;
1233
1234	check_irqs_on();
1235	bh_lru_lock();
1236
1237	/*
1238	* the refcount of buffer_head in bh_lru prevents dropping the
1239	* attached page(i.e., try_to_free_buffers) so it could cause
1240	* failing page migration.
1241	* Skip putting upcoming bh into bh_lru until migration is done.
1242	*/
1243	if (lru_cache_disabled()) {
1244	bh_lru_unlock();
1245	return;
1246	}
1247
1248	b = this_cpu_ptr(&bh_lrus);
1249	for (i = 0; i < BH_LRU_SIZE; i++) {
1250	swap(evictee, b->bhs[i]);
1251	if (evictee == bh) {
1252	bh_lru_unlock();
1253	return;
1254	}
1255	}
1256
1257	get_bh(bh);
1258	bh_lru_unlock();
1259	brelse(evictee);
1260	}
1261
1262	/*
1263	* Look up the bh in this cpu's LRU. If it's there, move it to the head.
1264	*/
1265	static struct buffer_head *
1266	lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1267	{
1268	struct buffer_head *ret = NULL;
1269	unsigned int i;
1270
1271	check_irqs_on();
1272	bh_lru_lock();
1273	for (i = 0; i < BH_LRU_SIZE; i++) {
1274	struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1275
1276	if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1277	bh->b_size == size) {
1278	if (i) {
1279	while (i) {
1280	__this_cpu_write(bh_lrus.bhs[i],
1281	__this_cpu_read(bh_lrus.bhs[i - 1]));
1282	i--;
1283	}
1284	__this_cpu_write(bh_lrus.bhs[0], bh);
1285	}
1286	get_bh(bh);
1287	ret = bh;
1288	break;
1289	}
1290	}
1291	bh_lru_unlock();
1292	return ret;
1293	}
1294
1295	/*
1296	* Perform a pagecache lookup for the matching buffer. If it's there, refresh
1297	* it in the LRU and mark it as accessed. If it is not present then return
1298	* NULL
1299	*/
1300	struct buffer_head *
1301	__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1302	{
1303	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1304
1305	if (bh == NULL) {
1306	/* __find_get_block_slow will mark the page accessed */
1307	bh = __find_get_block_slow(bdev, block);
1308	if (bh)
1309	bh_lru_install(bh);
1310	} else
1311	touch_buffer(bh);
1312
1313	return bh;
1314	}
1315	EXPORT_SYMBOL(__find_get_block);
1316
1317	/*
1318	* __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1319	* which corresponds to the passed block_device, block and size. The
1320	* returned buffer has its reference count incremented.
1321	*
1322	* __getblk_gfp() will lock up the machine if grow_dev_page's
1323	* try_to_free_buffers() attempt is failing. FIXME, perhaps?
1324	*/
1325	struct buffer_head *
1326	__getblk_gfp(struct block_device *bdev, sector_t block,
1327	unsigned size, gfp_t gfp)
1328	{
1329	struct buffer_head *bh = __find_get_block(bdev, block, size);
1330
1331	might_sleep();
1332	if (bh == NULL)
1333	bh = __getblk_slow(bdev, block, size, gfp);
1334	return bh;
1335	}
1336	EXPORT_SYMBOL(__getblk_gfp);
1337
1338	/*
1339	* Do async read-ahead on a buffer..
1340	*/
1341	void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1342	{
1343	struct buffer_head *bh = __getblk(bdev, block, size);
1344	if (likely(bh)) {
1345	ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
1346	brelse(bh);
1347	}
1348	}
1349	EXPORT_SYMBOL(__breadahead);
1350
1351	void __breadahead_gfp(struct block_device *bdev, sector_t block, unsigned size,
1352	gfp_t gfp)
1353	{
1354	struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1355	if (likely(bh)) {
1356	ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
1357	brelse(bh);
1358	}
1359	}
1360	EXPORT_SYMBOL(__breadahead_gfp);
1361
1362	/**
1363	* __bread_gfp() - reads a specified block and returns the bh
1364	* @bdev: the block_device to read from
1365	* @block: number of block
1366	* @size: size (in bytes) to read
1367	* @gfp: page allocation flag
1368	*
1369	* Reads a specified block, and returns buffer head that contains it.
1370	* The page cache can be allocated from non-movable area
1371	* not to prevent page migration if you set gfp to zero.
1372	* It returns NULL if the block was unreadable.
1373	*/
1374	struct buffer_head *
1375	__bread_gfp(struct block_device *bdev, sector_t block,
1376	unsigned size, gfp_t gfp)
1377	{
1378	struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1379
1380	if (likely(bh) && !buffer_uptodate(bh))
1381	bh = __bread_slow(bh);
1382	return bh;
1383	}
1384	EXPORT_SYMBOL(__bread_gfp);
1385
1386	static void __invalidate_bh_lrus(struct bh_lru *b)
1387	{
1388	int i;
1389
1390	for (i = 0; i < BH_LRU_SIZE; i++) {
1391	brelse(b->bhs[i]);
1392	b->bhs[i] = NULL;
1393	}
1394	}
1395	/*
1396	* invalidate_bh_lrus() is called rarely - but not only at unmount.
1397	* This doesn't race because it runs in each cpu either in irq
1398	* or with preempt disabled.
1399	*/
1400	static void invalidate_bh_lru(void *arg)
1401	{
1402	struct bh_lru *b = &get_cpu_var(bh_lrus);
1403
1404	__invalidate_bh_lrus(b);
1405	put_cpu_var(bh_lrus);
1406	}
1407
1408	bool has_bh_in_lru(int cpu, void *dummy)
1409	{
1410	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1411	int i;
1412
1413	for (i = 0; i < BH_LRU_SIZE; i++) {
1414	if (b->bhs[i])
1415	return true;
1416	}
1417
1418	return false;
1419	}
1420
1421	void invalidate_bh_lrus(void)
1422	{
1423	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1);
1424	}
1425	EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1426
1427	/*
1428	* It's called from workqueue context so we need a bh_lru_lock to close
1429	* the race with preemption/irq.
1430	*/
1431	void invalidate_bh_lrus_cpu(void)
1432	{
1433	struct bh_lru *b;
1434
1435	bh_lru_lock();
1436	b = this_cpu_ptr(&bh_lrus);
1437	__invalidate_bh_lrus(b);
1438	bh_lru_unlock();
1439	}
1440
1441	void set_bh_page(struct buffer_head *bh,
1442	struct page *page, unsigned long offset)
1443	{
1444	bh->b_page = page;
1445	BUG_ON(offset >= PAGE_SIZE);
1446	if (PageHighMem(page))
1447	/*
1448	* This catches illegal uses and preserves the offset:
1449	*/
1450	bh->b_data = (char *)(0 + offset);
1451	else
1452	bh->b_data = page_address(page) + offset;
1453	}
1454	EXPORT_SYMBOL(set_bh_page);
1455
1456	/*
1457	* Called when truncating a buffer on a page completely.
1458	*/
1459
1460	/* Bits that are cleared during an invalidate */
1461	#define BUFFER_FLAGS_DISCARD \
1462	(1 << BH_Mapped \| 1 << BH_New \| 1 << BH_Req \| \
1463	1 << BH_Delay \| 1 << BH_Unwritten)
1464
1465	static void discard_buffer(struct buffer_head * bh)
1466	{
1467	unsigned long b_state, b_state_old;
1468
1469	lock_buffer(bh);
1470	clear_buffer_dirty(bh);
1471	bh->b_bdev = NULL;
1472	b_state = bh->b_state;
1473	for (;;) {
1474	b_state_old = cmpxchg(&bh->b_state, b_state,
1475	(b_state & ~BUFFER_FLAGS_DISCARD));
1476	if (b_state_old == b_state)
1477	break;
1478	b_state = b_state_old;
1479	}
1480	unlock_buffer(bh);
1481	}
1482
1483	/**
1484	* block_invalidate_folio - Invalidate part or all of a buffer-backed folio.
1485	* @folio: The folio which is affected.
1486	* @offset: start of the range to invalidate
1487	* @length: length of the range to invalidate
1488	*
1489	* block_invalidate_folio() is called when all or part of the folio has been
1490	* invalidated by a truncate operation.
1491	*
1492	* block_invalidate_folio() does not have to release all buffers, but it must
1493	* ensure that no dirty buffer is left outside @offset and that no I/O
1494	* is underway against any of the blocks which are outside the truncation
1495	* point. Because the caller is about to free (and possibly reuse) those
1496	* blocks on-disk.
1497	*/
1498	void block_invalidate_folio(struct folio *folio, size_t offset, size_t length)
1499	{
1500	struct buffer_head head, bh, *next;
1501	size_t curr_off = 0;
1502	size_t stop = length + offset;
1503
1504	BUG_ON(!folio_test_locked(folio));
1505
1506	/*
1507	* Check for overflow
1508	*/
1509	BUG_ON(stop > folio_size(folio) \|\| stop < length);
1510
1511	head = folio_buffers(folio);
1512	if (!head)
1513	return;
1514
1515	bh = head;
1516	do {
1517	size_t next_off = curr_off + bh->b_size;
1518	next = bh->b_this_page;
1519
1520	/*
1521	* Are we still fully in range ?
