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 <andrea@suse.de>
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 #include <linux/fsverity.h>
52 #include <linux/sched/isolation.h>
53 
54 #include "internal.h"
55 
56 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
57 static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
58 			  struct writeback_control *wbc);
59 
60 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
61 
touch_buffer(struct buffer_head * bh)62 inline void touch_buffer(struct buffer_head *bh)
63 {
64 	trace_block_touch_buffer(bh);
65 	folio_mark_accessed(bh->b_folio);
66 }
67 EXPORT_SYMBOL(touch_buffer);
68 
__lock_buffer(struct buffer_head * bh)69 void __lock_buffer(struct buffer_head *bh)
70 {
71 	wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
72 }
73 EXPORT_SYMBOL(__lock_buffer);
74 
unlock_buffer(struct buffer_head * bh)75 void unlock_buffer(struct buffer_head *bh)
76 {
77 	clear_bit_unlock(BH_Lock, &bh->b_state);
78 	smp_mb__after_atomic();
79 	wake_up_bit(&bh->b_state, BH_Lock);
80 }
81 EXPORT_SYMBOL(unlock_buffer);
82 
83 /*
84  * Returns if the folio has dirty or writeback buffers. If all the buffers
85  * are unlocked and clean then the folio_test_dirty information is stale. If
86  * any of the buffers are locked, it is assumed they are locked for IO.
87  */
buffer_check_dirty_writeback(struct folio * folio,bool * dirty,bool * writeback)88 void buffer_check_dirty_writeback(struct folio *folio,
89 				     bool *dirty, bool *writeback)
90 {
91 	struct buffer_head *head, *bh;
92 	*dirty = false;
93 	*writeback = false;
94 
95 	BUG_ON(!folio_test_locked(folio));
96 
97 	head = folio_buffers(folio);
98 	if (!head)
99 		return;
100 
101 	if (folio_test_writeback(folio))
102 		*writeback = true;
103 
104 	bh = head;
105 	do {
106 		if (buffer_locked(bh))
107 			*writeback = true;
108 
109 		if (buffer_dirty(bh))
110 			*dirty = true;
111 
112 		bh = bh->b_this_page;
113 	} while (bh != head);
114 }
115 
116 /*
117  * Block until a buffer comes unlocked.  This doesn't stop it
118  * from becoming locked again - you have to lock it yourself
119  * if you want to preserve its state.
120  */
__wait_on_buffer(struct buffer_head * bh)121 void __wait_on_buffer(struct buffer_head * bh)
122 {
123 	wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
124 }
125 EXPORT_SYMBOL(__wait_on_buffer);
126 
buffer_io_error(struct buffer_head * bh,char * msg)127 static void buffer_io_error(struct buffer_head *bh, char *msg)
128 {
129 	if (!test_bit(BH_Quiet, &bh->b_state))
130 		printk_ratelimited(KERN_ERR
131 			"Buffer I/O error on dev %pg, logical block %llu%s\n",
132 			bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
133 }
134 
135 /*
136  * End-of-IO handler helper function which does not touch the bh after
137  * unlocking it.
138  * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
139  * a race there is benign: unlock_buffer() only use the bh's address for
140  * hashing after unlocking the buffer, so it doesn't actually touch the bh
141  * itself.
142  */
__end_buffer_read_notouch(struct buffer_head * bh,int uptodate)143 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
144 {
145 	if (uptodate) {
146 		set_buffer_uptodate(bh);
147 	} else {
148 		/* This happens, due to failed read-ahead attempts. */
149 		clear_buffer_uptodate(bh);
150 	}
151 	unlock_buffer(bh);
152 }
153 
154 /*
155  * Default synchronous end-of-IO handler..  Just mark it up-to-date and
156  * unlock the buffer.
157  */
end_buffer_read_sync(struct buffer_head * bh,int uptodate)158 void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
159 {
160 	__end_buffer_read_notouch(bh, uptodate);
161 	put_bh(bh);
162 }
163 EXPORT_SYMBOL(end_buffer_read_sync);
164 
end_buffer_write_sync(struct buffer_head * bh,int uptodate)165 void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
166 {
167 	if (uptodate) {
168 		set_buffer_uptodate(bh);
169 	} else {
170 		buffer_io_error(bh, ", lost sync page write");
171 		mark_buffer_write_io_error(bh);
172 		clear_buffer_uptodate(bh);
173 	}
174 	unlock_buffer(bh);
175 	put_bh(bh);
176 }
177 EXPORT_SYMBOL(end_buffer_write_sync);
178 
179 /*
180  * Various filesystems appear to want __find_get_block to be non-blocking.
181  * But it's the page lock which protects the buffers.  To get around this,
182  * we get exclusion from try_to_free_buffers with the blockdev mapping's
183  * private_lock.
184  *
185  * Hack idea: for the blockdev mapping, private_lock contention
186  * may be quite high.  This code could TryLock the page, and if that
187  * succeeds, there is no need to take private_lock.
188  */
189 static struct buffer_head *
__find_get_block_slow(struct block_device * bdev,sector_t block)190 __find_get_block_slow(struct block_device *bdev, sector_t block)
191 {
192 	struct inode *bd_inode = bdev->bd_inode;
193 	struct address_space *bd_mapping = bd_inode->i_mapping;
194 	struct buffer_head *ret = NULL;
195 	pgoff_t index;
196 	struct buffer_head *bh;
197 	struct buffer_head *head;
198 	struct folio *folio;
199 	int all_mapped = 1;
200 	static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
201 
202 	index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
203 	folio = __filemap_get_folio(bd_mapping, index, FGP_ACCESSED, 0);
204 	if (IS_ERR(folio))
205 		goto out;
206 
207 	spin_lock(&bd_mapping->private_lock);
208 	head = folio_buffers(folio);
209 	if (!head)
210 		goto out_unlock;
211 	bh = head;
212 	do {
213 		if (!buffer_mapped(bh))
214 			all_mapped = 0;
215 		else if (bh->b_blocknr == block) {
216 			ret = bh;
217 			get_bh(bh);
218 			goto out_unlock;
219 		}
220 		bh = bh->b_this_page;
221 	} while (bh != head);
222 
223 	/* we might be here because some of the buffers on this page are
224 	 * not mapped.  This is due to various races between
225 	 * file io on the block device and getblk.  It gets dealt with
226 	 * elsewhere, don't buffer_error if we had some unmapped buffers
227 	 */
228 	ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
229 	if (all_mapped && __ratelimit(&last_warned)) {
230 		printk("__find_get_block_slow() failed. block=%llu, "
231 		       "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
232 		       "device %pg blocksize: %d\n",
233 		       (unsigned long long)block,
234 		       (unsigned long long)bh->b_blocknr,
235 		       bh->b_state, bh->b_size, bdev,
236 		       1 << bd_inode->i_blkbits);
237 	}
238 out_unlock:
239 	spin_unlock(&bd_mapping->private_lock);
240 	folio_put(folio);
241 out:
242 	return ret;
243 }
244 
end_buffer_async_read(struct buffer_head * bh,int uptodate)245 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
246 {
247 	unsigned long flags;
248 	struct buffer_head *first;
249 	struct buffer_head *tmp;
250 	struct folio *folio;
251 	int folio_uptodate = 1;
252 
253 	BUG_ON(!buffer_async_read(bh));
254 
255 	folio = bh->b_folio;
256 	if (uptodate) {
257 		set_buffer_uptodate(bh);
258 	} else {
259 		clear_buffer_uptodate(bh);
260 		buffer_io_error(bh, ", async page read");
261 		folio_set_error(folio);
262 	}
263 
264 	/*
265 	 * Be _very_ careful from here on. Bad things can happen if
266 	 * two buffer heads end IO at almost the same time and both
267 	 * decide that the page is now completely done.
268 	 */
269 	first = folio_buffers(folio);
270 	spin_lock_irqsave(&first->b_uptodate_lock, flags);
271 	clear_buffer_async_read(bh);
272 	unlock_buffer(bh);
273 	tmp = bh;
274 	do {
275 		if (!buffer_uptodate(tmp))
276 			folio_uptodate = 0;
277 		if (buffer_async_read(tmp)) {
278 			BUG_ON(!buffer_locked(tmp));
279 			goto still_busy;
280 		}
281 		tmp = tmp->b_this_page;
282 	} while (tmp != bh);
283 	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
284 
285 	/*
286 	 * If all of the buffers are uptodate then we can set the page
287 	 * uptodate.
288 	 */
289 	if (folio_uptodate)
290 		folio_mark_uptodate(folio);
291 	folio_unlock(folio);
292 	return;
293 
294 still_busy:
295 	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
296 	return;
297 }
298 
299 struct postprocess_bh_ctx {
300 	struct work_struct work;
301 	struct buffer_head *bh;
302 };
303 
verify_bh(struct work_struct * work)304 static void verify_bh(struct work_struct *work)
305 {
306 	struct postprocess_bh_ctx *ctx =
307 		container_of(work, struct postprocess_bh_ctx, work);
308 	struct buffer_head *bh = ctx->bh;
309 	bool valid;
310 
311 	valid = fsverity_verify_blocks(bh->b_folio, bh->b_size, bh_offset(bh));
312 	end_buffer_async_read(bh, valid);
313 	kfree(ctx);
314 }
315 
need_fsverity(struct buffer_head * bh)316 static bool need_fsverity(struct buffer_head *bh)
317 {
318 	struct folio *folio = bh->b_folio;
319 	struct inode *inode = folio->mapping->host;
320 
321 	return fsverity_active(inode) &&
322 		/* needed by ext4 */
323 		folio->index < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
324 }
325 
decrypt_bh(struct work_struct * work)326 static void decrypt_bh(struct work_struct *work)
327 {
328 	struct postprocess_bh_ctx *ctx =
329 		container_of(work, struct postprocess_bh_ctx, work);
330 	struct buffer_head *bh = ctx->bh;
331 	int err;
332 
333 	err = fscrypt_decrypt_pagecache_blocks(bh->b_folio, bh->b_size,
334 					       bh_offset(bh));
335 	if (err == 0 && need_fsverity(bh)) {
336 		/*
337 		 * We use different work queues for decryption and for verity
338 		 * because verity may require reading metadata pages that need
339 		 * decryption, and we shouldn't recurse to the same workqueue.
340 		 */
341 		INIT_WORK(&ctx->work, verify_bh);
342 		fsverity_enqueue_verify_work(&ctx->work);
343 		return;
344 	}
345 	end_buffer_async_read(bh, err == 0);
346 	kfree(ctx);
347 }
348 
349 /*
350  * I/O completion handler for block_read_full_folio() - pages
351  * which come unlocked at the end of I/O.
352  */
end_buffer_async_read_io(struct buffer_head * bh,int uptodate)353 static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
354 {
355 	struct inode *inode = bh->b_folio->mapping->host;
356 	bool decrypt = fscrypt_inode_uses_fs_layer_crypto(inode);
357 	bool verify = need_fsverity(bh);
358 
359 	/* Decrypt (with fscrypt) and/or verify (with fsverity) if needed. */
360 	if (uptodate && (decrypt || verify)) {
361 		struct postprocess_bh_ctx *ctx =
362 			kmalloc(sizeof(*ctx), GFP_ATOMIC);
363 
364 		if (ctx) {
365 			ctx->bh = bh;
366 			if (decrypt) {
367 				INIT_WORK(&ctx->work, decrypt_bh);
368 				fscrypt_enqueue_decrypt_work(&ctx->work);
369 			} else {
370 				INIT_WORK(&ctx->work, verify_bh);
371 				fsverity_enqueue_verify_work(&ctx->work);
372 			}
373 			return;
374 		}
375 		uptodate = 0;
376 	}
377 	end_buffer_async_read(bh, uptodate);
378 }
379 
380 /*
381  * Completion handler for block_write_full_page() - pages which are unlocked
382  * during I/O, and which have PageWriteback cleared upon I/O completion.
383  */
end_buffer_async_write(struct buffer_head * bh,int uptodate)384 void end_buffer_async_write(struct buffer_head *bh, int uptodate)
385 {
386 	unsigned long flags;
387 	struct buffer_head *first;
388 	struct buffer_head *tmp;
389 	struct folio *folio;
390 
391 	BUG_ON(!buffer_async_write(bh));
392 
393 	folio = bh->b_folio;
394 	if (uptodate) {
395 		set_buffer_uptodate(bh);
396 	} else {
397 		buffer_io_error(bh, ", lost async page write");
398 		mark_buffer_write_io_error(bh);
399 		clear_buffer_uptodate(bh);
400 		folio_set_error(folio);
401 	}
402 
403 	first = folio_buffers(folio);
404 	spin_lock_irqsave(&first->b_uptodate_lock, flags);
405 
406 	clear_buffer_async_write(bh);
407 	unlock_buffer(bh);
408 	tmp = bh->b_this_page;
409 	while (tmp != bh) {
410 		if (buffer_async_write(tmp)) {
411 			BUG_ON(!buffer_locked(tmp));
412 			goto still_busy;
413 		}
414 		tmp = tmp->b_this_page;
415 	}
416 	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
417 	folio_end_writeback(folio);
418 	return;
419 
420 still_busy:
421 	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
422 	return;
423 }
424 EXPORT_SYMBOL(end_buffer_async_write);
425 
426 /*
427  * If a page's buffers are under async readin (end_buffer_async_read
428  * completion) then there is a possibility that another thread of
429  * control could lock one of the buffers after it has completed
430  * but while some of the other buffers have not completed.  This
431  * locked buffer would confuse end_buffer_async_read() into not unlocking
432  * the page.  So the absence of BH_Async_Read tells end_buffer_async_read()
433  * that this buffer is not under async I/O.