1522	*/
1523	if (next_off > stop)
1524	goto out;
1525
1526	/*
1527	* is this block fully invalidated?
1528	*/
1529	if (offset <= curr_off)
1530	discard_buffer(bh);
1531	curr_off = next_off;
1532	bh = next;
1533	} while (bh != head);
1534
1535	/*
1536	* We release buffers only if the entire folio is being invalidated.
1537	* The get_block cached value has been unconditionally invalidated,
1538	* so real IO is not possible anymore.
1539	*/
1540	if (length == folio_size(folio))
1541	filemap_release_folio(folio, 0);
1542	out:
1543	return;
1544	}
1545	EXPORT_SYMBOL(block_invalidate_folio);
1546
1547
1548	/*
1549	* We attach and possibly dirty the buffers atomically wrt
1550	* block_dirty_folio() via private_lock. try_to_free_buffers
1551	* is already excluded via the page lock.
1552	*/
1553	void create_empty_buffers(struct page *page,
1554	unsigned long blocksize, unsigned long b_state)
1555	{
1556	struct buffer_head bh, head, *tail;
1557
1558	head = alloc_page_buffers(page, blocksize, true);
1559	bh = head;
1560	do {
1561	bh->b_state \|= b_state;
1562	tail = bh;
1563	bh = bh->b_this_page;
1564	} while (bh);
1565	tail->b_this_page = head;
1566
1567	spin_lock(&page->mapping->private_lock);
1568	if (PageUptodate(page) \|\| PageDirty(page)) {
1569	bh = head;
1570	do {
1571	if (PageDirty(page))
1572	set_buffer_dirty(bh);
1573	if (PageUptodate(page))
1574	set_buffer_uptodate(bh);
1575	bh = bh->b_this_page;
1576	} while (bh != head);
1577	}
1578	attach_page_private(page, head);
1579	spin_unlock(&page->mapping->private_lock);
1580	}
1581	EXPORT_SYMBOL(create_empty_buffers);
1582
1583	/**
1584	* clean_bdev_aliases: clean a range of buffers in block device
1585	* @bdev: Block device to clean buffers in
1586	* @block: Start of a range of blocks to clean
1587	* @len: Number of blocks to clean
1588	*
1589	* We are taking a range of blocks for data and we don't want writeback of any
1590	* buffer-cache aliases starting from return from this function and until the
1591	* moment when something will explicitly mark the buffer dirty (hopefully that
1592	* will not happen until we will free that block ;-) We don't even need to mark
1593	* it not-uptodate - nobody can expect anything from a newly allocated buffer
1594	* anyway. We used to use unmap_buffer() for such invalidation, but that was
1595	* wrong. We definitely don't want to mark the alias unmapped, for example - it
1596	* would confuse anyone who might pick it with bread() afterwards...
1597	*
1598	* Also.. Note that bforget() doesn't lock the buffer. So there can be
1599	* writeout I/O going on against recently-freed buffers. We don't wait on that
1600	* I/O in bforget() - it's more efficient to wait on the I/O only if we really
1601	* need to. That happens here.
1602	*/
1603	void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1604	{
1605	struct inode *bd_inode = bdev->bd_inode;
1606	struct address_space *bd_mapping = bd_inode->i_mapping;
1607	struct pagevec pvec;
1608	pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
1609	pgoff_t end;
1610	int i, count;
1611	struct buffer_head *bh;
1612	struct buffer_head *head;
1613
1614	end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1615	pagevec_init(&pvec);
1616	while (pagevec_lookup_range(&pvec, bd_mapping, &index, end)) {
1617	count = pagevec_count(&pvec);
1618	for (i = 0; i < count; i++) {
1619	struct page *page = pvec.pages[i];
1620
1621	if (!page_has_buffers(page))
1622	continue;
1623	/*
1624	* We use page lock instead of bd_mapping->private_lock
1625	* to pin buffers here since we can afford to sleep and
1626	* it scales better than a global spinlock lock.
1627	*/
1628	lock_page(page);
1629	/* Recheck when the page is locked which pins bhs */
1630	if (!page_has_buffers(page))
1631	goto unlock_page;
1632	head = page_buffers(page);
1633	bh = head;
1634	do {
1635	if (!buffer_mapped(bh) \|\| (bh->b_blocknr < block))
1636	goto next;
1637	if (bh->b_blocknr >= block + len)
1638	break;
1639	clear_buffer_dirty(bh);
1640	wait_on_buffer(bh);
1641	clear_buffer_req(bh);
1642	next:
1643	bh = bh->b_this_page;
1644	} while (bh != head);
1645	unlock_page:
1646	unlock_page(page);
1647	}
1648	pagevec_release(&pvec);
1649	cond_resched();
1650	/* End of range already reached? */
1651	if (index > end \|\| !index)
1652	break;
1653	}
1654	}
1655	EXPORT_SYMBOL(clean_bdev_aliases);
1656
1657	/*
1658	* Size is a power-of-two in the range 512..PAGE_SIZE,
1659	* and the case we care about most is PAGE_SIZE.
1660	*
1661	* So this could possibly be written with those
1662	* constraints in mind (relevant mostly if some
1663	* architecture has a slow bit-scan instruction)
1664	*/
1665	static inline int block_size_bits(unsigned int blocksize)
1666	{
1667	return ilog2(blocksize);
1668	}
1669
1670	static struct buffer_head create_page_buffers(struct page page, struct inode *inode, unsigned int b_state)
1671	{
1672	BUG_ON(!PageLocked(page));
1673
1674	if (!page_has_buffers(page))
1675	create_empty_buffers(page, 1 << READ_ONCE(inode->i_blkbits),
1676	b_state);
1677	return page_buffers(page);
1678	}
1679
1680	/*
1681	* NOTE! All mapped/uptodate combinations are valid:
1682	*
1683	* Mapped Uptodate Meaning
1684	*
1685	* No No "unknown" - must do get_block()
1686	* No Yes "hole" - zero-filled
1687	* Yes No "allocated" - allocated on disk, not read in
1688	* Yes Yes "valid" - allocated and up-to-date in memory.
1689	*
1690	* "Dirty" is valid only with the last case (mapped+uptodate).
1691	*/
1692
1693	/*
1694	* While block_write_full_page is writing back the dirty buffers under
1695	* the page lock, whoever dirtied the buffers may decide to clean them
1696	* again at any time. We handle that by only looking at the buffer
1697	* state inside lock_buffer().
1698	*
1699	* If block_write_full_page() is called for regular writeback
1700	* (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1701	* locked buffer. This only can happen if someone has written the buffer
1702	* directly, with submit_bh(). At the address_space level PageWriteback
1703	* prevents this contention from occurring.
1704	*
1705	* If block_write_full_page() is called with wbc->sync_mode ==
1706	* WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1707	* causes the writes to be flagged as synchronous writes.
1708	*/
1709	int __block_write_full_page(struct inode inode, struct page page,
1710	get_block_t get_block, struct writeback_control wbc,
1711	bh_end_io_t *handler)
1712	{
1713	int err;
1714	sector_t block;
1715	sector_t last_block;
1716	struct buffer_head bh, head;
1717	unsigned int blocksize, bbits;
1718	int nr_underway = 0;
1719	int write_flags = wbc_to_write_flags(wbc);
1720
1721	head = create_page_buffers(page, inode,
1722	(1 << BH_Dirty)\|(1 << BH_Uptodate));
1723
1724	/*
1725	* Be very careful. We have no exclusion from block_dirty_folio
1726	* here, and the (potentially unmapped) buffers may become dirty at
1727	* any time. If a buffer becomes dirty here after we've inspected it
1728	* then we just miss that fact, and the page stays dirty.
1729	*
1730	* Buffers outside i_size may be dirtied by block_dirty_folio;
1731	* handle that here by just cleaning them.
1732	*/
1733
1734	bh = head;
1735	blocksize = bh->b_size;
1736	bbits = block_size_bits(blocksize);
1737
1738	block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1739	last_block = (i_size_read(inode) - 1) >> bbits;
1740
1741	/*
1742	* Get all the dirty buffers mapped to disk addresses and
1743	* handle any aliases from the underlying blockdev's mapping.
1744	*/
1745	do {
1746	if (block > last_block) {
1747	/*
1748	* mapped buffers outside i_size will occur, because
1749	* this page can be outside i_size when there is a
1750	* truncate in progress.
1751	*/
1752	/*
1753	* The buffer was zeroed by block_write_full_page()
1754	*/
1755	clear_buffer_dirty(bh);
1756	set_buffer_uptodate(bh);
1757	} else if ((!buffer_mapped(bh) \|\| buffer_delay(bh)) &&
1758	buffer_dirty(bh)) {
1759	WARN_ON(bh->b_size != blocksize);
1760	err = get_block(inode, block, bh, 1);
1761	if (err)
1762	goto recover;
1763	clear_buffer_delay(bh);
1764	if (buffer_new(bh)) {
1765	/* blockdev mappings never come here */
1766	clear_buffer_new(bh);
1767	clean_bdev_bh_alias(bh);
1768	}
1769	}
1770	bh = bh->b_this_page;
1771	block++;
1772	} while (bh != head);
1773
1774	do {
1775	if (!buffer_mapped(bh))
1776	continue;
1777	/*
1778	* If it's a fully non-blocking write attempt and we cannot
1779	* lock the buffer then redirty the page. Note that this can
1780	* potentially cause a busy-wait loop from writeback threads
1781	* and kswapd activity, but those code paths have their own
1782	* higher-level throttling.
1783	*/
1784	if (wbc->sync_mode != WB_SYNC_NONE) {
1785	lock_buffer(bh);
1786	} else if (!trylock_buffer(bh)) {
1787	redirty_page_for_writepage(wbc, page);
1788	continue;
1789	}
1790	if (test_clear_buffer_dirty(bh)) {
1791	mark_buffer_async_write_endio(bh, handler);
1792	} else {
1793	unlock_buffer(bh);
1794	}
1795	} while ((bh = bh->b_this_page) != head);
1796
1797	/*
1798	* The page and its buffers are protected by PageWriteback(), so we can
1799	* drop the bh refcounts early.
1800	*/
1801	BUG_ON(PageWriteback(page));
1802	set_page_writeback(page);
1803
1804	do {
1805	struct buffer_head *next = bh->b_this_page;
1806	if (buffer_async_write(bh)) {
1807	submit_bh_wbc(REQ_OP_WRITE, write_flags, bh, wbc);
1808	nr_underway++;
1809	}
1810	bh = next;
1811	} while (bh != head);
1812	unlock_page(page);
1813
1814	err = 0;
1815	done:
1816	if (nr_underway == 0) {
1817	/*
1818	* The page was marked dirty, but the buffers were
1819	* clean. Someone wrote them back by hand with
1820	* ll_rw_block/submit_bh. A rare case.
1821	*/
1822	end_page_writeback(page);
1823
1824	/*
1825	* The page and buffer_heads can be released at any time from
1826	* here on.
1827	*/
1828	}
1829	return err;
1830
1831	recover:
1832	/*
1833	* ENOSPC, or some other error. We may already have added some
1834	* blocks to the file, so we need to write these out to avoid
1835	* exposing stale data.
1836	* The page is currently locked and not marked for writeback
1837	*/
1838	bh = head;
1839	/* Recovery: lock and submit the mapped buffers */
1840	do {
1841	if (buffer_mapped(bh) && buffer_dirty(bh) &&
1842	!buffer_delay(bh)) {
1843	lock_buffer(bh);
1844	mark_buffer_async_write_endio(bh, handler);
1845	} else {
1846	/*
1847	* The buffer may have been set dirty during
1848	* attachment to a dirty page.
1849	*/
1850	clear_buffer_dirty(bh);
1851	}
1852	} while ((bh = bh->b_this_page) != head);
1853	SetPageError(page);
1854	BUG_ON(PageWriteback(page));
1855	mapping_set_error(page->mapping, err);
1856	set_page_writeback(page);
1857	do {
1858	struct buffer_head *next = bh->b_this_page;
1859	if (buffer_async_write(bh)) {
1860	clear_buffer_dirty(bh);
1861	submit_bh_wbc(REQ_OP_WRITE, write_flags, bh, wbc);
1862	nr_underway++;
1863	}
1864	bh = next;
1865	} while (bh != head);
1866	unlock_page(page);
1867	goto done;
1868	}
1869	EXPORT_SYMBOL(__block_write_full_page);
1870
1871	/*
1872	* If a page has any new buffers, zero them out here, and mark them uptodate
1873	* and dirty so they'll be written out (in order to prevent uninitialised
1874	* block data from leaking). And clear the new bit.
1875	*/
1876	void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1877	{
1878	unsigned int block_start, block_end;
1879	struct buffer_head head, bh;
1880
1881	BUG_ON(!PageLocked(page));
1882	if (!page_has_buffers(page))
1883	return;
1884
1885	bh = head = page_buffers(page);
1886	block_start = 0;
1887	do {
1888	block_end = block_start + bh->b_size;
1889
1890	if (buffer_new(bh)) {
1891	if (block_end > from && block_start < to) {
1892	if (!PageUptodate(page)) {
1893	unsigned start, size;
1894
1895	start = max(from, block_start);
1896	size = min(to, block_end) - start;
1897
1898	zero_user(page, start, size);
1899	set_buffer_uptodate(bh);
1900	}
1901
1902	clear_buffer_new(bh);
1903	mark_buffer_dirty(bh);
1904	}
1905	}
1906
1907	block_start = block_end;
1908	bh = bh->b_this_page;
1909	} while (bh != head);
1910	}
1911	EXPORT_SYMBOL(page_zero_new_buffers);
1912
1913	static void
1914	iomap_to_bh(struct inode inode, sector_t block, struct buffer_head bh,
1915	const struct iomap *iomap)
1916	{
1917	loff_t offset = block << inode->i_blkbits;
1918
1919	bh->b_bdev = iomap->bdev;
1920
1921	/*
1922	* Block points to offset in file we need to map, iomap contains
1923	* the offset at which the map starts. If the map ends before the
1924	* current block, then do not map the buffer and let the caller
1925	* handle it.
1926	*/
1927	BUG_ON(offset >= iomap->offset + iomap->length);
1928
1929	switch (iomap->type) {
1930	case IOMAP_HOLE:
1931	/*
1932	* If the buffer is not up to date or beyond the current EOF,
1933	* we need to mark it as new to ensure sub-block zeroing is
1934	* executed if necessary.
1935	*/
1936	if (!buffer_uptodate(bh) \|\|
1937	(offset >= i_size_read(inode)))
1938	set_buffer_new(bh);
1939	break;
1940	case IOMAP_DELALLOC:
1941	if (!buffer_uptodate(bh) \|\|
1942	(offset >= i_size_read(inode)))
1943	set_buffer_new(bh);
1944	set_buffer_uptodate(bh);
1945	set_buffer_mapped(bh);
1946	set_buffer_delay(bh);
1947	break;
1948	case IOMAP_UNWRITTEN:
1949	/*
1950	* For unwritten regions, we always need to ensure that regions
1951	* in the block we are not writing to are zeroed. Mark the
1952	* buffer as new to ensure this.
1953	*/
1954	set_buffer_new(bh);
1955	set_buffer_unwritten(bh);
1956	fallthrough;
1957	case IOMAP_MAPPED:
1958	if ((iomap->flags & IOMAP_F_NEW) \|\|
1959	offset >= i_size_read(inode))
1960	set_buffer_new(bh);
1961	bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
1962	inode->i_blkbits;
1963	set_buffer_mapped(bh);
1964	break;
1965	}
1966	}
1967
1968	int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len,
1969	get_block_t get_block, const struct iomap iomap)
1970	{
1971	unsigned from = pos & (PAGE_SIZE - 1);
1972	unsigned to = from + len;
1973	struct inode *inode = folio->mapping->host;
1974	unsigned block_start, block_end;
1975	sector_t block;
1976	int err = 0;
1977	unsigned blocksize, bbits;
1978	struct buffer_head bh, head, wait[2], *wait_bh=wait;
1979
1980	BUG_ON(!folio_test_locked(folio));
1981	BUG_ON(from > PAGE_SIZE);
1982	BUG_ON(to > PAGE_SIZE);
1983	BUG_ON(from > to);
1984
1985	head = create_page_buffers(&folio->page, inode, 0);
1986	blocksize = head->b_size;
1987	bbits = block_size_bits(blocksize);
1988
1989	block = (sector_t)folio->index << (PAGE_SHIFT - bbits);
1990
1991	for(bh = head, block_start = 0; bh != head \|\| !block_start;
1992	block++, block_start=block_end, bh = bh->b_this_page) {
1993	block_end = block_start + blocksize;
1994	if (block_end <= from \|\| block_start >= to) {
1995	if (folio_test_uptodate(folio)) {
1996	if (!buffer_uptodate(bh))
1997	set_buffer_uptodate(bh);
1998	}
1999	continue;
2000	}
2001	if (buffer_new(bh))
2002	clear_buffer_new(bh);
2003	if (!buffer_mapped(bh)) {
2004	WARN_ON(bh->b_size != blocksize);
2005	if (get_block) {
2006	err = get_block(inode, block, bh, 1);
2007	if (err)
2008	break;
2009	} else {
2010	iomap_to_bh(inode, block, bh, iomap);
2011	}
2012
2013	if (buffer_new(bh)) {
2014	clean_bdev_bh_alias(bh);
2015	if (folio_test_uptodate(folio)) {
2016	clear_buffer_new(bh);
2017	set_buffer_uptodate(bh);
2018	mark_buffer_dirty(bh);
2019	continue;
2020	}
2021	if (block_end > to \|\| block_start < from)
2022	folio_zero_segments(folio,
2023	to, block_end,
2024	block_start, from);
2025	continue;
2026	}
2027	}
2028	if (folio_test_uptodate(folio)) {
2029	if (!buffer_uptodate(bh))
2030	set_buffer_uptodate(bh);
2031	continue;
2032	}
2033	if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2034	!buffer_unwritten(bh) &&
2035	(block_start < from \|\| block_end > to)) {
2036	ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2037	*wait_bh++=bh;
2038	}
2039	}
2040	/*
2041	* If we issued read requests - let them complete.