434  *
435  * The page comes unlocked when it has no locked buffer_async buffers
436  * left.
437  *
438  * PageLocked prevents anyone starting new async I/O reads any of
439  * the buffers.
440  *
441  * PageWriteback is used to prevent simultaneous writeout of the same
442  * page.
443  *
444  * PageLocked prevents anyone from starting writeback of a page which is
445  * under read I/O (PageWriteback is only ever set against a locked page).
446  */
mark_buffer_async_read(struct buffer_head * bh)447 static void mark_buffer_async_read(struct buffer_head *bh)
448 {
449 	bh->b_end_io = end_buffer_async_read_io;
450 	set_buffer_async_read(bh);
451 }
452 
mark_buffer_async_write_endio(struct buffer_head * bh,bh_end_io_t * handler)453 static void mark_buffer_async_write_endio(struct buffer_head *bh,
454 					  bh_end_io_t *handler)
455 {
456 	bh->b_end_io = handler;
457 	set_buffer_async_write(bh);
458 }
459 
mark_buffer_async_write(struct buffer_head * bh)460 void mark_buffer_async_write(struct buffer_head *bh)
461 {
462 	mark_buffer_async_write_endio(bh, end_buffer_async_write);
463 }
464 EXPORT_SYMBOL(mark_buffer_async_write);
465 
466 
467 /*
468  * fs/buffer.c contains helper functions for buffer-backed address space's
469  * fsync functions.  A common requirement for buffer-based filesystems is
470  * that certain data from the backing blockdev needs to be written out for
471  * a successful fsync().  For example, ext2 indirect blocks need to be
472  * written back and waited upon before fsync() returns.
473  *
474  * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
475  * inode_has_buffers() and invalidate_inode_buffers() are provided for the
476  * management of a list of dependent buffers at ->i_mapping->private_list.
477  *
478  * Locking is a little subtle: try_to_free_buffers() will remove buffers
479  * from their controlling inode's queue when they are being freed.  But
480  * try_to_free_buffers() will be operating against the *blockdev* mapping
481  * at the time, not against the S_ISREG file which depends on those buffers.
482  * So the locking for private_list is via the private_lock in the address_space
483  * which backs the buffers.  Which is different from the address_space
484  * against which the buffers are listed.  So for a particular address_space,
485  * mapping->private_lock does *not* protect mapping->private_list!  In fact,
486  * mapping->private_list will always be protected by the backing blockdev's
487  * ->private_lock.
488  *
489  * Which introduces a requirement: all buffers on an address_space's
490  * ->private_list must be from the same address_space: the blockdev's.
491  *
492  * address_spaces which do not place buffers at ->private_list via these
493  * utility functions are free to use private_lock and private_list for
494  * whatever they want.  The only requirement is that list_empty(private_list)
495  * be true at clear_inode() time.
496  *
497  * FIXME: clear_inode should not call invalidate_inode_buffers().  The
498  * filesystems should do that.  invalidate_inode_buffers() should just go
499  * BUG_ON(!list_empty).
500  *
501  * FIXME: mark_buffer_dirty_inode() is a data-plane operation.  It should
502  * take an address_space, not an inode.  And it should be called
503  * mark_buffer_dirty_fsync() to clearly define why those buffers are being
504  * queued up.
505  *
506  * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
507  * list if it is already on a list.  Because if the buffer is on a list,
508  * it *must* already be on the right one.  If not, the filesystem is being
509  * silly.  This will save a ton of locking.  But first we have to ensure
510  * that buffers are taken *off* the old inode's list when they are freed
511  * (presumably in truncate).  That requires careful auditing of all
512  * filesystems (do it inside bforget()).  It could also be done by bringing
513  * b_inode back.
514  */
515 
516 /*
517  * The buffer's backing address_space's private_lock must be held
518  */
__remove_assoc_queue(struct buffer_head * bh)519 static void __remove_assoc_queue(struct buffer_head *bh)
520 {
521 	list_del_init(&bh->b_assoc_buffers);
522 	WARN_ON(!bh->b_assoc_map);
523 	bh->b_assoc_map = NULL;
524 }
525 
inode_has_buffers(struct inode * inode)526 int inode_has_buffers(struct inode *inode)
527 {
528 	return !list_empty(&inode->i_data.private_list);
529 }
530 
531 /*
532  * osync is designed to support O_SYNC io.  It waits synchronously for
533  * all already-submitted IO to complete, but does not queue any new
534  * writes to the disk.
535  *
536  * To do O_SYNC writes, just queue the buffer writes with write_dirty_buffer
537  * as you dirty the buffers, and then use osync_inode_buffers to wait for
538  * completion.  Any other dirty buffers which are not yet queued for
539  * write will not be flushed to disk by the osync.
540  */
osync_buffers_list(spinlock_t * lock,struct list_head * list)541 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
542 {
543 	struct buffer_head *bh;
544 	struct list_head *p;
545 	int err = 0;
546 
547 	spin_lock(lock);
548 repeat:
549 	list_for_each_prev(p, list) {
550 		bh = BH_ENTRY(p);
551 		if (buffer_locked(bh)) {
552 			get_bh(bh);
553 			spin_unlock(lock);
554 			wait_on_buffer(bh);
555 			if (!buffer_uptodate(bh))
556 				err = -EIO;
557 			brelse(bh);
558 			spin_lock(lock);
559 			goto repeat;
560 		}
561 	}
562 	spin_unlock(lock);
563 	return err;
564 }
565 
566 /**
567  * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
568  * @mapping: the mapping which wants those buffers written
569  *
570  * Starts I/O against the buffers at mapping->private_list, and waits upon
571  * that I/O.
572  *
573  * Basically, this is a convenience function for fsync().
574  * @mapping is a file or directory which needs those buffers to be written for
575  * a successful fsync().
576  */
sync_mapping_buffers(struct address_space * mapping)577 int sync_mapping_buffers(struct address_space *mapping)
578 {
579 	struct address_space *buffer_mapping = mapping->private_data;
580 
581 	if (buffer_mapping == NULL || list_empty(&mapping->private_list))
582 		return 0;
583 
584 	return fsync_buffers_list(&buffer_mapping->private_lock,
585 					&mapping->private_list);
586 }
587 EXPORT_SYMBOL(sync_mapping_buffers);
588 
589 /**
590  * generic_buffers_fsync_noflush - generic buffer fsync implementation
591  * for simple filesystems with no inode lock
592  *
593  * @file:	file to synchronize
594  * @start:	start offset in bytes
595  * @end:	end offset in bytes (inclusive)
596  * @datasync:	only synchronize essential metadata if true
597  *
598  * This is a generic implementation of the fsync method for simple
599  * filesystems which track all non-inode metadata in the buffers list
600  * hanging off the address_space structure.
601  */
generic_buffers_fsync_noflush(struct file * file,loff_t start,loff_t end,bool datasync)602 int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end,
603 				  bool datasync)
604 {
605 	struct inode *inode = file->f_mapping->host;
606 	int err;
607 	int ret;
608 
609 	err = file_write_and_wait_range(file, start, end);
610 	if (err)
611 		return err;
612 
613 	ret = sync_mapping_buffers(inode->i_mapping);
614 	if (!(inode->i_state & I_DIRTY_ALL))
615 		goto out;
616 	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
617 		goto out;
618 
619 	err = sync_inode_metadata(inode, 1);
620 	if (ret == 0)
621 		ret = err;
622 
623 out:
624 	/* check and advance again to catch errors after syncing out buffers */
625 	err = file_check_and_advance_wb_err(file);
626 	if (ret == 0)
627 		ret = err;
628 	return ret;
629 }
630 EXPORT_SYMBOL(generic_buffers_fsync_noflush);
631 
632 /**
633  * generic_buffers_fsync - generic buffer fsync implementation
634  * for simple filesystems with no inode lock
635  *
636  * @file:	file to synchronize
637  * @start:	start offset in bytes
638  * @end:	end offset in bytes (inclusive)
639  * @datasync:	only synchronize essential metadata if true
640  *
641  * This is a generic implementation of the fsync method for simple
642  * filesystems which track all non-inode metadata in the buffers list
643  * hanging off the address_space structure. This also makes sure that
644  * a device cache flush operation is called at the end.
645  */
generic_buffers_fsync(struct file * file,loff_t start,loff_t end,bool datasync)646 int generic_buffers_fsync(struct file *file, loff_t start, loff_t end,
647 			  bool datasync)
648 {
649 	struct inode *inode = file->f_mapping->host;
650 	int ret;
651 
652 	ret = generic_buffers_fsync_noflush(file, start, end, datasync);
653 	if (!ret)
654 		ret = blkdev_issue_flush(inode->i_sb->s_bdev);
655 	return ret;
656 }
657 EXPORT_SYMBOL(generic_buffers_fsync);
658 
659 /*
660  * Called when we've recently written block `bblock', and it is known that
661  * `bblock' was for a buffer_boundary() buffer.  This means that the block at
662  * `bblock + 1' is probably a dirty indirect block.  Hunt it down and, if it's
663  * dirty, schedule it for IO.  So that indirects merge nicely with their data.
664  */
write_boundary_block(struct block_device * bdev,sector_t bblock,unsigned blocksize)665 void write_boundary_block(struct block_device *bdev,
666 			sector_t bblock, unsigned blocksize)
667 {
668 	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
669 	if (bh) {
670 		if (buffer_dirty(bh))
671 			write_dirty_buffer(bh, 0);
672 		put_bh(bh);
673 	}
674 }
675 
mark_buffer_dirty_inode(struct buffer_head * bh,struct inode * inode)676 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
677 {
678 	struct address_space *mapping = inode->i_mapping;
679 	struct address_space *buffer_mapping = bh->b_folio->mapping;
680 
681 	mark_buffer_dirty(bh);
682 	if (!mapping->private_data) {
683 		mapping->private_data = buffer_mapping;
684 	} else {
685 		BUG_ON(mapping->private_data != buffer_mapping);
686 	}
687 	if (!bh->b_assoc_map) {
688 		spin_lock(&buffer_mapping->private_lock);
689 		list_move_tail(&bh->b_assoc_buffers,
690 				&mapping->private_list);
691 		bh->b_assoc_map = mapping;
692 		spin_unlock(&buffer_mapping->private_lock);
693 	}
694 }
695 EXPORT_SYMBOL(mark_buffer_dirty_inode);
696 
697 /*
698  * Add a page to the dirty page list.
699  *
700  * It is a sad fact of life that this function is called from several places
701  * deeply under spinlocking.  It may not sleep.
702  *
703  * If the page has buffers, the uptodate buffers are set dirty, to preserve
704  * dirty-state coherency between the page and the buffers.  It the page does
705  * not have buffers then when they are later attached they will all be set
706  * dirty.
707  *
708  * The buffers are dirtied before the page is dirtied.  There's a small race
709  * window in which a writepage caller may see the page cleanness but not the
710  * buffer dirtiness.  That's fine.  If this code were to set the page dirty
711  * before the buffers, a concurrent writepage caller could clear the page dirty
712  * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
713  * page on the dirty page list.
714  *
715  * We use private_lock to lock against try_to_free_buffers while using the
716  * page's buffer list.  Also use this to protect against clean buffers being
717  * added to the page after it was set dirty.
718  *
719  * FIXME: may need to call ->reservepage here as well.  That's rather up to the
720  * address_space though.
721  */
block_dirty_folio(struct address_space * mapping,struct folio * folio)722 bool block_dirty_folio(struct address_space *mapping, struct folio *folio)
723 {
724 	struct buffer_head *head;
725 	bool newly_dirty;
726 
727 	spin_lock(&mapping->private_lock);
728 	head = folio_buffers(folio);
729 	if (head) {
730 		struct buffer_head *bh = head;
731 
732 		do {
733 			set_buffer_dirty(bh);
734 			bh = bh->b_this_page;
735 		} while (bh != head);
736 	}
737 	/*
738 	 * Lock out page's memcg migration to keep PageDirty
739 	 * synchronized with per-memcg dirty page counters.
740 	 */
741 	folio_memcg_lock(folio);
742 	newly_dirty = !folio_test_set_dirty(folio);
743 	spin_unlock(&mapping->private_lock);
744 
745 	if (newly_dirty)
746 		__folio_mark_dirty(folio, mapping, 1);
747 
748 	folio_memcg_unlock(folio);
749 
750 	if (newly_dirty)
751 		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
752 
753 	return newly_dirty;
754 }
755 EXPORT_SYMBOL(block_dirty_folio);
756 
757 /*
758  * Write out and wait upon a list of buffers.
759  *
760  * We have conflicting pressures: we want to make sure that all
761  * initially dirty buffers get waited on, but that any subsequently
762  * dirtied buffers don't.  After all, we don't want fsync to last
763  * forever if somebody is actively writing to the file.
764  *
765  * Do this in two main stages: first we copy dirty buffers to a
766  * temporary inode list, queueing the writes as we go.  Then we clean
767  * up, waiting for those writes to complete.