2042	*/
2043	while(wait_bh > wait) {
2044	wait_on_buffer(*--wait_bh);
2045	if (!buffer_uptodate(*wait_bh))
2046	err = -EIO;
2047	}
2048	if (unlikely(err))
2049	page_zero_new_buffers(&folio->page, from, to);
2050	return err;
2051	}
2052
2053	int __block_write_begin(struct page *page, loff_t pos, unsigned len,
2054	get_block_t *get_block)
2055	{
2056	return __block_write_begin_int(page_folio(page), pos, len, get_block,
2057	NULL);
2058	}
2059	EXPORT_SYMBOL(__block_write_begin);
2060
2061	static int __block_commit_write(struct inode inode, struct page page,
2062	unsigned from, unsigned to)
2063	{
2064	unsigned block_start, block_end;
2065	int partial = 0;
2066	unsigned blocksize;
2067	struct buffer_head bh, head;
2068
2069	bh = head = page_buffers(page);
2070	blocksize = bh->b_size;
2071
2072	block_start = 0;
2073	do {
2074	block_end = block_start + blocksize;
2075	if (block_end <= from \|\| block_start >= to) {
2076	if (!buffer_uptodate(bh))
2077	partial = 1;
2078	} else {
2079	set_buffer_uptodate(bh);
2080	mark_buffer_dirty(bh);
2081	}
2082	if (buffer_new(bh))
2083	clear_buffer_new(bh);
2084
2085	block_start = block_end;
2086	bh = bh->b_this_page;
2087	} while (bh != head);
2088
2089	/*
2090	* If this is a partial write which happened to make all buffers
2091	* uptodate then we can optimize away a bogus readpage() for
2092	* the next read(). Here we 'discover' whether the page went
2093	* uptodate as a result of this (potentially partial) write.
2094	*/
2095	if (!partial)
2096	SetPageUptodate(page);
2097	return 0;
2098	}
2099
2100	/*
2101	* block_write_begin takes care of the basic task of block allocation and
2102	* bringing partial write blocks uptodate first.
2103	*
2104	* The filesystem needs to handle block truncation upon failure.
2105	*/
2106	int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2107	unsigned flags, struct page *pagep, get_block_t get_block)
2108	{
2109	pgoff_t index = pos >> PAGE_SHIFT;
2110	struct page *page;
2111	int status;
2112
2113	page = grab_cache_page_write_begin(mapping, index, flags);
2114	if (!page)
2115	return -ENOMEM;
2116
2117	status = __block_write_begin(page, pos, len, get_block);
2118	if (unlikely(status)) {
2119	unlock_page(page);
2120	put_page(page);
2121	page = NULL;
2122	}
2123
2124	*pagep = page;
2125	return status;
2126	}
2127	EXPORT_SYMBOL(block_write_begin);
2128
2129	int block_write_end(struct file file, struct address_space mapping,
2130	loff_t pos, unsigned len, unsigned copied,
2131	struct page page, void fsdata)
2132	{
2133	struct inode *inode = mapping->host;
2134	unsigned start;
2135
2136	start = pos & (PAGE_SIZE - 1);
2137
2138	if (unlikely(copied < len)) {
2139	/*
2140	* The buffers that were written will now be uptodate, so we
2141	* don't have to worry about a readpage reading them and
2142	* overwriting a partial write. However if we have encountered
2143	* a short write and only partially written into a buffer, it
2144	* will not be marked uptodate, so a readpage might come in and
2145	* destroy our partial write.
2146	*
2147	* Do the simplest thing, and just treat any short write to a
2148	* non uptodate page as a zero-length write, and force the
2149	* caller to redo the whole thing.
2150	*/
2151	if (!PageUptodate(page))
2152	copied = 0;
2153
2154	page_zero_new_buffers(page, start+copied, start+len);
2155	}
2156	flush_dcache_page(page);
2157
2158	/* This could be a short (even 0-length) commit */
2159	__block_commit_write(inode, page, start, start+copied);
2160
2161	return copied;
2162	}
2163	EXPORT_SYMBOL(block_write_end);
2164
2165	int generic_write_end(struct file file, struct address_space mapping,
2166	loff_t pos, unsigned len, unsigned copied,
2167	struct page page, void fsdata)
2168	{
2169	struct inode *inode = mapping->host;
2170	loff_t old_size = inode->i_size;
2171	bool i_size_changed = false;
2172
2173	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2174
2175	/*
2176	* No need to use i_size_read() here, the i_size cannot change under us
2177	* because we hold i_rwsem.
2178	*
2179	* But it's important to update i_size while still holding page lock:
2180	* page writeout could otherwise come in and zero beyond i_size.
2181	*/
2182	if (pos + copied > inode->i_size) {
2183	i_size_write(inode, pos + copied);
2184	i_size_changed = true;
2185	}
2186
2187	unlock_page(page);
2188	put_page(page);
2189
2190	if (old_size < pos)
2191	pagecache_isize_extended(inode, old_size, pos);
2192	/*
2193	* Don't mark the inode dirty under page lock. First, it unnecessarily
2194	* makes the holding time of page lock longer. Second, it forces lock
2195	* ordering of page lock and transaction start for journaling
2196	* filesystems.
2197	*/
2198	if (i_size_changed)
2199	mark_inode_dirty(inode);
2200	return copied;
2201	}
2202	EXPORT_SYMBOL(generic_write_end);
2203
2204	/*
2205	* block_is_partially_uptodate checks whether buffers within a folio are
2206	* uptodate or not.
2207	*
2208	* Returns true if all buffers which correspond to the specified part
2209	* of the folio are uptodate.
2210	*/
2211	bool block_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
2212	{
2213	unsigned block_start, block_end, blocksize;
2214	unsigned to;
2215	struct buffer_head bh, head;
2216	bool ret = true;
2217
2218	head = folio_buffers(folio);
2219	if (!head)
2220	return false;
2221	blocksize = head->b_size;
2222	to = min_t(unsigned, folio_size(folio) - from, count);
2223	to = from + to;
2224	if (from < blocksize && to > folio_size(folio) - blocksize)
2225	return false;
2226
2227	bh = head;
2228	block_start = 0;
2229	do {
2230	block_end = block_start + blocksize;
2231	if (block_end > from && block_start < to) {
2232	if (!buffer_uptodate(bh)) {
2233	ret = false;
2234	break;
2235	}
2236	if (block_end >= to)
2237	break;
2238	}
2239	block_start = block_end;
2240	bh = bh->b_this_page;
2241	} while (bh != head);
2242
2243	return ret;
2244	}
2245	EXPORT_SYMBOL(block_is_partially_uptodate);
2246
2247	/*
2248	* Generic "read page" function for block devices that have the normal
2249	* get_block functionality. This is most of the block device filesystems.
2250	* Reads the page asynchronously --- the unlock_buffer() and
2251	* set/clear_buffer_uptodate() functions propagate buffer state into the
2252	* page struct once IO has completed.
2253	*/
2254	int block_read_full_page(struct page page, get_block_t get_block)
2255	{
2256	struct inode *inode = page->mapping->host;
2257	sector_t iblock, lblock;
2258	struct buffer_head bh, head, *arr[MAX_BUF_PER_PAGE];
2259	unsigned int blocksize, bbits;
2260	int nr, i;
2261	int fully_mapped = 1;
2262
2263	head = create_page_buffers(page, inode, 0);
2264	blocksize = head->b_size;
2265	bbits = block_size_bits(blocksize);
2266
2267	iblock = (sector_t)page->index << (PAGE_SHIFT - bbits);
2268	lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2269	bh = head;
2270	nr = 0;
2271	i = 0;
2272
2273	do {
2274	if (buffer_uptodate(bh))
2275	continue;
2276
2277	if (!buffer_mapped(bh)) {
2278	int err = 0;
2279
2280	fully_mapped = 0;
2281	if (iblock < lblock) {
2282	WARN_ON(bh->b_size != blocksize);
2283	err = get_block(inode, iblock, bh, 0);
2284	if (err)
2285	SetPageError(page);
2286	}
2287	if (!buffer_mapped(bh)) {
2288	zero_user(page, i * blocksize, blocksize);
2289	if (!err)
2290	set_buffer_uptodate(bh);
2291	continue;
2292	}
2293	/*
2294	* get_block() might have updated the buffer
2295	* synchronously
2296	*/
2297	if (buffer_uptodate(bh))
2298	continue;
2299	}
2300	arr[nr++] = bh;
2301	} while (i++, iblock++, (bh = bh->b_this_page) != head);
2302
2303	if (fully_mapped)
2304	SetPageMappedToDisk(page);
2305
2306	if (!nr) {
2307	/*
2308	* All buffers are uptodate - we can set the page uptodate
2309	* as well. But not if get_block() returned an error.
2310	*/
2311	if (!PageError(page))
2312	SetPageUptodate(page);
2313	unlock_page(page);
2314	return 0;
2315	}
2316
2317	/* Stage two: lock the buffers */
2318	for (i = 0; i < nr; i++) {
2319	bh = arr[i];
2320	lock_buffer(bh);
2321	mark_buffer_async_read(bh);
2322	}
2323
2324	/*
2325	* Stage 3: start the IO. Check for uptodateness
2326	* inside the buffer lock in case another process reading
2327	* the underlying blockdev brought it uptodate (the sct fix).
2328	*/
2329	for (i = 0; i < nr; i++) {
2330	bh = arr[i];
2331	if (buffer_uptodate(bh))
2332	end_buffer_async_read(bh, 1);
2333	else
2334	submit_bh(REQ_OP_READ, 0, bh);
2335	}
2336	return 0;
2337	}
2338	EXPORT_SYMBOL(block_read_full_page);
2339
2340	/* utility function for filesystems that need to do work on expanding
2341	* truncates. Uses filesystem pagecache writes to allow the filesystem to
2342	* deal with the hole.
2343	*/
2344	int generic_cont_expand_simple(struct inode *inode, loff_t size)
2345	{
2346	struct address_space *mapping = inode->i_mapping;
2347	struct page *page;
2348	void *fsdata;
2349	int err;
2350
2351	err = inode_newsize_ok(inode, size);
2352	if (err)
2353	goto out;
2354
2355	err = pagecache_write_begin(NULL, mapping, size, 0, 0, &page, &fsdata);
2356	if (err)
2357	goto out;
2358
2359	err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2360	BUG_ON(err > 0);
2361
2362	out:
2363	return err;
2364	}
2365	EXPORT_SYMBOL(generic_cont_expand_simple);
2366
2367	static int cont_expand_zero(struct file file, struct address_space mapping,
2368	loff_t pos, loff_t *bytes)
2369	{
2370	struct inode *inode = mapping->host;
2371	unsigned int blocksize = i_blocksize(inode);
2372	struct page *page;
2373	void *fsdata;
2374	pgoff_t index, curidx;
2375	loff_t curpos;
2376	unsigned zerofrom, offset, len;
2377	int err = 0;
2378
2379	index = pos >> PAGE_SHIFT;
2380	offset = pos & ~PAGE_MASK;
2381
2382	while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2383	zerofrom = curpos & ~PAGE_MASK;
2384	if (zerofrom & (blocksize-1)) {
2385	*bytes \|= (blocksize-1);
2386	(*bytes)++;
2387	}
2388	len = PAGE_SIZE - zerofrom;
2389
2390	err = pagecache_write_begin(file, mapping, curpos, len, 0,
2391	&page, &fsdata);
2392	if (err)
2393	goto out;
2394	zero_user(page, zerofrom, len);
2395	err = pagecache_write_end(file, mapping, curpos, len, len,
2396	page, fsdata);
2397	if (err < 0)
2398	goto out;
2399	BUG_ON(err != len);
2400	err = 0;
2401
2402	balance_dirty_pages_ratelimited(mapping);
2403
2404	if (fatal_signal_pending(current)) {
2405	err = -EINTR;
2406	goto out;
2407	}
2408	}
2409
2410	/* page covers the boundary, find the boundary offset */
2411	if (index == curidx) {
2412	zerofrom = curpos & ~PAGE_MASK;
2413	/* if we will expand the thing last block will be filled */
2414	if (offset <= zerofrom) {
2415	goto out;
2416	}
2417	if (zerofrom & (blocksize-1)) {
2418	*bytes \|= (blocksize-1);
2419	(*bytes)++;
2420	}
2421	len = offset - zerofrom;
2422
2423	err = pagecache_write_begin(file, mapping, curpos, len, 0,
2424	&page, &fsdata);
2425	if (err)
2426	goto out;
2427	zero_user(page, zerofrom, len);
2428	err = pagecache_write_end(file, mapping, curpos, len, len,
2429	page, fsdata);
2430	if (err < 0)
2431	goto out;
2432	BUG_ON(err != len);
2433	err = 0;
2434	}
2435	out:
2436	return err;
2437	}
2438
2439	/*
2440	* For moronic filesystems that do not allow holes in file.
2441	* We may have to extend the file.
2442	*/
2443	int cont_write_begin(struct file file, struct address_space mapping,
2444	loff_t pos, unsigned len, unsigned flags,
2445	struct page pagep, void fsdata,
2446	get_block_t get_block, loff_t bytes)
2447	{
2448	struct inode *inode = mapping->host;
2449	unsigned int blocksize = i_blocksize(inode);
2450	unsigned int zerofrom;
2451	int err;
2452
2453	err = cont_expand_zero(file, mapping, pos, bytes);
2454	if (err)
2455	return err;
2456
2457	zerofrom = *bytes & ~PAGE_MASK;
2458	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2459	*bytes \|= (blocksize-1);
2460	(*bytes)++;
2461	}
2462
2463	return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2464	}
2465	EXPORT_SYMBOL(cont_write_begin);
2466
2467	int block_commit_write(struct page *page, unsigned from, unsigned to)
2468	{
2469	struct inode *inode = page->mapping->host;
2470	__block_commit_write(inode,page,from,to);
2471	return 0;
2472	}
2473	EXPORT_SYMBOL(block_commit_write);
2474
2475	/*
2476	* block_page_mkwrite() is not allowed to change the file size as it gets
2477	* called from a page fault handler when a page is first dirtied. Hence we must
2478	* be careful to check for EOF conditions here. We set the page up correctly
2479	* for a written page which means we get ENOSPC checking when writing into
2480	* holes and correct delalloc and unwritten extent mapping on filesystems that
2481	* support these features.
2482	*
2483	* We are not allowed to take the i_mutex here so we have to play games to
2484	* protect against truncate races as the page could now be beyond EOF. Because
2485	* truncate writes the inode size before removing pages, once we have the
2486	* page lock we can determine safely if the page is beyond EOF. If it is not
2487	* beyond EOF, then the page is guaranteed safe against truncation until we
2488	* unlock the page.
2489	*
2490	* Direct callers of this function should protect against filesystem freezing
2491	* using sb_start_pagefault() - sb_end_pagefault() functions.
2492	*/
2493	int block_page_mkwrite(struct vm_area_struct vma, struct vm_fault vmf,
2494	get_block_t get_block)
2495	{
2496	struct page *page = vmf->page;
2497	struct inode *inode = file_inode(vma->vm_file);
2498	unsigned long end;
2499	loff_t size;
2500	int ret;
2501
2502	lock_page(page);
2503	size = i_size_read(inode);
2504	if ((page->mapping != inode->i_mapping) \|\|
2505	(page_offset(page) > size)) {
2506	/* We overload EFAULT to mean page got truncated */
2507	ret = -EFAULT;
2508	goto out_unlock;
2509	}
2510
2511	/* page is wholly or partially inside EOF */
2512	if (((page->index + 1) << PAGE_SHIFT) > size)
2513	end = size & ~PAGE_MASK;
2514	else
2515	end = PAGE_SIZE;
2516
2517	ret = __block_write_begin(page, 0, end, get_block);
2518	if (!ret)
2519	ret = block_commit_write(page, 0, end);
2520
2521	if (unlikely(ret < 0))
2522	goto out_unlock;
2523	set_page_dirty(page);
2524	wait_for_stable_page(page);
2525	return 0;
2526	out_unlock:
2527	unlock_page(page);
2528	return ret;
2529	}
2530	EXPORT_SYMBOL(block_page_mkwrite);
2531
2532	/*
2533	* nobh_write_begin()'s prereads are special: the buffer_heads are freed
2534	* immediately, while under the page lock. So it needs a special end_io
2535	* handler which does not touch the bh after unlocking it.
2536	*/
2537	static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2538	{
2539	__end_buffer_read_notouch(bh, uptodate);
2540	}
2541
2542	/*
2543	* Attach the singly-linked list of buffers created by nobh_write_begin, to
2544	* the page (converting it to circular linked list and taking care of page
2545	* dirty races).
2546	*/
2547	static void attach_nobh_buffers(struct page page, struct buffer_head head)
2548	{
2549	struct buffer_head *bh;
2550
2551	BUG_ON(!PageLocked(page));
2552
2553	spin_lock(&page->mapping->private_lock);
2554	bh = head;
2555	do {
2556	if (PageDirty(page))
2557	set_buffer_dirty(bh);
2558	if (!bh->b_this_page)
2559	bh->b_this_page = head;
2560	bh = bh->b_this_page;
2561	} while (bh != head);
2562	attach_page_private(page, head);
2563	spin_unlock(&page->mapping->private_lock);
2564	}
2565
2566	/*
2567	* On entry, the page is fully not uptodate.
2568	* On exit the page is fully uptodate in the areas outside (from,to)
2569	* The filesystem needs to handle block truncation upon failure.