768  *
769  * During this second stage, any subsequent updates to the file may end
770  * up refiling the buffer on the original inode's dirty list again, so
771  * there is a chance we will end up with a buffer queued for write but
772  * not yet completed on that list.  So, as a final cleanup we go through
773  * the osync code to catch these locked, dirty buffers without requeuing
774  * any newly dirty buffers for write.
775  */
fsync_buffers_list(spinlock_t * lock,struct list_head * list)776 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
777 {
778 	struct buffer_head *bh;
779 	struct list_head tmp;
780 	struct address_space *mapping;
781 	int err = 0, err2;
782 	struct blk_plug plug;
783 
784 	INIT_LIST_HEAD(&tmp);
785 	blk_start_plug(&plug);
786 
787 	spin_lock(lock);
788 	while (!list_empty(list)) {
789 		bh = BH_ENTRY(list->next);
790 		mapping = bh->b_assoc_map;
791 		__remove_assoc_queue(bh);
792 		/* Avoid race with mark_buffer_dirty_inode() which does
793 		 * a lockless check and we rely on seeing the dirty bit */
794 		smp_mb();
795 		if (buffer_dirty(bh) || buffer_locked(bh)) {
796 			list_add(&bh->b_assoc_buffers, &tmp);
797 			bh->b_assoc_map = mapping;
798 			if (buffer_dirty(bh)) {
799 				get_bh(bh);
800 				spin_unlock(lock);
801 				/*
802 				 * Ensure any pending I/O completes so that
803 				 * write_dirty_buffer() actually writes the
804 				 * current contents - it is a noop if I/O is
805 				 * still in flight on potentially older
806 				 * contents.
807 				 */
808 				write_dirty_buffer(bh, REQ_SYNC);
809 
810 				/*
811 				 * Kick off IO for the previous mapping. Note
812 				 * that we will not run the very last mapping,
813 				 * wait_on_buffer() will do that for us
814 				 * through sync_buffer().
815 				 */
816 				brelse(bh);
817 				spin_lock(lock);
818 			}
819 		}
820 	}
821 
822 	spin_unlock(lock);
823 	blk_finish_plug(&plug);
824 	spin_lock(lock);
825 
826 	while (!list_empty(&tmp)) {
827 		bh = BH_ENTRY(tmp.prev);
828 		get_bh(bh);
829 		mapping = bh->b_assoc_map;
830 		__remove_assoc_queue(bh);
831 		/* Avoid race with mark_buffer_dirty_inode() which does
832 		 * a lockless check and we rely on seeing the dirty bit */
833 		smp_mb();
834 		if (buffer_dirty(bh)) {
835 			list_add(&bh->b_assoc_buffers,
836 				 &mapping->private_list);
837 			bh->b_assoc_map = mapping;
838 		}
839 		spin_unlock(lock);
840 		wait_on_buffer(bh);
841 		if (!buffer_uptodate(bh))
842 			err = -EIO;
843 		brelse(bh);
844 		spin_lock(lock);
845 	}
846 
847 	spin_unlock(lock);
848 	err2 = osync_buffers_list(lock, list);
849 	if (err)
850 		return err;
851 	else
852 		return err2;
853 }
854 
855 /*
856  * Invalidate any and all dirty buffers on a given inode.  We are
857  * probably unmounting the fs, but that doesn't mean we have already
858  * done a sync().  Just drop the buffers from the inode list.
859  *
860  * NOTE: we take the inode's blockdev's mapping's private_lock.  Which
861  * assumes that all the buffers are against the blockdev.  Not true
862  * for reiserfs.
863  */
invalidate_inode_buffers(struct inode * inode)864 void invalidate_inode_buffers(struct inode *inode)
865 {
866 	if (inode_has_buffers(inode)) {
867 		struct address_space *mapping = &inode->i_data;
868 		struct list_head *list = &mapping->private_list;
869 		struct address_space *buffer_mapping = mapping->private_data;
870 
871 		spin_lock(&buffer_mapping->private_lock);
872 		while (!list_empty(list))
873 			__remove_assoc_queue(BH_ENTRY(list->next));
874 		spin_unlock(&buffer_mapping->private_lock);
875 	}
876 }
877 EXPORT_SYMBOL(invalidate_inode_buffers);
878 
879 /*
880  * Remove any clean buffers from the inode's buffer list.  This is called
881  * when we're trying to free the inode itself.  Those buffers can pin it.
882  *
883  * Returns true if all buffers were removed.
884  */
remove_inode_buffers(struct inode * inode)885 int remove_inode_buffers(struct inode *inode)
886 {
887 	int ret = 1;
888 
889 	if (inode_has_buffers(inode)) {
890 		struct address_space *mapping = &inode->i_data;
891 		struct list_head *list = &mapping->private_list;
892 		struct address_space *buffer_mapping = mapping->private_data;
893 
894 		spin_lock(&buffer_mapping->private_lock);
895 		while (!list_empty(list)) {
896 			struct buffer_head *bh = BH_ENTRY(list->next);
897 			if (buffer_dirty(bh)) {
898 				ret = 0;
899 				break;
900 			}
901 			__remove_assoc_queue(bh);
902 		}
903 		spin_unlock(&buffer_mapping->private_lock);
904 	}
905 	return ret;
906 }
907 
908 /*
909  * Create the appropriate buffers when given a folio for data area and
910  * the size of each buffer.. Use the bh->b_this_page linked list to
911  * follow the buffers created.  Return NULL if unable to create more
912  * buffers.
913  *
914  * The retry flag is used to differentiate async IO (paging, swapping)
915  * which may not fail from ordinary buffer allocations.
916  */
folio_alloc_buffers(struct folio * folio,unsigned long size,bool retry)917 struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size,
918 					bool retry)
919 {
920 	struct buffer_head *bh, *head;
921 	gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
922 	long offset;
923 	struct mem_cgroup *memcg, *old_memcg;
924 
925 	if (retry)
926 		gfp |= __GFP_NOFAIL;
927 
928 	/* The folio lock pins the memcg */
929 	memcg = folio_memcg(folio);
930 	old_memcg = set_active_memcg(memcg);
931 
932 	head = NULL;
933 	offset = folio_size(folio);
934 	while ((offset -= size) >= 0) {
935 		bh = alloc_buffer_head(gfp);
936 		if (!bh)
937 			goto no_grow;
938 
939 		bh->b_this_page = head;
940 		bh->b_blocknr = -1;
941 		head = bh;
942 
943 		bh->b_size = size;
944 
945 		/* Link the buffer to its folio */
946 		folio_set_bh(bh, folio, offset);
947 	}
948 out:
949 	set_active_memcg(old_memcg);
950 	return head;
951 /*
952  * In case anything failed, we just free everything we got.
953  */
954 no_grow:
955 	if (head) {
956 		do {
957 			bh = head;
958 			head = head->b_this_page;
959 			free_buffer_head(bh);
960 		} while (head);
961 	}
962 
963 	goto out;
964 }
965 EXPORT_SYMBOL_GPL(folio_alloc_buffers);
966 
alloc_page_buffers(struct page * page,unsigned long size,bool retry)967 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
968 				       bool retry)
969 {
970 	return folio_alloc_buffers(page_folio(page), size, retry);
971 }
972 EXPORT_SYMBOL_GPL(alloc_page_buffers);
973 
link_dev_buffers(struct folio * folio,struct buffer_head * head)974 static inline void link_dev_buffers(struct folio *folio,
975 		struct buffer_head *head)
976 {
977 	struct buffer_head *bh, *tail;
978 
979 	bh = head;
980 	do {
981 		tail = bh;
982 		bh = bh->b_this_page;
983 	} while (bh);
984 	tail->b_this_page = head;
985 	folio_attach_private(folio, head);
986 }
987 
blkdev_max_block(struct block_device * bdev,unsigned int size)988 static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
989 {
990 	sector_t retval = ~((sector_t)0);
991 	loff_t sz = bdev_nr_bytes(bdev);
992 
993 	if (sz) {
994 		unsigned int sizebits = blksize_bits(size);
995 		retval = (sz >> sizebits);
996 	}
997 	return retval;
998 }
999 
1000 /*
1001  * Initialise the state of a blockdev folio's buffers.
1002  */
folio_init_buffers(struct folio * folio,struct block_device * bdev,sector_t block,int size)1003 static sector_t folio_init_buffers(struct folio *folio,
1004 		struct block_device *bdev, sector_t block, int size)
1005 {
1006 	struct buffer_head *head = folio_buffers(folio);
1007 	struct buffer_head *bh = head;
1008 	bool uptodate = folio_test_uptodate(folio);
1009 	sector_t end_block = blkdev_max_block(bdev, size);
1010 
1011 	do {
1012 		if (!buffer_mapped(bh)) {
1013 			bh->b_end_io = NULL;
1014 			bh->b_private = NULL;
1015 			bh->b_bdev = bdev;
1016 			bh->b_blocknr = block;
1017 			if (uptodate)
1018 				set_buffer_uptodate(bh);
1019 			if (block < end_block)
1020 				set_buffer_mapped(bh);
1021 		}
1022 		block++;
1023 		bh = bh->b_this_page;
1024 	} while (bh != head);
1025 
1026 	/*
1027 	 * Caller needs to validate requested block against end of device.
1028 	 */
1029 	return end_block;
1030 }
1031 
1032 /*
1033  * Create the page-cache page that contains the requested block.
1034  *
1035  * This is used purely for blockdev mappings.
1036  */
1037 static int
grow_dev_page(struct block_device * bdev,sector_t block,pgoff_t index,int size,int sizebits,gfp_t gfp)1038 grow_dev_page(struct block_device *bdev, sector_t block,
1039 	      pgoff_t index, int size, int sizebits, gfp_t gfp)
1040 {
1041 	struct inode *inode = bdev->bd_inode;
1042 	struct folio *folio;
1043 	struct buffer_head *bh;
1044 	sector_t end_block;
1045 	int ret = 0;
1046 	gfp_t gfp_mask;
1047 
1048 	gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
1049 
1050 	/*
1051 	 * XXX: __getblk_slow() can not really deal with failure and
1052 	 * will endlessly loop on improvised global reclaim.  Prefer
1053 	 * looping in the allocator rather than here, at least that
1054 	 * code knows what it's doing.
1055 	 */
1056 	gfp_mask |= __GFP_NOFAIL;
1057 
1058 	folio = __filemap_get_folio(inode->i_mapping, index,
1059 			FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp_mask);
1060 
1061 	bh = folio_buffers(folio);
1062 	if (bh) {
1063 		if (bh->b_size == size) {
1064 			end_block = folio_init_buffers(folio, bdev,
1065 					(sector_t)index << sizebits, size);
1066 			goto done;
1067 		}
1068 		if (!try_to_free_buffers(folio))
1069 			goto failed;
1070 	}
1071 
1072 	bh = folio_alloc_buffers(folio, size, true);
1073 
1074 	/*
1075 	 * Link the folio to the buffers and initialise them.  Take the
1076 	 * lock to be atomic wrt __find_get_block(), which does not
1077 	 * run under the folio lock.
1078 	 */
1079 	spin_lock(&inode->i_mapping->private_lock);
1080 	link_dev_buffers(folio, bh);
1081 	end_block = folio_init_buffers(folio, bdev,
1082 			(sector_t)index << sizebits, size);
1083 	spin_unlock(&inode->i_mapping->private_lock);
1084 done:
1085 	ret = (block < end_block) ? 1 : -ENXIO;
1086 failed:
1087 	folio_unlock(folio);
1088 	folio_put(folio);
1089 	return ret;
1090 }
1091 
1092 /*
1093  * Create buffers for the specified block device block's page.  If
1094  * that page was dirty, the buffers are set dirty also.
1095  */
1096 static int
grow_buffers(struct block_device * bdev,sector_t block,int size,gfp_t gfp)1097 grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
1098 {
1099 	pgoff_t index;
1100 	int sizebits;
1101 
1102 	sizebits = PAGE_SHIFT - __ffs(size);
1103 	index = block >> sizebits;
1104 
1105 	/*
1106 	 * Check for a block which wants to lie outside our maximum possible
1107 	 * pagecache index.  (this comparison is done using sector_t types).
1108 	 */
1109 	if (unlikely(index != block >> sizebits)) {
1110 		printk(KERN_ERR "%s: requested out-of-range block %llu for "
1111 			"device %pg\n",
1112 			__func__, (unsigned long long)block,
1113 			bdev);
1114 		return -EIO;
1115 	}
1116 
1117 	/* Create a page with the proper size buffers.. */
1118 	return grow_dev_page(bdev, block, index, size, sizebits, gfp);
1119 }
1120 
1121 static struct buffer_head *
__getblk_slow(struct block_device * bdev,sector_t block,unsigned size,gfp_t gfp)1122 __getblk_slow(struct block_device *bdev, sector_t block,
1123 	     unsigned size, gfp_t gfp)
1124 {
1125 	/* Size must be multiple of hard sectorsize */
1126 	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1127 			(size < 512 || size > PAGE_SIZE))) {
1128 		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1129 					size);
1130 		printk(KERN_ERR "logical block size: %d\n",
1131 					bdev_logical_block_size(bdev));
1132 
1133 		dump_stack();
1134 		return NULL;
1135 	}
1136 
1137 	for (;;) {
1138 		struct buffer_head *bh;
1139 		int ret;
1140 
1141 		bh = __find_get_block(bdev, block, size);
1142 		if (bh)
1143 			return bh;
1144 
1145 		ret = grow_buffers(bdev, block, size, gfp);
1146 		if (ret < 0)
1147 			return NULL;
1148 	}
1149 }
1150 
1151 /*
1152  * The relationship between dirty buffers and dirty pages:
1153  *
1154  * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1155  * the page is tagged dirty in the page cache.