2570	*/
2571	int nobh_write_begin(struct address_space *mapping,
2572	loff_t pos, unsigned len, unsigned flags,
2573	struct page pagep, void fsdata,
2574	get_block_t *get_block)
2575	{
2576	struct inode *inode = mapping->host;
2577	const unsigned blkbits = inode->i_blkbits;
2578	const unsigned blocksize = 1 << blkbits;
2579	struct buffer_head head, bh;
2580	struct page *page;
2581	pgoff_t index;
2582	unsigned from, to;
2583	unsigned block_in_page;
2584	unsigned block_start, block_end;
2585	sector_t block_in_file;
2586	int nr_reads = 0;
2587	int ret = 0;
2588	int is_mapped_to_disk = 1;
2589
2590	index = pos >> PAGE_SHIFT;
2591	from = pos & (PAGE_SIZE - 1);
2592	to = from + len;
2593
2594	page = grab_cache_page_write_begin(mapping, index, flags);
2595	if (!page)
2596	return -ENOMEM;
2597	*pagep = page;
2598	*fsdata = NULL;
2599
2600	if (page_has_buffers(page)) {
2601	ret = __block_write_begin(page, pos, len, get_block);
2602	if (unlikely(ret))
2603	goto out_release;
2604	return ret;
2605	}
2606
2607	if (PageMappedToDisk(page))
2608	return 0;
2609
2610	/*
2611	* Allocate buffers so that we can keep track of state, and potentially
2612	* attach them to the page if an error occurs. In the common case of
2613	* no error, they will just be freed again without ever being attached
2614	* to the page (which is all OK, because we're under the page lock).
2615	*
2616	* Be careful: the buffer linked list is a NULL terminated one, rather
2617	* than the circular one we're used to.
2618	*/
2619	head = alloc_page_buffers(page, blocksize, false);
2620	if (!head) {
2621	ret = -ENOMEM;
2622	goto out_release;
2623	}
2624
2625	block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
2626
2627	/*
2628	* We loop across all blocks in the page, whether or not they are
2629	* part of the affected region. This is so we can discover if the
2630	* page is fully mapped-to-disk.
2631	*/
2632	for (block_start = 0, block_in_page = 0, bh = head;
2633	block_start < PAGE_SIZE;
2634	block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2635	int create;
2636
2637	block_end = block_start + blocksize;
2638	bh->b_state = 0;
2639	create = 1;
2640	if (block_start >= to)
2641	create = 0;
2642	ret = get_block(inode, block_in_file + block_in_page,
2643	bh, create);
2644	if (ret)
2645	goto failed;
2646	if (!buffer_mapped(bh))
2647	is_mapped_to_disk = 0;
2648	if (buffer_new(bh))
2649	clean_bdev_bh_alias(bh);
2650	if (PageUptodate(page)) {
2651	set_buffer_uptodate(bh);
2652	continue;
2653	}
2654	if (buffer_new(bh) \|\| !buffer_mapped(bh)) {
2655	zero_user_segments(page, block_start, from,
2656	to, block_end);
2657	continue;
2658	}
2659	if (buffer_uptodate(bh))
2660	continue; /* reiserfs does this */
2661	if (block_start < from \|\| block_end > to) {
2662	lock_buffer(bh);
2663	bh->b_end_io = end_buffer_read_nobh;
2664	submit_bh(REQ_OP_READ, 0, bh);
2665	nr_reads++;
2666	}
2667	}
2668
2669	if (nr_reads) {
2670	/*
2671	* The page is locked, so these buffers are protected from
2672	* any VM or truncate activity. Hence we don't need to care
2673	* for the buffer_head refcounts.
2674	*/
2675	for (bh = head; bh; bh = bh->b_this_page) {
2676	wait_on_buffer(bh);
2677	if (!buffer_uptodate(bh))
2678	ret = -EIO;
2679	}
2680	if (ret)
2681	goto failed;
2682	}
2683
2684	if (is_mapped_to_disk)
2685	SetPageMappedToDisk(page);
2686
2687	fsdata = head; / to be released by nobh_write_end */
2688
2689	return 0;
2690
2691	failed:
2692	BUG_ON(!ret);
2693	/*
2694	* Error recovery is a bit difficult. We need to zero out blocks that
2695	* were newly allocated, and dirty them to ensure they get written out.
2696	* Buffers need to be attached to the page at this point, otherwise
2697	* the handling of potential IO errors during writeout would be hard
2698	* (could try doing synchronous writeout, but what if that fails too?)
2699	*/
2700	attach_nobh_buffers(page, head);
2701	page_zero_new_buffers(page, from, to);
2702
2703	out_release:
2704	unlock_page(page);
2705	put_page(page);
2706	*pagep = NULL;
2707
2708	return ret;
2709	}
2710	EXPORT_SYMBOL(nobh_write_begin);
2711
2712	int nobh_write_end(struct file file, struct address_space mapping,
2713	loff_t pos, unsigned len, unsigned copied,
2714	struct page page, void fsdata)
2715	{
2716	struct inode *inode = page->mapping->host;
2717	struct buffer_head *head = fsdata;
2718	struct buffer_head *bh;
2719	BUG_ON(fsdata != NULL && page_has_buffers(page));
2720
2721	if (unlikely(copied < len) && head)
2722	attach_nobh_buffers(page, head);
2723	if (page_has_buffers(page))
2724	return generic_write_end(file, mapping, pos, len,
2725	copied, page, fsdata);
2726
2727	SetPageUptodate(page);
2728	set_page_dirty(page);
2729	if (pos+copied > inode->i_size) {
2730	i_size_write(inode, pos+copied);
2731	mark_inode_dirty(inode);
2732	}
2733
2734	unlock_page(page);
2735	put_page(page);
2736
2737	while (head) {
2738	bh = head;
2739	head = head->b_this_page;
2740	free_buffer_head(bh);
2741	}
2742
2743	return copied;
2744	}
2745	EXPORT_SYMBOL(nobh_write_end);
2746
2747	/*
2748	* nobh_writepage() - based on block_full_write_page() except
2749	* that it tries to operate without attaching bufferheads to
2750	* the page.
2751	*/
2752	int nobh_writepage(struct page page, get_block_t get_block,
2753	struct writeback_control *wbc)
2754	{
2755	struct inode * const inode = page->mapping->host;
2756	loff_t i_size = i_size_read(inode);
2757	const pgoff_t end_index = i_size >> PAGE_SHIFT;
2758	unsigned offset;
2759	int ret;
2760
2761	/* Is the page fully inside i_size? */
2762	if (page->index < end_index)
2763	goto out;
2764
2765	/* Is the page fully outside i_size? (truncate in progress) */
2766	offset = i_size & (PAGE_SIZE-1);
2767	if (page->index >= end_index+1 \|\| !offset) {
2768	unlock_page(page);
2769	return 0; /* don't care */
2770	}
2771
2772	/*
2773	* The page straddles i_size. It must be zeroed out on each and every
2774	* writepage invocation because it may be mmapped. "A file is mapped
2775	* in multiples of the page size. For a file that is not a multiple of
2776	* the page size, the remaining memory is zeroed when mapped, and
2777	* writes to that region are not written out to the file."