1156  *
1157  * At all times, the dirtiness of the buffers represents the dirtiness of
1158  * subsections of the page.  If the page has buffers, the page dirty bit is
1159  * merely a hint about the true dirty state.
1160  *
1161  * When a page is set dirty in its entirety, all its buffers are marked dirty
1162  * (if the page has buffers).
1163  *
1164  * When a buffer is marked dirty, its page is dirtied, but the page's other
1165  * buffers are not.
1166  *
1167  * Also.  When blockdev buffers are explicitly read with bread(), they
1168  * individually become uptodate.  But their backing page remains not
1169  * uptodate - even if all of its buffers are uptodate.  A subsequent
1170  * block_read_full_folio() against that folio will discover all the uptodate
1171  * buffers, will set the folio uptodate and will perform no I/O.
1172  */
1173 
1174 /**
1175  * mark_buffer_dirty - mark a buffer_head as needing writeout
1176  * @bh: the buffer_head to mark dirty
1177  *
1178  * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1179  * its backing page dirty, then tag the page as dirty in the page cache
1180  * and then attach the address_space's inode to its superblock's dirty
1181  * inode list.
1182  *
1183  * mark_buffer_dirty() is atomic.  It takes bh->b_folio->mapping->private_lock,
1184  * i_pages lock and mapping->host->i_lock.
1185  */
mark_buffer_dirty(struct buffer_head * bh)1186 void mark_buffer_dirty(struct buffer_head *bh)
1187 {
1188 	WARN_ON_ONCE(!buffer_uptodate(bh));
1189 
1190 	trace_block_dirty_buffer(bh);
1191 
1192 	/*
1193 	 * Very *carefully* optimize the it-is-already-dirty case.
1194 	 *
1195 	 * Don't let the final "is it dirty" escape to before we
1196 	 * perhaps modified the buffer.
1197 	 */
1198 	if (buffer_dirty(bh)) {
1199 		smp_mb();
1200 		if (buffer_dirty(bh))
1201 			return;
1202 	}
1203 
1204 	if (!test_set_buffer_dirty(bh)) {
1205 		struct folio *folio = bh->b_folio;
1206 		struct address_space *mapping = NULL;
1207 
1208 		folio_memcg_lock(folio);
1209 		if (!folio_test_set_dirty(folio)) {
1210 			mapping = folio->mapping;
1211 			if (mapping)
1212 				__folio_mark_dirty(folio, mapping, 0);
1213 		}
1214 		folio_memcg_unlock(folio);
1215 		if (mapping)
1216 			__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1217 	}
1218 }
1219 EXPORT_SYMBOL(mark_buffer_dirty);
1220 
mark_buffer_write_io_error(struct buffer_head * bh)1221 void mark_buffer_write_io_error(struct buffer_head *bh)
1222 {
1223 	set_buffer_write_io_error(bh);
1224 	/* FIXME: do we need to set this in both places? */
1225 	if (bh->b_folio && bh->b_folio->mapping)
1226 		mapping_set_error(bh->b_folio->mapping, -EIO);
1227 	if (bh->b_assoc_map) {
1228 		mapping_set_error(bh->b_assoc_map, -EIO);
1229 		errseq_set(&bh->b_assoc_map->host->i_sb->s_wb_err, -EIO);
1230 	}
1231 }
1232 EXPORT_SYMBOL(mark_buffer_write_io_error);
1233 
1234 /*
1235  * Decrement a buffer_head's reference count.  If all buffers against a page
1236  * have zero reference count, are clean and unlocked, and if the page is clean
1237  * and unlocked then try_to_free_buffers() may strip the buffers from the page
1238  * in preparation for freeing it (sometimes, rarely, buffers are removed from
1239  * a page but it ends up not being freed, and buffers may later be reattached).
1240  */
__brelse(struct buffer_head * buf)1241 void __brelse(struct buffer_head * buf)
1242 {
1243 	if (atomic_read(&buf->b_count)) {
1244 		put_bh(buf);
1245 		return;
1246 	}
1247 	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1248 }
1249 EXPORT_SYMBOL(__brelse);
1250 
1251 /*
1252  * bforget() is like brelse(), except it discards any
1253  * potentially dirty data.
1254  */
__bforget(struct buffer_head * bh)1255 void __bforget(struct buffer_head *bh)
1256 {
1257 	clear_buffer_dirty(bh);
1258 	if (bh->b_assoc_map) {
1259 		struct address_space *buffer_mapping = bh->b_folio->mapping;
1260 
1261 		spin_lock(&buffer_mapping->private_lock);
1262 		list_del_init(&bh->b_assoc_buffers);
1263 		bh->b_assoc_map = NULL;
1264 		spin_unlock(&buffer_mapping->private_lock);
1265 	}
1266 	__brelse(bh);
1267 }
1268 EXPORT_SYMBOL(__bforget);
1269 
__bread_slow(struct buffer_head * bh)1270 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1271 {
1272 	lock_buffer(bh);
1273 	if (buffer_uptodate(bh)) {
1274 		unlock_buffer(bh);
1275 		return bh;
1276 	} else {
1277 		get_bh(bh);
1278 		bh->b_end_io = end_buffer_read_sync;
1279 		submit_bh(REQ_OP_READ, bh);
1280 		wait_on_buffer(bh);
1281 		if (buffer_uptodate(bh))
1282 			return bh;
1283 	}
1284 	brelse(bh);
1285 	return NULL;
1286 }
1287 
1288 /*
1289  * Per-cpu buffer LRU implementation.  To reduce the cost of __find_get_block().
1290  * The bhs[] array is sorted - newest buffer is at bhs[0].  Buffers have their
1291  * refcount elevated by one when they're in an LRU.  A buffer can only appear
1292  * once in a particular CPU's LRU.  A single buffer can be present in multiple
1293  * CPU's LRUs at the same time.
1294  *
1295  * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1296  * sb_find_get_block().
1297  *
1298  * The LRUs themselves only need locking against invalidate_bh_lrus.  We use
1299  * a local interrupt disable for that.
1300  */
1301 
1302 #define BH_LRU_SIZE	16
1303 
1304 struct bh_lru {
1305 	struct buffer_head *bhs[BH_LRU_SIZE];
1306 };
1307 
1308 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1309 
1310 #ifdef CONFIG_SMP
1311 #define bh_lru_lock()	local_irq_disable()
1312 #define bh_lru_unlock()	local_irq_enable()
1313 #else
1314 #define bh_lru_lock()	preempt_disable()
1315 #define bh_lru_unlock()	preempt_enable()
1316 #endif
1317 
check_irqs_on(void)1318 static inline void check_irqs_on(void)
1319 {
1320 #ifdef irqs_disabled
1321 	BUG_ON(irqs_disabled());
1322 #endif
1323 }
1324 
1325 /*
1326  * Install a buffer_head into this cpu's LRU.  If not already in the LRU, it is
1327  * inserted at the front, and the buffer_head at the back if any is evicted.
1328  * Or, if already in the LRU it is moved to the front.
1329  */
bh_lru_install(struct buffer_head * bh)1330 static void bh_lru_install(struct buffer_head *bh)
1331 {
1332 	struct buffer_head *evictee = bh;
1333 	struct bh_lru *b;
1334 	int i;
1335 
1336 	check_irqs_on();
1337 	bh_lru_lock();
1338 
1339 	/*
1340 	 * the refcount of buffer_head in bh_lru prevents dropping the
1341 	 * attached page(i.e., try_to_free_buffers) so it could cause
1342 	 * failing page migration.
1343 	 * Skip putting upcoming bh into bh_lru until migration is done.
1344 	 */
1345 	if (lru_cache_disabled() || cpu_is_isolated(smp_processor_id())) {
1346 		bh_lru_unlock();
1347 		return;
1348 	}
1349 
1350 	b = this_cpu_ptr(&bh_lrus);
1351 	for (i = 0; i < BH_LRU_SIZE; i++) {
1352 		swap(evictee, b->bhs[i]);
1353 		if (evictee == bh) {
1354 			bh_lru_unlock();
1355 			return;
1356 		}
1357 	}
1358 
1359 	get_bh(bh);
1360 	bh_lru_unlock();
1361 	brelse(evictee);
1362 }
1363 
1364 /*
1365  * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
1366  */
1367 static struct buffer_head *
lookup_bh_lru(struct block_device * bdev,sector_t block,unsigned size)1368 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1369 {
1370 	struct buffer_head *ret = NULL;
1371 	unsigned int i;
1372 
1373 	check_irqs_on();
1374 	bh_lru_lock();
1375 	if (cpu_is_isolated(smp_processor_id())) {
1376 		bh_lru_unlock();
1377 		return NULL;
1378 	}
1379 	for (i = 0; i < BH_LRU_SIZE; i++) {
1380 		struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1381 
1382 		if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1383 		    bh->b_size == size) {
1384 			if (i) {
1385 				while (i) {
1386 					__this_cpu_write(bh_lrus.bhs[i],
1387 						__this_cpu_read(bh_lrus.bhs[i - 1]));
1388 					i--;
1389 				}
1390 				__this_cpu_write(bh_lrus.bhs[0], bh);
1391 			}
1392 			get_bh(bh);
1393 			ret = bh;
1394 			break;
1395 		}
1396 	}
1397 	bh_lru_unlock();
1398 	return ret;
1399 }
1400 
1401 /*
1402  * Perform a pagecache lookup for the matching buffer.  If it's there, refresh
1403  * it in the LRU and mark it as accessed.  If it is not present then return
1404  * NULL
1405  */
1406 struct buffer_head *
__find_get_block(struct block_device * bdev,sector_t block,unsigned size)1407 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1408 {
1409 	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1410 
1411 	if (bh == NULL) {
1412 		/* __find_get_block_slow will mark the page accessed */
1413 		bh = __find_get_block_slow(bdev, block);
1414 		if (bh)
1415 			bh_lru_install(bh);
1416 	} else
1417 		touch_buffer(bh);
1418 
1419 	return bh;
1420 }
1421 EXPORT_SYMBOL(__find_get_block);
1422 
1423 /*
1424  * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1425  * which corresponds to the passed block_device, block and size. The
1426  * returned buffer has its reference count incremented.
1427  *
1428  * __getblk_gfp() will lock up the machine if grow_dev_page's
1429  * try_to_free_buffers() attempt is failing.  FIXME, perhaps?
1430  */
1431 struct buffer_head *
__getblk_gfp(struct block_device * bdev,sector_t block,unsigned size,gfp_t gfp)1432 __getblk_gfp(struct block_device *bdev, sector_t block,
1433 	     unsigned size, gfp_t gfp)
1434 {
1435 	struct buffer_head *bh = __find_get_block(bdev, block, size);
1436 
1437 	might_sleep();
1438 	if (bh == NULL)
1439 		bh = __getblk_slow(bdev, block, size, gfp);
1440 	return bh;
1441 }
1442 EXPORT_SYMBOL(__getblk_gfp);
1443 
1444 /*
1445  * Do async read-ahead on a buffer..
1446  */
__breadahead(struct block_device * bdev,sector_t block,unsigned size)1447 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1448 {
1449 	struct buffer_head *bh = __getblk(bdev, block, size);
1450 	if (likely(bh)) {
1451 		bh_readahead(bh, REQ_RAHEAD);
1452 		brelse(bh);
1453 	}
1454 }
1455 EXPORT_SYMBOL(__breadahead);
1456 
1457 /**
1458  *  __bread_gfp() - reads a specified block and returns the bh
1459  *  @bdev: the block_device to read from
1460  *  @block: number of block
1461  *  @size: size (in bytes) to read
1462  *  @gfp: page allocation flag
1463  *
1464  *  Reads a specified block, and returns buffer head that contains it.
1465  *  The page cache can be allocated from non-movable area
1466  *  not to prevent page migration if you set gfp to zero.
1467  *  It returns NULL if the block was unreadable.
1468  */
1469 struct buffer_head *
__bread_gfp(struct block_device * bdev,sector_t block,unsigned size,gfp_t gfp)1470 __bread_gfp(struct block_device *bdev, sector_t block,
1471 		   unsigned size, gfp_t gfp)
1472 {
1473 	struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1474 
1475 	if (likely(bh) && !buffer_uptodate(bh))
1476 		bh = __bread_slow(bh);
1477 	return bh;
1478 }
1479 EXPORT_SYMBOL(__bread_gfp);
1480 
__invalidate_bh_lrus(struct bh_lru * b)1481 static void __invalidate_bh_lrus(struct bh_lru *b)
1482 {
1483 	int i;
1484 
1485 	for (i = 0; i < BH_LRU_SIZE; i++) {
1486 		brelse(b->bhs[i]);
1487 		b->bhs[i] = NULL;
1488 	}
1489 }
1490 /*
1491  * invalidate_bh_lrus() is called rarely - but not only at unmount.