2778	*/
2779	zero_user_segment(page, offset, PAGE_SIZE);
2780	out:
2781	ret = mpage_writepage(page, get_block, wbc);
2782	if (ret == -EAGAIN)
2783	ret = __block_write_full_page(inode, page, get_block, wbc,
2784	end_buffer_async_write);
2785	return ret;
2786	}
2787	EXPORT_SYMBOL(nobh_writepage);
2788
2789	int nobh_truncate_page(struct address_space *mapping,
2790	loff_t from, get_block_t *get_block)
2791	{
2792	pgoff_t index = from >> PAGE_SHIFT;
2793	unsigned offset = from & (PAGE_SIZE-1);
2794	unsigned blocksize;
2795	sector_t iblock;
2796	unsigned length, pos;
2797	struct inode *inode = mapping->host;
2798	struct page *page;
2799	struct buffer_head map_bh;
2800	int err;
2801
2802	blocksize = i_blocksize(inode);
2803	length = offset & (blocksize - 1);
2804
2805	/* Block boundary? Nothing to do */
2806	if (!length)
2807	return 0;
2808
2809	length = blocksize - length;
2810	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2811
2812	page = grab_cache_page(mapping, index);
2813	err = -ENOMEM;
2814	if (!page)
2815	goto out;
2816
2817	if (page_has_buffers(page)) {
2818	has_buffers:
2819	unlock_page(page);
2820	put_page(page);
2821	return block_truncate_page(mapping, from, get_block);
2822	}
2823
2824	/* Find the buffer that contains "offset" */
2825	pos = blocksize;
2826	while (offset >= pos) {
2827	iblock++;
2828	pos += blocksize;
2829	}
2830
2831	map_bh.b_size = blocksize;
2832	map_bh.b_state = 0;
2833	err = get_block(inode, iblock, &map_bh, 0);
2834	if (err)
2835	goto unlock;
2836	/* unmapped? It's a hole - nothing to do */
2837	if (!buffer_mapped(&map_bh))
2838	goto unlock;
2839
2840	/* Ok, it's mapped. Make sure it's up-to-date */
2841	if (!PageUptodate(page)) {
2842	err = mapping->a_ops->readpage(NULL, page);
2843	if (err) {
2844	put_page(page);
2845	goto out;
2846	}
2847	lock_page(page);
2848	if (!PageUptodate(page)) {
2849	err = -EIO;
2850	goto unlock;
2851	}
2852	if (page_has_buffers(page))
2853	goto has_buffers;
2854	}
2855	zero_user(page, offset, length);
2856	set_page_dirty(page);
2857	err = 0;
2858
2859	unlock:
2860	unlock_page(page);
2861	put_page(page);
2862	out:
2863	return err;
2864	}
2865	EXPORT_SYMBOL(nobh_truncate_page);
2866
2867	int block_truncate_page(struct address_space *mapping,
2868	loff_t from, get_block_t *get_block)
2869	{
2870	pgoff_t index = from >> PAGE_SHIFT;
2871	unsigned offset = from & (PAGE_SIZE-1);
2872	unsigned blocksize;
2873	sector_t iblock;
2874	unsigned length, pos;
2875	struct inode *inode = mapping->host;
2876	struct page *page;
2877	struct buffer_head *bh;
2878	int err;
2879
2880	blocksize = i_blocksize(inode);
2881	length = offset & (blocksize - 1);
2882
2883	/* Block boundary? Nothing to do */
2884	if (!length)
2885	return 0;
2886
2887	length = blocksize - length;
2888	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2889
2890	page = grab_cache_page(mapping, index);
2891	err = -ENOMEM;
2892	if (!page)
2893	goto out;
2894
2895	if (!page_has_buffers(page))
2896	create_empty_buffers(page, blocksize, 0);
2897
2898	/* Find the buffer that contains "offset" */
2899	bh = page_buffers(page);
2900	pos = blocksize;
2901	while (offset >= pos) {
2902	bh = bh->b_this_page;
2903	iblock++;
2904	pos += blocksize;
2905	}
2906
2907	err = 0;
2908	if (!buffer_mapped(bh)) {
2909	WARN_ON(bh->b_size != blocksize);
2910	err = get_block(inode, iblock, bh, 0);
2911	if (err)
2912	goto unlock;
2913	/* unmapped? It's a hole - nothing to do */
2914	if (!buffer_mapped(bh))
2915	goto unlock;
2916	}
2917
2918	/* Ok, it's mapped. Make sure it's up-to-date */
2919	if (PageUptodate(page))
2920	set_buffer_uptodate(bh);
2921
2922	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2923	err = -EIO;
2924	ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2925	wait_on_buffer(bh);
2926	/* Uhhuh. Read error. Complain and punt. */
2927	if (!buffer_uptodate(bh))
2928	goto unlock;
2929	}
2930
2931	zero_user(page, offset, length);
2932	mark_buffer_dirty(bh);
2933	err = 0;
2934
2935	unlock:
2936	unlock_page(page);
2937	put_page(page);
2938	out:
2939	return err;
2940	}
2941	EXPORT_SYMBOL(block_truncate_page);
2942
2943	/*
2944	* The generic ->writepage function for buffer-backed address_spaces
2945	*/
2946	int block_write_full_page(struct page page, get_block_t get_block,
2947	struct writeback_control *wbc)
2948	{
2949	struct inode * const inode = page->mapping->host;
2950	loff_t i_size = i_size_read(inode);
2951	const pgoff_t end_index = i_size >> PAGE_SHIFT;
2952	unsigned offset;
2953
2954	/* Is the page fully inside i_size? */
2955	if (page->index < end_index)
2956	return __block_write_full_page(inode, page, get_block, wbc,
2957	end_buffer_async_write);
2958
2959	/* Is the page fully outside i_size? (truncate in progress) */
2960	offset = i_size & (PAGE_SIZE-1);
2961	if (page->index >= end_index+1 \|\| !offset) {
2962	unlock_page(page);
2963	return 0; /* don't care */
2964	}
2965
2966	/*
2967	* The page straddles i_size. It must be zeroed out on each and every
2968	* writepage invocation because it may be mmapped. "A file is mapped
2969	* in multiples of the page size. For a file that is not a multiple of
2970	* the page size, the remaining memory is zeroed when mapped, and
2971	* writes to that region are not written out to the file."
2972	*/
2973	zero_user_segment(page, offset, PAGE_SIZE);
2974	return __block_write_full_page(inode, page, get_block, wbc,
2975	end_buffer_async_write);
2976	}
2977	EXPORT_SYMBOL(block_write_full_page);
2978
2979	sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2980	get_block_t *get_block)
2981	{
2982	struct inode *inode = mapping->host;
2983	struct buffer_head tmp = {
2984	.b_size = i_blocksize(inode),
2985	};
2986
2987	get_block(inode, block, &tmp, 0);
2988	return tmp.b_blocknr;
2989	}
2990	EXPORT_SYMBOL(generic_block_bmap);
2991
2992	static void end_bio_bh_io_sync(struct bio *bio)
2993	{
2994	struct buffer_head *bh = bio->bi_private;
2995
2996	if (unlikely(bio_flagged(bio, BIO_QUIET)))
2997	set_bit(BH_Quiet, &bh->b_state);
2998
2999	bh->b_end_io(bh, !bio->bi_status);
3000	bio_put(bio);
3001	}
3002
3003	static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
3004	struct writeback_control *wbc)
3005	{
3006	struct bio *bio;
3007
3008	BUG_ON(!buffer_locked(bh));
3009	BUG_ON(!buffer_mapped(bh));
3010	BUG_ON(!bh->b_end_io);
3011	BUG_ON(buffer_delay(bh));
3012	BUG_ON(buffer_unwritten(bh));
3013
3014	/*
3015	* Only clear out a write error when rewriting
3016	*/
3017	if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
3018	clear_buffer_write_io_error(bh);
3019
3020	if (buffer_meta(bh))
3021	op_flags \|= REQ_META;
3022	if (buffer_prio(bh))
3023	op_flags \|= REQ_PRIO;
3024
3025	bio = bio_alloc(bh->b_bdev, 1, op \| op_flags, GFP_NOIO);
3026
3027	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
3028
3029	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3030
3031	bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
3032	BUG_ON(bio->bi_iter.bi_size != bh->b_size);
3033
3034	bio->bi_end_io = end_bio_bh_io_sync;
3035	bio->bi_private = bh;
3036
3037	/* Take care of bh's that straddle the end of the device */
3038	guard_bio_eod(bio);
3039
3040	if (wbc) {
3041	wbc_init_bio(wbc, bio);
3042	wbc_account_cgroup_owner(wbc, bh->b_page, bh->b_size);
3043	}
3044
3045	submit_bio(bio);
3046	return 0;
3047	}
3048
3049	int submit_bh(int op, int op_flags, struct buffer_head *bh)
3050	{
3051	return submit_bh_wbc(op, op_flags, bh, NULL);
3052	}
3053	EXPORT_SYMBOL(submit_bh);
3054
3055	/**
3056	* ll_rw_block: low-level access to block devices (DEPRECATED)
3057	* @op: whether to %READ or %WRITE
3058	* @op_flags: req_flag_bits
3059	* @nr: number of &struct buffer_heads in the array
3060	* @bhs: array of pointers to &struct buffer_head
3061	*
3062	* ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3063	* requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
3064	* @op_flags contains flags modifying the detailed I/O behavior, most notably
3065	* %REQ_RAHEAD.
3066	*
3067	* This function drops any buffer that it cannot get a lock on (with the
3068	* BH_Lock state bit), any buffer that appears to be clean when doing a write
3069	* request, and any buffer that appears to be up-to-date when doing read
3070	* request. Further it marks as clean buffers that are processed for
3071	* writing (the buffer cache won't assume that they are actually clean
3072	* until the buffer gets unlocked).
3073	*
3074	* ll_rw_block sets b_end_io to simple completion handler that marks
3075	* the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3076	* any waiters.
3077	*
3078	* All of the buffers must be for the same device, and must also be a
3079	* multiple of the current approved size for the device.
3080	*/
3081	void ll_rw_block(int op, int op_flags, int nr, struct buffer_head *bhs[])
3082	{
3083	int i;
3084
3085	for (i = 0; i < nr; i++) {
3086	struct buffer_head *bh = bhs[i];
3087
3088	if (!trylock_buffer(bh))
3089	continue;
3090	if (op == WRITE) {
3091	if (test_clear_buffer_dirty(bh)) {
3092	bh->b_end_io = end_buffer_write_sync;
3093	get_bh(bh);
3094	submit_bh(op, op_flags, bh);
3095	continue;
3096	}
3097	} else {
3098	if (!buffer_uptodate(bh)) {
3099	bh->b_end_io = end_buffer_read_sync;
3100	get_bh(bh);
3101	submit_bh(op, op_flags, bh);
3102	continue;
3103	}
3104	}
3105	unlock_buffer(bh);
3106	}
3107	}
3108	EXPORT_SYMBOL(ll_rw_block);
3109
3110	void write_dirty_buffer(struct buffer_head *bh, int op_flags)
3111	{
3112	lock_buffer(bh);
3113	if (!test_clear_buffer_dirty(bh)) {
3114	unlock_buffer(bh);
3115	return;
3116	}
3117	bh->b_end_io = end_buffer_write_sync;
3118	get_bh(bh);
3119	submit_bh(REQ_OP_WRITE, op_flags, bh);
3120	}
3121	EXPORT_SYMBOL(write_dirty_buffer);
3122
3123	/*
3124	* For a data-integrity writeout, we need to wait upon any in-progress I/O
3125	* and then start new I/O and then wait upon it. The caller must have a ref on
3126	* the buffer_head.