1492  * This doesn't race because it runs in each cpu either in irq
1493  * or with preempt disabled.
1494  */
invalidate_bh_lru(void * arg)1495 static void invalidate_bh_lru(void *arg)
1496 {
1497 	struct bh_lru *b = &get_cpu_var(bh_lrus);
1498 
1499 	__invalidate_bh_lrus(b);
1500 	put_cpu_var(bh_lrus);
1501 }
1502 
has_bh_in_lru(int cpu,void * dummy)1503 bool has_bh_in_lru(int cpu, void *dummy)
1504 {
1505 	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1506 	int i;
1507 
1508 	for (i = 0; i < BH_LRU_SIZE; i++) {
1509 		if (b->bhs[i])
1510 			return true;
1511 	}
1512 
1513 	return false;
1514 }
1515 
invalidate_bh_lrus(void)1516 void invalidate_bh_lrus(void)
1517 {
1518 	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1);
1519 }
1520 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1521 
1522 /*
1523  * It's called from workqueue context so we need a bh_lru_lock to close
1524  * the race with preemption/irq.
1525  */
invalidate_bh_lrus_cpu(void)1526 void invalidate_bh_lrus_cpu(void)
1527 {
1528 	struct bh_lru *b;
1529 
1530 	bh_lru_lock();
1531 	b = this_cpu_ptr(&bh_lrus);
1532 	__invalidate_bh_lrus(b);
1533 	bh_lru_unlock();
1534 }
1535 
folio_set_bh(struct buffer_head * bh,struct folio * folio,unsigned long offset)1536 void folio_set_bh(struct buffer_head *bh, struct folio *folio,
1537 		  unsigned long offset)
1538 {
1539 	bh->b_folio = folio;
1540 	BUG_ON(offset >= folio_size(folio));
1541 	if (folio_test_highmem(folio))
1542 		/*
1543 		 * This catches illegal uses and preserves the offset:
1544 		 */
1545 		bh->b_data = (char *)(0 + offset);
1546 	else
1547 		bh->b_data = folio_address(folio) + offset;
1548 }
1549 EXPORT_SYMBOL(folio_set_bh);
1550 
1551 /*
1552  * Called when truncating a buffer on a page completely.
1553  */
1554 
1555 /* Bits that are cleared during an invalidate */
1556 #define BUFFER_FLAGS_DISCARD \
1557 	(1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1558 	 1 << BH_Delay | 1 << BH_Unwritten)
1559 
discard_buffer(struct buffer_head * bh)1560 static void discard_buffer(struct buffer_head * bh)
1561 {
1562 	unsigned long b_state;
1563 
1564 	lock_buffer(bh);
1565 	clear_buffer_dirty(bh);
1566 	bh->b_bdev = NULL;
1567 	b_state = READ_ONCE(bh->b_state);
1568 	do {
1569 	} while (!try_cmpxchg(&bh->b_state, &b_state,
1570 			      b_state & ~BUFFER_FLAGS_DISCARD));
1571 	unlock_buffer(bh);
1572 }
1573 
1574 /**
1575  * block_invalidate_folio - Invalidate part or all of a buffer-backed folio.
1576  * @folio: The folio which is affected.
1577  * @offset: start of the range to invalidate
1578  * @length: length of the range to invalidate
1579  *
1580  * block_invalidate_folio() is called when all or part of the folio has been
1581  * invalidated by a truncate operation.
1582  *
1583  * block_invalidate_folio() does not have to release all buffers, but it must
1584  * ensure that no dirty buffer is left outside @offset and that no I/O
1585  * is underway against any of the blocks which are outside the truncation
1586  * point.  Because the caller is about to free (and possibly reuse) those
1587  * blocks on-disk.
1588  */
block_invalidate_folio(struct folio * folio,size_t offset,size_t length)1589 void block_invalidate_folio(struct folio *folio, size_t offset, size_t length)
1590 {
1591 	struct buffer_head *head, *bh, *next;
1592 	size_t curr_off = 0;
1593 	size_t stop = length + offset;
1594 
1595 	BUG_ON(!folio_test_locked(folio));
1596 
1597 	/*
1598 	 * Check for overflow
1599 	 */
1600 	BUG_ON(stop > folio_size(folio) || stop < length);
1601 
1602 	head = folio_buffers(folio);
1603 	if (!head)
1604 		return;
1605 
1606 	bh = head;
1607 	do {
1608 		size_t next_off = curr_off + bh->b_size;
1609 		next = bh->b_this_page;
1610 
1611 		/*
1612 		 * Are we still fully in range ?
1613 		 */
1614 		if (next_off > stop)
1615 			goto out;
1616 
1617 		/*
1618 		 * is this block fully invalidated?
1619 		 */
1620 		if (offset <= curr_off)
1621 			discard_buffer(bh);
1622 		curr_off = next_off;
1623 		bh = next;
1624 	} while (bh != head);
1625 
1626 	/*
1627 	 * We release buffers only if the entire folio is being invalidated.
1628 	 * The get_block cached value has been unconditionally invalidated,
1629 	 * so real IO is not possible anymore.
1630 	 */
1631 	if (length == folio_size(folio))
1632 		filemap_release_folio(folio, 0);
1633 out:
1634 	return;
1635 }
1636 EXPORT_SYMBOL(block_invalidate_folio);
1637 
1638 /*
1639  * We attach and possibly dirty the buffers atomically wrt
1640  * block_dirty_folio() via private_lock.  try_to_free_buffers
1641  * is already excluded via the folio lock.
1642  */
folio_create_empty_buffers(struct folio * folio,unsigned long blocksize,unsigned long b_state)1643 void folio_create_empty_buffers(struct folio *folio, unsigned long blocksize,
1644 				unsigned long b_state)
1645 {
1646 	struct buffer_head *bh, *head, *tail;
1647 
1648 	head = folio_alloc_buffers(folio, blocksize, true);
1649 	bh = head;
1650 	do {
1651 		bh->b_state |= b_state;
1652 		tail = bh;
1653 		bh = bh->b_this_page;
1654 	} while (bh);
1655 	tail->b_this_page = head;
1656 
1657 	spin_lock(&folio->mapping->private_lock);
1658 	if (folio_test_uptodate(folio) || folio_test_dirty(folio)) {
1659 		bh = head;
1660 		do {
1661 			if (folio_test_dirty(folio))
1662 				set_buffer_dirty(bh);
1663 			if (folio_test_uptodate(folio))
1664 				set_buffer_uptodate(bh);
1665 			bh = bh->b_this_page;
1666 		} while (bh != head);
1667 	}
1668 	folio_attach_private(folio, head);
1669 	spin_unlock(&folio->mapping->private_lock);
1670 }
1671 EXPORT_SYMBOL(folio_create_empty_buffers);
1672 
create_empty_buffers(struct page * page,unsigned long blocksize,unsigned long b_state)1673 void create_empty_buffers(struct page *page,
1674 			unsigned long blocksize, unsigned long b_state)
1675 {
1676 	folio_create_empty_buffers(page_folio(page), blocksize, b_state);
1677 }
1678 EXPORT_SYMBOL(create_empty_buffers);
1679 
1680 /**
1681  * clean_bdev_aliases: clean a range of buffers in block device
1682  * @bdev: Block device to clean buffers in
1683  * @block: Start of a range of blocks to clean
1684  * @len: Number of blocks to clean
1685  *
1686  * We are taking a range of blocks for data and we don't want writeback of any
1687  * buffer-cache aliases starting from return from this function and until the
1688  * moment when something will explicitly mark the buffer dirty (hopefully that
1689  * will not happen until we will free that block ;-) We don't even need to mark
1690  * it not-uptodate - nobody can expect anything from a newly allocated buffer
1691  * anyway. We used to use unmap_buffer() for such invalidation, but that was
1692  * wrong. We definitely don't want to mark the alias unmapped, for example - it
1693  * would confuse anyone who might pick it with bread() afterwards...
1694  *
1695  * Also..  Note that bforget() doesn't lock the buffer.  So there can be
1696  * writeout I/O going on against recently-freed buffers.  We don't wait on that
1697  * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1698  * need to.  That happens here.
1699  */
clean_bdev_aliases(struct block_device * bdev,sector_t block,sector_t len)1700 void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1701 {
1702 	struct inode *bd_inode = bdev->bd_inode;
1703 	struct address_space *bd_mapping = bd_inode->i_mapping;
1704 	struct folio_batch fbatch;
1705 	pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
1706 	pgoff_t end;
1707 	int i, count;
1708 	struct buffer_head *bh;
1709 	struct buffer_head *head;
1710 
1711 	end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1712 	folio_batch_init(&fbatch);
1713 	while (filemap_get_folios(bd_mapping, &index, end, &fbatch)) {
1714 		count = folio_batch_count(&fbatch);
1715 		for (i = 0; i < count; i++) {
1716 			struct folio *folio = fbatch.folios[i];
1717 
1718 			if (!folio_buffers(folio))
1719 				continue;
1720 			/*
1721 			 * We use folio lock instead of bd_mapping->private_lock
1722 			 * to pin buffers here since we can afford to sleep and
1723 			 * it scales better than a global spinlock lock.
1724 			 */
1725 			folio_lock(folio);
1726 			/* Recheck when the folio is locked which pins bhs */
1727 			head = folio_buffers(folio);
1728 			if (!head)
1729 				goto unlock_page;
1730 			bh = head;
1731 			do {
1732 				if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1733 					goto next;
1734 				if (bh->b_blocknr >= block + len)
1735 					break;
1736 				clear_buffer_dirty(bh);
1737 				wait_on_buffer(bh);
1738 				clear_buffer_req(bh);
1739 next:
1740 				bh = bh->b_this_page;
1741 			} while (bh != head);
1742 unlock_page:
1743 			folio_unlock(folio);
1744 		}
1745 		folio_batch_release(&fbatch);
1746 		cond_resched();
1747 		/* End of range already reached? */
1748 		if (index > end || !index)
1749 			break;
1750 	}
1751 }
1752 EXPORT_SYMBOL(clean_bdev_aliases);
1753 
1754 /*
1755  * Size is a power-of-two in the range 512..PAGE_SIZE,
1756  * and the case we care about most is PAGE_SIZE.
1757  *
1758  * So this *could* possibly be written with those
1759  * constraints in mind (relevant mostly if some
1760  * architecture has a slow bit-scan instruction)
1761  */
block_size_bits(unsigned int blocksize)1762 static inline int block_size_bits(unsigned int blocksize)
1763 {
1764 	return ilog2(blocksize);
1765 }
1766 
folio_create_buffers(struct folio * folio,struct inode * inode,unsigned int b_state)1767 static struct buffer_head *folio_create_buffers(struct folio *folio,
1768 						struct inode *inode,
1769 						unsigned int b_state)
1770 {
1771 	BUG_ON(!folio_test_locked(folio));
1772 
1773 	if (!folio_buffers(folio))
1774 		folio_create_empty_buffers(folio,
1775 					   1 << READ_ONCE(inode->i_blkbits),
1776 					   b_state);
1777 	return folio_buffers(folio);
1778 }
1779 
1780 /*
1781  * NOTE! All mapped/uptodate combinations are valid:
1782  *
1783  *	Mapped	Uptodate	Meaning
1784  *
1785  *	No	No		"unknown" - must do get_block()
1786  *	No	Yes		"hole" - zero-filled
1787  *	Yes	No		"allocated" - allocated on disk, not read in
1788  *	Yes	Yes		"valid" - allocated and up-to-date in memory.
1789  *
1790  * "Dirty" is valid only with the last case (mapped+uptodate).
1791  */
1792 
1793 /*
1794  * While block_write_full_page is writing back the dirty buffers under
1795  * the page lock, whoever dirtied the buffers may decide to clean them
1796  * again at any time.  We handle that by only looking at the buffer
1797  * state inside lock_buffer().
1798  *
1799  * If block_write_full_page() is called for regular writeback
1800  * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1801  * locked buffer.   This only can happen if someone has written the buffer
1802  * directly, with submit_bh().  At the address_space level PageWriteback
1803  * prevents this contention from occurring.
1804  *
1805  * If block_write_full_page() is called with wbc->sync_mode ==
1806  * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1807  * causes the writes to be flagged as synchronous writes.
1808  */
__block_write_full_folio(struct inode * inode,struct folio * folio,get_block_t * get_block,struct writeback_control * wbc,bh_end_io_t * handler)1809 int __block_write_full_folio(struct inode *inode, struct folio *folio,
1810 			get_block_t *get_block, struct writeback_control *wbc,
1811 			bh_end_io_t *handler)
1812 {
1813 	int err;
1814 	sector_t block;
1815 	sector_t last_block;
1816 	struct buffer_head *bh, *head;
1817 	unsigned int blocksize, bbits;
1818 	int nr_underway = 0;
1819 	blk_opf_t write_flags = wbc_to_write_flags(wbc);
1820 
1821 	head = folio_create_buffers(folio, inode,
1822 				    (1 << BH_Dirty) | (1 << BH_Uptodate));
1823 
1824 	/*
1825 	 * Be very careful.  We have no exclusion from block_dirty_folio
1826 	 * here, and the (potentially unmapped) buffers may become dirty at
1827 	 * any time.  If a buffer becomes dirty here after we've inspected it
1828 	 * then we just miss that fact, and the folio stays dirty.
1829 	 *
1830 	 * Buffers outside i_size may be dirtied by block_dirty_folio;
1831 	 * handle that here by just cleaning them.
1832 	 */
1833 
1834 	bh = head;
1835 	blocksize = bh->b_size;
1836 	bbits = block_size_bits(blocksize);
1837 
1838 	block = (sector_t)folio->index << (PAGE_SHIFT - bbits);
1839 	last_block = (i_size_read(inode) - 1) >> bbits;
1840 
1841 	/*
1842 	 * Get all the dirty buffers mapped to disk addresses and
1843 	 * handle any aliases from the underlying blockdev's mapping.
1844 	 */
1845 	do {
1846 		if (block > last_block) {
1847 			/*
1848 			 * mapped buffers outside i_size will occur, because
1849 			 * this folio can be outside i_size when there is a
1850 			 * truncate in progress.
1851 			 */
1852 			/*
1853 			 * The buffer was zeroed by block_write_full_page()
1854 			 */
1855 			clear_buffer_dirty(bh);
1856 			set_buffer_uptodate(bh);
1857 		} else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1858 			   buffer_dirty(bh)) {
1859 			WARN_ON(bh->b_size != blocksize);
1860 			err = get_block(inode, block, bh, 1);
1861 			if (err)
1862 				goto recover;
1863 			clear_buffer_delay(bh);
1864 			if (buffer_new(bh)) {
1865 				/* blockdev mappings never come here */
1866 				clear_buffer_new(bh);
1867 				clean_bdev_bh_alias(bh);
1868 			}
1869 		}
1870 		bh = bh->b_this_page;
1871 		block++;
1872 	} while (bh != head);
1873 
1874 	do {
1875 		if (!buffer_mapped(bh))
1876 			continue;
1877 		/*
1878 		 * If it's a fully non-blocking write attempt and we cannot
1879 		 * lock the buffer then redirty the folio.  Note that this can
1880 		 * potentially cause a busy-wait loop from writeback threads
1881 		 * and kswapd activity, but those code paths have their own
1882 		 * higher-level throttling.
1883 		 */
1884 		if (wbc->sync_mode != WB_SYNC_NONE) {
1885 			lock_buffer(bh);
1886 		} else if (!trylock_buffer(bh)) {
1887 			folio_redirty_for_writepage(wbc, folio);
1888 			continue;
1889 		}
1890 		if (test_clear_buffer_dirty(bh)) {
1891 			mark_buffer_async_write_endio(bh, handler);
1892 		} else {
1893 			unlock_buffer(bh);
1894 		}
1895 	} while ((bh = bh->b_this_page) != head);
1896 
1897 	/*
1898 	 * The folio and its buffers are protected by the writeback flag,
1899 	 * so we can drop the bh refcounts early.
1900 	 */
1901 	BUG_ON(folio_test_writeback(folio));
1902 	folio_start_writeback(folio);
1903 
1904 	do {
1905 		struct buffer_head *next = bh->b_this_page;
1906 		if (buffer_async_write(bh)) {
1907 			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh, wbc);
1908 			nr_underway++;
1909 		}
1910 		bh = next;
1911 	} while (bh != head);
1912 	folio_unlock(folio);
1913 
1914 	err = 0;
1915 done:
1916 	if (nr_underway == 0) {
1917 		/*
1918 		 * The folio was marked dirty, but the buffers were
1919 		 * clean.  Someone wrote them back by hand with
1920 		 * write_dirty_buffer/submit_bh.  A rare case.
1921 		 */
1922 		folio_end_writeback(folio);
1923 
1924 		/*
1925 		 * The folio and buffer_heads can be released at any time from
1926 		 * here on.
1927 		 */
1928 	}
1929 	return err;
1930 
1931 recover:
1932 	/*
1933 	 * ENOSPC, or some other error.  We may already have added some
1934 	 * blocks to the file, so we need to write these out to avoid
1935 	 * exposing stale data.
1936 	 * The folio is currently locked and not marked for writeback
1937 	 */
1938 	bh = head;
1939 	/* Recovery: lock and submit the mapped buffers */
1940 	do {
1941 		if (buffer_mapped(bh) && buffer_dirty(bh) &&
1942 		    !buffer_delay(bh)) {
1943 			lock_buffer(bh);
1944 			mark_buffer_async_write_endio(bh, handler);
1945 		} else {
1946 			/*
1947 			 * The buffer may have been set dirty during
1948 			 * attachment to a dirty folio.
1949 			 */
1950 			clear_buffer_dirty(bh);
1951 		}
1952 	} while ((bh = bh->b_this_page) != head);
1953 	folio_set_error(folio);
1954 	BUG_ON(folio_test_writeback(folio));
1955 	mapping_set_error(folio->mapping, err);
1956 	folio_start_writeback(folio);
1957 	do {
1958 		struct buffer_head *next = bh->b_this_page;
1959 		if (buffer_async_write(bh)) {
1960 			clear_buffer_dirty(bh);
1961 			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh, wbc);
1962 			nr_underway++;
1963 		}
1964 		bh = next;
1965 	} while (bh != head);
1966 	folio_unlock(folio);
1967 	goto done;
1968 }
1969 EXPORT_SYMBOL(__block_write_full_folio);
1970 
1971 /*
1972  * If a folio has any new buffers, zero them out here, and mark them uptodate
1973  * and dirty so they'll be written out (in order to prevent uninitialised
1974  * block data from leaking). And clear the new bit.
1975  */
folio_zero_new_buffers(struct folio * folio,size_t from,size_t to)1976 void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to)
1977 {
1978 	size_t block_start, block_end;
1979 	struct buffer_head *head, *bh;
1980 
1981 	BUG_ON(!folio_test_locked(folio));
1982 	head = folio_buffers(folio);
1983 	if (!head)
1984 		return;
1985 
1986 	bh = head;
1987 	block_start = 0;
1988 	do {
1989 		block_end = block_start + bh->b_size;
1990 
1991 		if (buffer_new(bh)) {
1992 			if (block_end > from && block_start < to) {
1993 				if (!folio_test_uptodate(folio)) {
1994 					size_t start, xend;
1995 
1996 					start = max(from, block_start);
1997 					xend = min(to, block_end);
1998 
1999 					folio_zero_segment(folio, start, xend);
2000 					set_buffer_uptodate(bh);
2001 				}
2002 
2003 				clear_buffer_new(bh);
2004 				mark_buffer_dirty(bh);
2005 			}
2006 		}
2007 
2008 		block_start = block_end;
2009 		bh = bh->b_this_page;
2010 	} while (bh != head);
2011 }
2012 EXPORT_SYMBOL(folio_zero_new_buffers);
2013 
2014 static int
iomap_to_bh(struct inode * inode,sector_t block,struct buffer_head * bh,const struct iomap * iomap)2015 iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
2016 		const struct iomap *iomap)
2017 {
2018 	loff_t offset = block << inode->i_blkbits;
2019 
2020 	bh->b_bdev = iomap->bdev;
2021 
2022 	/*
2023 	 * Block points to offset in file we need to map, iomap contains
2024 	 * the offset at which the map starts. If the map ends before the
2025 	 * current block, then do not map the buffer and let the caller
2026 	 * handle it.
2027 	 */
2028 	if (offset >= iomap->offset + iomap->length)
2029 		return -EIO;
2030 
2031 	switch (iomap->type) {
2032 	case IOMAP_HOLE:
2033 		/*
2034 		 * If the buffer is not up to date or beyond the current EOF,
2035 		 * we need to mark it as new to ensure sub-block zeroing is
2036 		 * executed if necessary.
2037 		 */
2038 		if (!buffer_uptodate(bh) ||
2039 		    (offset >= i_size_read(inode)))
2040 			set_buffer_new(bh);
2041 		return 0;
2042 	case IOMAP_DELALLOC:
2043 		if (!buffer_uptodate(bh) ||
2044 		    (offset >= i_size_read(inode)))
2045 			set_buffer_new(bh);
2046 		set_buffer_uptodate(bh);
2047 		set_buffer_mapped(bh);
2048 		set_buffer_delay(bh);
2049 		return 0;
2050 	case IOMAP_UNWRITTEN:
2051 		/*
2052 		 * For unwritten regions, we always need to ensure that regions
2053 		 * in the block we are not writing to are zeroed. Mark the
2054 		 * buffer as new to ensure this.
2055 		 */
2056 		set_buffer_new(bh);
2057 		set_buffer_unwritten(bh);
2058 		fallthrough;
2059 	case IOMAP_MAPPED:
2060 		if ((iomap->flags & IOMAP_F_NEW) ||
2061 		    offset >= i_size_read(inode)) {
2062 			/*
2063 			 * This can happen if truncating the block device races
2064 			 * with the check in the caller as i_size updates on
2065 			 * block devices aren't synchronized by i_rwsem for
2066 			 * block devices.
2067 			 */
2068 			if (S_ISBLK(inode->i_mode))
2069 				return -EIO;
2070 			set_buffer_new(bh);
2071 		}
2072 		bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
2073 				inode->i_blkbits;
2074 		set_buffer_mapped(bh);
2075 		return 0;
2076 	default:
2077 		WARN_ON_ONCE(1);
2078 		return -EIO;
2079 	}
2080 }
2081 
__block_write_begin_int(struct folio * folio,loff_t pos,unsigned len,get_block_t * get_block,const struct iomap * iomap)2082 int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len,
2083 		get_block_t *get_block, const struct iomap *iomap)
2084 {
2085 	unsigned from = pos & (PAGE_SIZE - 1);
2086 	unsigned to = from + len;
2087 	struct inode *inode = folio->mapping->host;
2088 	unsigned block_start, block_end;
2089 	sector_t block;
2090 	int err = 0;
2091 	unsigned blocksize, bbits;
2092 	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
2093 
2094 	BUG_ON(!folio_test_locked(folio));
2095 	BUG_ON(from > PAGE_SIZE);
2096 	BUG_ON(to > PAGE_SIZE);
2097 	BUG_ON(from > to);
2098 
2099 	head = folio_create_buffers(folio, inode, 0);
2100 	blocksize = head->b_size;
2101 	bbits = block_size_bits(blocksize);
2102 
2103 	block = (sector_t)folio->index << (PAGE_SHIFT - bbits);
2104 
2105 	for(bh = head, block_start = 0; bh != head || !block_start;
2106 	    block++, block_start=block_end, bh = bh->b_this_page) {
2107 		block_end = block_start + blocksize;
2108 		if (block_end <= from || block_start >= to) {
2109 			if (folio_test_uptodate(folio)) {
2110 				if (!buffer_uptodate(bh))
2111 					set_buffer_uptodate(bh);
2112 			}
2113 			continue;
2114 		}
2115 		if (buffer_new(bh))
2116 			clear_buffer_new(bh);
2117 		if (!buffer_mapped(bh)) {
2118 			WARN_ON(bh->b_size != blocksize);
2119 			if (get_block)
2120 				err = get_block(inode, block, bh, 1);
2121 			else
2122 				err = iomap_to_bh(inode, block, bh, iomap);
2123 			if (err)
2124 				break;
2125 
2126 			if (buffer_new(bh)) {
2127 				clean_bdev_bh_alias(bh);
2128 				if (folio_test_uptodate(folio)) {
2129 					clear_buffer_new(bh);
2130 					set_buffer_uptodate(bh);
2131 					mark_buffer_dirty(bh);
2132 					continue;
2133 				}
2134 				if (block_end > to || block_start < from)
2135 					folio_zero_segments(folio,
2136 						to, block_end,
2137 						block_start, from);
2138 				continue;
2139 			}
2140 		}
2141 		if (folio_test_uptodate(folio)) {
2142 			if (!buffer_uptodate(bh))
2143 				set_buffer_uptodate(bh);
2144 			continue;
2145 		}
2146 		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2147 		    !buffer_unwritten(bh) &&
2148 		     (block_start < from || block_end > to)) {
2149 			bh_read_nowait(bh, 0);
2150 			*wait_bh++=bh;
2151 		}
2152 	}
2153 	/*
2154 	 * If we issued read requests - let them complete.
2155 	 */
2156 	while(wait_bh > wait) {
2157 		wait_on_buffer(*--wait_bh);
2158 		if (!buffer_uptodate(*wait_bh))
2159 			err = -EIO;
2160 	}
2161 	if (unlikely(err))
2162 		folio_zero_new_buffers(folio, from, to);
2163 	return err;
2164 }
2165 
__block_write_begin(struct page * page,loff_t pos,unsigned len,get_block_t * get_block)2166 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
2167 		get_block_t *get_block)
2168 {
2169 	return __block_write_begin_int(page_folio(page), pos, len, get_block,
2170 				       NULL);
2171 }
2172 EXPORT_SYMBOL(__block_write_begin);
2173 
__block_commit_write(struct folio * folio,size_t from,size_t to)2174 static void __block_commit_write(struct folio *folio, size_t from, size_t to)
2175 {
2176 	size_t block_start, block_end;
2177 	bool partial = false;
2178 	unsigned blocksize;
2179 	struct buffer_head *bh, *head;
2180 
2181 	bh = head = folio_buffers(folio);
2182 	blocksize = bh->b_size;
2183 
2184 	block_start = 0;
2185 	do {
2186 		block_end = block_start + blocksize;
2187 		if (block_end <= from || block_start >= to) {
2188 			if (!buffer_uptodate(bh))
2189 				partial = true;
2190 		} else {
2191 			set_buffer_uptodate(bh);
2192 			mark_buffer_dirty(bh);
2193 		}
2194 		if (buffer_new(bh))
2195 			clear_buffer_new(bh);
2196 
2197 		block_start = block_end;
2198 		bh = bh->b_this_page;
2199 	} while (bh != head);
2200 
2201 	/*
2202 	 * If this is a partial write which happened to make all buffers
2203 	 * uptodate then we can optimize away a bogus read_folio() for
2204 	 * the next read(). Here we 'discover' whether the folio went
2205 	 * uptodate as a result of this (potentially partial) write.