3127	*/
3128	int __sync_dirty_buffer(struct buffer_head *bh, int op_flags)
3129	{
3130	int ret = 0;
3131
3132	WARN_ON(atomic_read(&bh->b_count) < 1);
3133	lock_buffer(bh);
3134	if (test_clear_buffer_dirty(bh)) {
3135	/*
3136	* The bh should be mapped, but it might not be if the
3137	* device was hot-removed. Not much we can do but fail the I/O.
3138	*/
3139	if (!buffer_mapped(bh)) {
3140	unlock_buffer(bh);
3141	return -EIO;
3142	}
3143
3144	get_bh(bh);
3145	bh->b_end_io = end_buffer_write_sync;
3146	ret = submit_bh(REQ_OP_WRITE, op_flags, bh);
3147	wait_on_buffer(bh);
3148	if (!ret && !buffer_uptodate(bh))
3149	ret = -EIO;
3150	} else {
3151	unlock_buffer(bh);
3152	}
3153	return ret;
3154	}
3155	EXPORT_SYMBOL(__sync_dirty_buffer);
3156
3157	int sync_dirty_buffer(struct buffer_head *bh)
3158	{
3159	return __sync_dirty_buffer(bh, REQ_SYNC);
3160	}
3161	EXPORT_SYMBOL(sync_dirty_buffer);
3162
3163	/*
3164	* try_to_free_buffers() checks if all the buffers on this particular page
3165	* are unused, and releases them if so.
3166	*
3167	* Exclusion against try_to_free_buffers may be obtained by either
3168	* locking the page or by holding its mapping's private_lock.
3169	*
3170	* If the page is dirty but all the buffers are clean then we need to
3171	* be sure to mark the page clean as well. This is because the page
3172	* may be against a block device, and a later reattachment of buffers
3173	* to a dirty page will set all buffers dirty. Which would corrupt
3174	* filesystem data on the same device.
3175	*
3176	* The same applies to regular filesystem pages: if all the buffers are
3177	* clean then we set the page clean and proceed. To do that, we require
3178	* total exclusion from block_dirty_folio(). That is obtained with
3179	* private_lock.
3180	*
3181	* try_to_free_buffers() is non-blocking.
3182	*/
3183	static inline int buffer_busy(struct buffer_head *bh)
3184	{
3185	return atomic_read(&bh->b_count) \|
3186	(bh->b_state & ((1 << BH_Dirty) \| (1 << BH_Lock)));
3187	}
3188
3189	static int
3190	drop_buffers(struct page page, struct buffer_head *buffers_to_free)
3191	{
3192	struct buffer_head *head = page_buffers(page);
3193	struct buffer_head *bh;
3194
3195	bh = head;
3196	do {
3197	if (buffer_busy(bh))
3198	goto failed;
3199	bh = bh->b_this_page;
3200	} while (bh != head);
3201
3202	do {
3203	struct buffer_head *next = bh->b_this_page;
3204
3205	if (bh->b_assoc_map)
3206	__remove_assoc_queue(bh);
3207	bh = next;
3208	} while (bh != head);
3209	*buffers_to_free = head;
3210	detach_page_private(page);
3211	return 1;
3212	failed:
3213	return 0;
3214	}
3215
3216	int try_to_free_buffers(struct page *page)
3217	{
3218	struct address_space * const mapping = page->mapping;
3219	struct buffer_head *buffers_to_free = NULL;
3220	int ret = 0;
3221
3222	BUG_ON(!PageLocked(page));
3223	if (PageWriteback(page))
3224	return 0;
3225
3226	if (mapping == NULL) { /* can this still happen? */
3227	ret = drop_buffers(page, &buffers_to_free);
3228	goto out;
3229	}
3230
3231	spin_lock(&mapping->private_lock);
3232	ret = drop_buffers(page, &buffers_to_free);
3233
3234	/*
3235	* If the filesystem writes its buffers by hand (eg ext3)
3236	* then we can have clean buffers against a dirty page. We
3237	* clean the page here; otherwise the VM will never notice
3238	* that the filesystem did any IO at all.
3239	*
3240	* Also, during truncate, discard_buffer will have marked all
3241	* the page's buffers clean. We discover that here and clean
3242	* the page also.
3243	*
3244	* private_lock must be held over this entire operation in order
3245	* to synchronise against block_dirty_folio and prevent the
3246	* dirty bit from being lost.
3247	*/
3248	if (ret)
3249	cancel_dirty_page(page);
3250	spin_unlock(&mapping->private_lock);
3251	out:
3252	if (buffers_to_free) {
3253	struct buffer_head *bh = buffers_to_free;
3254
3255	do {
3256	struct buffer_head *next = bh->b_this_page;
3257	free_buffer_head(bh);
3258	bh = next;
3259	} while (bh != buffers_to_free);
3260	}
3261	return ret;
3262	}
3263	EXPORT_SYMBOL(try_to_free_buffers);
3264
3265	/*
3266	* Buffer-head allocation
3267	*/
3268	static struct kmem_cache *bh_cachep __read_mostly;
3269
3270	/*
3271	* Once the number of bh's in the machine exceeds this level, we start
3272	* stripping them in writeback.
3273	*/
3274	static unsigned long max_buffer_heads;
3275
3276	int buffer_heads_over_limit;
3277
3278	struct bh_accounting {
3279	int nr; /* Number of live bh's */
3280	int ratelimit; /* Limit cacheline bouncing */
3281	};
3282
3283	static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3284
3285	static void recalc_bh_state(void)
3286	{
3287	int i;
3288	int tot = 0;
3289
3290	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3291	return;
3292	__this_cpu_write(bh_accounting.ratelimit, 0);
3293	for_each_online_cpu(i)
3294	tot += per_cpu(bh_accounting, i).nr;
3295	buffer_heads_over_limit = (tot > max_buffer_heads);
3296	}
3297
3298	struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3299	{
3300	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3301	if (ret) {
3302	INIT_LIST_HEAD(&ret->b_assoc_buffers);
3303	spin_lock_init(&ret->b_uptodate_lock);
3304	preempt_disable();
3305	__this_cpu_inc(bh_accounting.nr);
3306	recalc_bh_state();
3307	preempt_enable();
3308	}
3309	return ret;
3310	}
3311	EXPORT_SYMBOL(alloc_buffer_head);
3312
3313	void free_buffer_head(struct buffer_head *bh)
3314	{
3315	BUG_ON(!list_empty(&bh->b_assoc_buffers));
3316	kmem_cache_free(bh_cachep, bh);
3317	preempt_disable();
3318	__this_cpu_dec(bh_accounting.nr);
3319	recalc_bh_state();
3320	preempt_enable();
3321	}
3322	EXPORT_SYMBOL(free_buffer_head);
3323
3324	static int buffer_exit_cpu_dead(unsigned int cpu)
3325	{
3326	int i;
3327	struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3328
3329	for (i = 0; i < BH_LRU_SIZE; i++) {
3330	brelse(b->bhs[i]);
3331	b->bhs[i] = NULL;
3332	}
3333	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3334	per_cpu(bh_accounting, cpu).nr = 0;
3335	return 0;
3336	}
3337
3338	/**
3339	* bh_uptodate_or_lock - Test whether the buffer is uptodate
3340	* @bh: struct buffer_head
3341	*
3342	* Return true if the buffer is up-to-date and false,
3343	* with the buffer locked, if not.
3344	*/
3345	int bh_uptodate_or_lock(struct buffer_head *bh)
3346	{
3347	if (!buffer_uptodate(bh)) {
3348	lock_buffer(bh);
3349	if (!buffer_uptodate(bh))
3350	return 0;
3351	unlock_buffer(bh);
3352	}
3353	return 1;
3354	}
3355	EXPORT_SYMBOL(bh_uptodate_or_lock);
3356
3357	/**
3358	* bh_submit_read - Submit a locked buffer for reading
3359	* @bh: struct buffer_head
3360	*
3361	* Returns zero on success and -EIO on error.
3362	*/
3363	int bh_submit_read(struct buffer_head *bh)
3364	{
3365	BUG_ON(!buffer_locked(bh));
3366
3367	if (buffer_uptodate(bh)) {
3368	unlock_buffer(bh);
3369	return 0;
3370	}
3371
3372	get_bh(bh);
3373	bh->b_end_io = end_buffer_read_sync;
3374	submit_bh(REQ_OP_READ, 0, bh);
3375	wait_on_buffer(bh);
3376	if (buffer_uptodate(bh))
3377	return 0;
3378	return -EIO;
3379	}
3380	EXPORT_SYMBOL(bh_submit_read);
3381
3382	void __init buffer_init(void)
3383	{
3384	unsigned long nrpages;
3385	int ret;
3386
3387	bh_cachep = kmem_cache_create("buffer_head",
3388	sizeof(struct buffer_head), 0,
3389	(SLAB_RECLAIM_ACCOUNT\|SLAB_PANIC\|
3390	SLAB_MEM_SPREAD),
3391	NULL);
3392
3393	/*
3394	* Limit the bh occupancy to 10% of ZONE_NORMAL
3395	*/
3396	nrpages = (nr_free_buffer_pages() * 10) / 100;
3397	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3398	ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3399	NULL, buffer_exit_cpu_dead);
3400	WARN_ON(ret < 0);
3401	}