2206 	 */
2207 	if (!partial)
2208 		folio_mark_uptodate(folio);
2209 }
2210 
2211 /*
2212  * block_write_begin takes care of the basic task of block allocation and
2213  * bringing partial write blocks uptodate first.
2214  *
2215  * The filesystem needs to handle block truncation upon failure.
2216  */
block_write_begin(struct address_space * mapping,loff_t pos,unsigned len,struct page ** pagep,get_block_t * get_block)2217 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2218 		struct page **pagep, get_block_t *get_block)
2219 {
2220 	pgoff_t index = pos >> PAGE_SHIFT;
2221 	struct page *page;
2222 	int status;
2223 
2224 	page = grab_cache_page_write_begin(mapping, index);
2225 	if (!page)
2226 		return -ENOMEM;
2227 
2228 	status = __block_write_begin(page, pos, len, get_block);
2229 	if (unlikely(status)) {
2230 		unlock_page(page);
2231 		put_page(page);
2232 		page = NULL;
2233 	}
2234 
2235 	*pagep = page;
2236 	return status;
2237 }
2238 EXPORT_SYMBOL(block_write_begin);
2239 
block_write_end(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned copied,struct page * page,void * fsdata)2240 int block_write_end(struct file *file, struct address_space *mapping,
2241 			loff_t pos, unsigned len, unsigned copied,
2242 			struct page *page, void *fsdata)
2243 {
2244 	struct folio *folio = page_folio(page);
2245 	size_t start = pos - folio_pos(folio);
2246 
2247 	if (unlikely(copied < len)) {
2248 		/*
2249 		 * The buffers that were written will now be uptodate, so
2250 		 * we don't have to worry about a read_folio reading them
2251 		 * and overwriting a partial write. However if we have
2252 		 * encountered a short write and only partially written
2253 		 * into a buffer, it will not be marked uptodate, so a
2254 		 * read_folio might come in and destroy our partial write.
2255 		 *
2256 		 * Do the simplest thing, and just treat any short write to a
2257 		 * non uptodate folio as a zero-length write, and force the
2258 		 * caller to redo the whole thing.
2259 		 */
2260 		if (!folio_test_uptodate(folio))
2261 			copied = 0;
2262 
2263 		folio_zero_new_buffers(folio, start+copied, start+len);
2264 	}
2265 	flush_dcache_folio(folio);
2266 
2267 	/* This could be a short (even 0-length) commit */
2268 	__block_commit_write(folio, start, start + copied);
2269 
2270 	return copied;
2271 }
2272 EXPORT_SYMBOL(block_write_end);
2273 
generic_write_end(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned copied,struct page * page,void * fsdata)2274 int generic_write_end(struct file *file, struct address_space *mapping,
2275 			loff_t pos, unsigned len, unsigned copied,
2276 			struct page *page, void *fsdata)
2277 {
2278 	struct inode *inode = mapping->host;
2279 	loff_t old_size = inode->i_size;
2280 	bool i_size_changed = false;
2281 
2282 	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2283 
2284 	/*
2285 	 * No need to use i_size_read() here, the i_size cannot change under us
2286 	 * because we hold i_rwsem.
2287 	 *
2288 	 * But it's important to update i_size while still holding page lock:
2289 	 * page writeout could otherwise come in and zero beyond i_size.
2290 	 */
2291 	if (pos + copied > inode->i_size) {
2292 		i_size_write(inode, pos + copied);
2293 		i_size_changed = true;
2294 	}
2295 
2296 	unlock_page(page);
2297 	put_page(page);
2298 
2299 	if (old_size < pos)
2300 		pagecache_isize_extended(inode, old_size, pos);
2301 	/*
2302 	 * Don't mark the inode dirty under page lock. First, it unnecessarily
2303 	 * makes the holding time of page lock longer. Second, it forces lock
2304 	 * ordering of page lock and transaction start for journaling
2305 	 * filesystems.
2306 	 */
2307 	if (i_size_changed)
2308 		mark_inode_dirty(inode);
2309 	return copied;
2310 }
2311 EXPORT_SYMBOL(generic_write_end);
2312 
2313 /*
2314  * block_is_partially_uptodate checks whether buffers within a folio are
2315  * uptodate or not.
2316  *
2317  * Returns true if all buffers which correspond to the specified part
2318  * of the folio are uptodate.
2319  */
block_is_partially_uptodate(struct folio * folio,size_t from,size_t count)2320 bool block_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
2321 {
2322 	unsigned block_start, block_end, blocksize;
2323 	unsigned to;
2324 	struct buffer_head *bh, *head;
2325 	bool ret = true;
2326 
2327 	head = folio_buffers(folio);
2328 	if (!head)
2329 		return false;
2330 	blocksize = head->b_size;
2331 	to = min_t(unsigned, folio_size(folio) - from, count);
2332 	to = from + to;
2333 	if (from < blocksize && to > folio_size(folio) - blocksize)
2334 		return false;
2335 
2336 	bh = head;
2337 	block_start = 0;
2338 	do {
2339 		block_end = block_start + blocksize;
2340 		if (block_end > from && block_start < to) {
2341 			if (!buffer_uptodate(bh)) {
2342 				ret = false;
2343 				break;
2344 			}
2345 			if (block_end >= to)
2346 				break;
2347 		}
2348 		block_start = block_end;
2349 		bh = bh->b_this_page;
2350 	} while (bh != head);
2351 
2352 	return ret;
2353 }
2354 EXPORT_SYMBOL(block_is_partially_uptodate);
2355 
2356 /*
2357  * Generic "read_folio" function for block devices that have the normal
2358  * get_block functionality. This is most of the block device filesystems.
2359  * Reads the folio asynchronously --- the unlock_buffer() and
2360  * set/clear_buffer_uptodate() functions propagate buffer state into the
2361  * folio once IO has completed.
2362  */
block_read_full_folio(struct folio * folio,get_block_t * get_block)2363 int block_read_full_folio(struct folio *folio, get_block_t *get_block)
2364 {
2365 	struct inode *inode = folio->mapping->host;
2366 	sector_t iblock, lblock;
2367 	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2368 	unsigned int blocksize, bbits;
2369 	int nr, i;
2370 	int fully_mapped = 1;
2371 	bool page_error = false;
2372 	loff_t limit = i_size_read(inode);
2373 
2374 	/* This is needed for ext4. */
2375 	if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
2376 		limit = inode->i_sb->s_maxbytes;
2377 
2378 	VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
2379 
2380 	head = folio_create_buffers(folio, inode, 0);
2381 	blocksize = head->b_size;
2382 	bbits = block_size_bits(blocksize);
2383 
2384 	iblock = (sector_t)folio->index << (PAGE_SHIFT - bbits);
2385 	lblock = (limit+blocksize-1) >> bbits;
2386 	bh = head;
2387 	nr = 0;
2388 	i = 0;
2389 
2390 	do {
2391 		if (buffer_uptodate(bh))
2392 			continue;
2393 
2394 		if (!buffer_mapped(bh)) {
2395 			int err = 0;
2396 
2397 			fully_mapped = 0;
2398 			if (iblock < lblock) {
2399 				WARN_ON(bh->b_size != blocksize);
2400 				err = get_block(inode, iblock, bh, 0);
2401 				if (err) {
2402 					folio_set_error(folio);
2403 					page_error = true;
2404 				}
2405 			}
2406 			if (!buffer_mapped(bh)) {
2407 				folio_zero_range(folio, i * blocksize,
2408 						blocksize);
2409 				if (!err)
2410 					set_buffer_uptodate(bh);
2411 				continue;
2412 			}
2413 			/*
2414 			 * get_block() might have updated the buffer
2415 			 * synchronously
2416 			 */
2417 			if (buffer_uptodate(bh))
2418 				continue;
2419 		}
2420 		arr[nr++] = bh;
2421 	} while (i++, iblock++, (bh = bh->b_this_page) != head);
2422 
2423 	if (fully_mapped)
2424 		folio_set_mappedtodisk(folio);
2425 
2426 	if (!nr) {
2427 		/*
2428 		 * All buffers are uptodate - we can set the folio uptodate
2429 		 * as well. But not if get_block() returned an error.
2430 		 */
2431 		if (!page_error)
2432 			folio_mark_uptodate(folio);
2433 		folio_unlock(folio);
2434 		return 0;
2435 	}
2436 
2437 	/* Stage two: lock the buffers */
2438 	for (i = 0; i < nr; i++) {
2439 		bh = arr[i];
2440 		lock_buffer(bh);
2441 		mark_buffer_async_read(bh);
2442 	}
2443 
2444 	/*
2445 	 * Stage 3: start the IO.  Check for uptodateness
2446 	 * inside the buffer lock in case another process reading
2447 	 * the underlying blockdev brought it uptodate (the sct fix).
2448 	 */
2449 	for (i = 0; i < nr; i++) {
2450 		bh = arr[i];
2451 		if (buffer_uptodate(bh))
2452 			end_buffer_async_read(bh, 1);
2453 		else
2454 			submit_bh(REQ_OP_READ, bh);
2455 	}
2456 	return 0;
2457 }
2458 EXPORT_SYMBOL(block_read_full_folio);
2459 
2460 /* utility function for filesystems that need to do work on expanding
2461  * truncates.  Uses filesystem pagecache writes to allow the filesystem to
2462  * deal with the hole.
2463  */
generic_cont_expand_simple(struct inode * inode,loff_t size)2464 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2465 {
2466 	struct address_space *mapping = inode->i_mapping;
2467 	const struct address_space_operations *aops = mapping->a_ops;
2468 	struct page *page;
2469 	void *fsdata = NULL;
2470 	int err;
2471 
2472 	err = inode_newsize_ok(inode, size);
2473 	if (err)
2474 		goto out;
2475 
2476 	err = aops->write_begin(NULL, mapping, size, 0, &page, &fsdata);
2477 	if (err)
2478 		goto out;
2479 
2480 	err = aops->write_end(NULL, mapping, size, 0, 0, page, fsdata);
2481 	BUG_ON(err > 0);
2482 
2483 out:
2484 	return err;
2485 }
2486 EXPORT_SYMBOL(generic_cont_expand_simple);
2487 
cont_expand_zero(struct file * file,struct address_space * mapping,loff_t pos,loff_t * bytes)2488 static int cont_expand_zero(struct file *file, struct address_space *mapping,
2489 			    loff_t pos, loff_t *bytes)
2490 {
2491 	struct inode *inode = mapping->host;
2492 	const struct address_space_operations *aops = mapping->a_ops;
2493 	unsigned int blocksize = i_blocksize(inode);
2494 	struct page *page;
2495 	void *fsdata = NULL;
2496 	pgoff_t index, curidx;
2497 	loff_t curpos;
2498 	unsigned zerofrom, offset, len;
2499 	int err = 0;
2500 
2501 	index = pos >> PAGE_SHIFT;
2502 	offset = pos & ~PAGE_MASK;
2503 
2504 	while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2505 		zerofrom = curpos & ~PAGE_MASK;
2506 		if (zerofrom & (blocksize-1)) {
2507 			*bytes |= (blocksize-1);
2508 			(*bytes)++;
2509 		}
2510 		len = PAGE_SIZE - zerofrom;
2511 
2512 		err = aops->write_begin(file, mapping, curpos, len,
2513 					    &page, &fsdata);
2514 		if (err)
2515 			goto out;
2516 		zero_user(page, zerofrom, len);
2517 		err = aops->write_end(file, mapping, curpos, len, len,
2518 						page, fsdata);
2519 		if (err < 0)
2520 			goto out;
2521 		BUG_ON(err != len);
2522 		err = 0;
2523 
2524 		balance_dirty_pages_ratelimited(mapping);
2525 
2526 		if (fatal_signal_pending(current)) {
2527 			err = -EINTR;
2528 			goto out;
2529 		}
2530 	}
2531 
2532 	/* page covers the boundary, find the boundary offset */
2533 	if (index == curidx) {
2534 		zerofrom = curpos & ~PAGE_MASK;
2535 		/* if we will expand the thing last block will be filled */
2536 		if (offset <= zerofrom) {
2537 			goto out;
2538 		}
2539 		if (zerofrom & (blocksize-1)) {
2540 			*bytes |= (blocksize-1);
2541 			(*bytes)++;
2542 		}
2543 		len = offset - zerofrom;
2544 
2545 		err = aops->write_begin(file, mapping, curpos, len,
2546 					    &page, &fsdata);
2547 		if (err)
2548 			goto out;
2549 		zero_user(page, zerofrom, len);
2550 		err = aops->write_end(file, mapping, curpos, len, len,
2551 						page, fsdata);
2552 		if (err < 0)
2553 			goto out;
2554 		BUG_ON(err != len);
2555 		err = 0;
2556 	}
2557 out:
2558 	return err;
2559 }
2560 
2561 /*
2562  * For moronic filesystems that do not allow holes in file.
2563  * We may have to extend the file.
2564  */
cont_write_begin(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,struct page ** pagep,void ** fsdata,get_block_t * get_block,loff_t * bytes)2565 int cont_write_begin(struct file *file, struct address_space *mapping,
2566 			loff_t pos, unsigned len,
2567 			struct page **pagep, void **fsdata,
2568 			get_block_t *get_block, loff_t *bytes)
2569 {
2570 	struct inode *inode = mapping->host;
2571 	unsigned int blocksize = i_blocksize(inode);
2572 	unsigned int zerofrom;
2573 	int err;
2574 
2575 	err = cont_expand_zero(file, mapping, pos, bytes);
2576 	if (err)
2577 		return err;
2578 
2579 	zerofrom = *bytes & ~PAGE_MASK;
2580 	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2581 		*bytes |= (blocksize-1);
2582 		(*bytes)++;
2583 	}
2584 
2585 	return block_write_begin(mapping, pos, len, pagep, get_block);
2586 }
2587 EXPORT_SYMBOL(cont_write_begin);
2588 
block_commit_write(struct page * page,unsigned from,unsigned to)2589 void block_commit_write(struct page *page, unsigned from, unsigned to)
2590 {
2591 	struct folio *folio = page_folio(page);
2592 	__block_commit_write(folio, from, to);
2593 }
2594 EXPORT_SYMBOL(block_commit_write);
2595 
2596 /*
2597  * block_page_mkwrite() is not allowed to change the file size as it gets
2598  * called from a page fault handler when a page is first dirtied. Hence we must
2599  * be careful to check for EOF conditions here. We set the page up correctly
2600  * for a written page which means we get ENOSPC checking when writing into
2601  * holes and correct delalloc and unwritten extent mapping on filesystems that
2602  * support these features.
2603  *
2604  * We are not allowed to take the i_mutex here so we have to play games to
2605  * protect against truncate races as the page could now be beyond EOF.  Because
2606  * truncate writes the inode size before removing pages, once we have the
2607  * page lock we can determine safely if the page is beyond EOF. If it is not
2608  * beyond EOF, then the page is guaranteed safe against truncation until we
2609  * unlock the page.
2610  *
2611  * Direct callers of this function should protect against filesystem freezing
2612  * using sb_start_pagefault() - sb_end_pagefault() functions.
2613  */
block_page_mkwrite(struct vm_area_struct * vma,struct vm_fault * vmf,get_block_t get_block)2614 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2615 			 get_block_t get_block)
2616 {
2617 	struct folio *folio = page_folio(vmf->page);
2618 	struct inode *inode = file_inode(vma->vm_file);
2619 	unsigned long end;
2620 	loff_t size;
2621 	int ret;
2622 
2623 	folio_lock(folio);
2624 	size = i_size_read(inode);
2625 	if ((folio->mapping != inode->i_mapping) ||
2626 	    (folio_pos(folio) >= size)) {
2627 		/* We overload EFAULT to mean page got truncated */
2628 		ret = -EFAULT;
2629 		goto out_unlock;
2630 	}
2631 
2632 	end = folio_size(folio);
2633 	/* folio is wholly or partially inside EOF */
2634 	if (folio_pos(folio) + end > size)
2635 		end = size - folio_pos(folio);
2636 
2637 	ret = __block_write_begin_int(folio, 0, end, get_block, NULL);
2638 	if (unlikely(ret))
2639 		goto out_unlock;
2640 
2641 	__block_commit_write(folio, 0, end);
2642 
2643 	folio_mark_dirty(folio);
2644 	folio_wait_stable(folio);
2645 	return 0;
2646 out_unlock:
2647 	folio_unlock(folio);
2648 	return ret;
2649 }
2650 EXPORT_SYMBOL(block_page_mkwrite);
2651 
block_truncate_page(struct address_space * mapping,loff_t from,get_block_t * get_block)2652 int block_truncate_page(struct address_space *mapping,
2653 			loff_t from, get_block_t *get_block)
2654 {
2655 	pgoff_t index = from >> PAGE_SHIFT;
2656 	unsigned blocksize;
2657 	sector_t iblock;
2658 	size_t offset, length, pos;
2659 	struct inode *inode = mapping->host;
2660 	struct folio *folio;
2661 	struct buffer_head *bh;
2662 	int err = 0;
2663 
2664 	blocksize = i_blocksize(inode);
2665 	length = from & (blocksize - 1);
2666 
2667 	/* Block boundary? Nothing to do */
2668 	if (!length)
2669 		return 0;
2670 
2671 	length = blocksize - length;
2672 	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2673 
2674 	folio = filemap_grab_folio(mapping, index);
2675 	if (IS_ERR(folio))
2676 		return PTR_ERR(folio);
2677 
2678 	bh = folio_buffers(folio);
2679 	if (!bh) {
2680 		folio_create_empty_buffers(folio, blocksize, 0);
2681 		bh = folio_buffers(folio);
2682 	}
2683 
2684 	/* Find the buffer that contains "offset" */
2685 	offset = offset_in_folio(folio, from);
2686 	pos = blocksize;
2687 	while (offset >= pos) {
2688 		bh = bh->b_this_page;
2689 		iblock++;
2690 		pos += blocksize;
2691 	}
2692 
2693 	if (!buffer_mapped(bh)) {
2694 		WARN_ON(bh->b_size != blocksize);
2695 		err = get_block(inode, iblock, bh, 0);
2696 		if (err)
2697 			goto unlock;
2698 		/* unmapped? It's a hole - nothing to do */
2699 		if (!buffer_mapped(bh))
2700 			goto unlock;
2701 	}
2702 
2703 	/* Ok, it's mapped. Make sure it's up-to-date */
2704 	if (folio_test_uptodate(folio))
2705 		set_buffer_uptodate(bh);
2706 
2707 	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2708 		err = bh_read(bh, 0);
2709 		/* Uhhuh. Read error. Complain and punt. */
2710 		if (err < 0)
2711 			goto unlock;
2712 	}
2713 
2714 	folio_zero_range(folio, offset, length);
2715 	mark_buffer_dirty(bh);
2716 
2717 unlock:
2718 	folio_unlock(folio);
2719 	folio_put(folio);
2720 
2721 	return err;
2722 }
2723 EXPORT_SYMBOL(block_truncate_page);
2724 
2725 /*
2726  * The generic ->writepage function for buffer-backed address_spaces
2727  */
block_write_full_page(struct page * page,get_block_t * get_block,struct writeback_control * wbc)2728 int block_write_full_page(struct page *page, get_block_t *get_block,
2729 			struct writeback_control *wbc)
2730 {
2731 	struct folio *folio = page_folio(page);
2732 	struct inode * const inode = folio->mapping->host;
2733 	loff_t i_size = i_size_read(inode);
2734 
2735 	/* Is the folio fully inside i_size? */
2736 	if (folio_pos(folio) + folio_size(folio) <= i_size)
2737 		return __block_write_full_folio(inode, folio, get_block, wbc,
2738 					       end_buffer_async_write);
2739 
2740 	/* Is the folio fully outside i_size? (truncate in progress) */
2741 	if (folio_pos(folio) >= i_size) {
2742 		folio_unlock(folio);
2743 		return 0; /* don't care */
2744 	}
2745 
2746 	/*
2747 	 * The folio straddles i_size.  It must be zeroed out on each and every
2748 	 * writepage invocation because it may be mmapped.  "A file is mapped
2749 	 * in multiples of the page size.  For a file that is not a multiple of
2750 	 * the page size, the remaining memory is zeroed when mapped, and
2751 	 * writes to that region are not written out to the file."
2752 	 */
2753 	folio_zero_segment(folio, offset_in_folio(folio, i_size),
2754 			folio_size(folio));
2755 	return __block_write_full_folio(inode, folio, get_block, wbc,
2756 			end_buffer_async_write);
2757 }
2758 EXPORT_SYMBOL(block_write_full_page);
2759 
generic_block_bmap(struct address_space * mapping,sector_t block,get_block_t * get_block)2760 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2761 			    get_block_t *get_block)
2762 {
2763 	struct inode *inode = mapping->host;
2764 	struct buffer_head tmp = {
2765 		.b_size = i_blocksize(inode),
2766 	};
2767 
2768 	get_block(inode, block, &tmp, 0);
2769 	return tmp.b_blocknr;
2770 }
2771 EXPORT_SYMBOL(generic_block_bmap);
2772 
end_bio_bh_io_sync(struct bio * bio)2773 static void end_bio_bh_io_sync(struct bio *bio)
2774 {
2775 	struct buffer_head *bh = bio->bi_private;
2776 
2777 	if (unlikely(bio_flagged(bio, BIO_QUIET)))
2778 		set_bit(BH_Quiet, &bh->b_state);
2779 
2780 	bh->b_end_io(bh, !bio->bi_status);
2781 	bio_put(bio);
2782 }
2783 
submit_bh_wbc(blk_opf_t opf,struct buffer_head * bh,struct writeback_control * wbc)2784 static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
2785 			  struct writeback_control *wbc)
2786 {
2787 	const enum req_op op = opf & REQ_OP_MASK;
2788 	struct bio *bio;
2789 
2790 	BUG_ON(!buffer_locked(bh));
2791 	BUG_ON(!buffer_mapped(bh));
2792 	BUG_ON(!bh->b_end_io);
2793 	BUG_ON(buffer_delay(bh));
2794 	BUG_ON(buffer_unwritten(bh));
2795 
2796 	/*
2797 	 * Only clear out a write error when rewriting
2798 	 */
2799 	if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
2800 		clear_buffer_write_io_error(bh);
2801 
2802 	if (buffer_meta(bh))
2803 		opf |= REQ_META;
2804 	if (buffer_prio(bh))
2805 		opf |= REQ_PRIO;
2806 
2807 	bio = bio_alloc(bh->b_bdev, 1, opf, GFP_NOIO);
2808 
2809 	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
2810 
2811 	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2812 
2813 	__bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
2814 
2815 	bio->bi_end_io = end_bio_bh_io_sync;
2816 	bio->bi_private = bh;
2817 
2818 	/* Take care of bh's that straddle the end of the device */
2819 	guard_bio_eod(bio);
2820 
2821 	if (wbc) {
2822 		wbc_init_bio(wbc, bio);
2823 		wbc_account_cgroup_owner(wbc, bh->b_page, bh->b_size);
2824 	}
2825 
2826 	submit_bio(bio);
2827 }
2828 
submit_bh(blk_opf_t opf,struct buffer_head * bh)2829 void submit_bh(blk_opf_t opf, struct buffer_head *bh)
2830 {
2831 	submit_bh_wbc(opf, bh, NULL);
2832 }
2833 EXPORT_SYMBOL(submit_bh);
2834 
write_dirty_buffer(struct buffer_head * bh,blk_opf_t op_flags)2835 void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2836 {
2837 	lock_buffer(bh);
2838 	if (!test_clear_buffer_dirty(bh)) {
2839 		unlock_buffer(bh);
2840 		return;
2841 	}
2842 	bh->b_end_io = end_buffer_write_sync;
2843 	get_bh(bh);
2844 	submit_bh(REQ_OP_WRITE | op_flags, bh);
2845 }
2846 EXPORT_SYMBOL(write_dirty_buffer);
2847 
2848 /*
2849  * For a data-integrity writeout, we need to wait upon any in-progress I/O
2850  * and then start new I/O and then wait upon it.  The caller must have a ref on
2851  * the buffer_head.
2852  */
__sync_dirty_buffer(struct buffer_head * bh,blk_opf_t op_flags)2853 int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2854 {
2855 	WARN_ON(atomic_read(&bh->b_count) < 1);
2856 	lock_buffer(bh);
2857 	if (test_clear_buffer_dirty(bh)) {
2858 		/*
2859 		 * The bh should be mapped, but it might not be if the
2860 		 * device was hot-removed. Not much we can do but fail the I/O.
2861 		 */
2862 		if (!buffer_mapped(bh)) {
2863 			unlock_buffer(bh);
2864 			return -EIO;
2865 		}
2866 
2867 		get_bh(bh);
2868 		bh->b_end_io = end_buffer_write_sync;
2869 		submit_bh(REQ_OP_WRITE | op_flags, bh);
2870 		wait_on_buffer(bh);
2871 		if (!buffer_uptodate(bh))
2872 			return -EIO;
2873 	} else {
2874 		unlock_buffer(bh);
2875 	}
2876 	return 0;
2877 }
2878 EXPORT_SYMBOL(__sync_dirty_buffer);
2879 
sync_dirty_buffer(struct buffer_head * bh)2880 int sync_dirty_buffer(struct buffer_head *bh)
2881 {
2882 	return __sync_dirty_buffer(bh, REQ_SYNC);
2883 }
2884 EXPORT_SYMBOL(sync_dirty_buffer);
2885 
2886 /*
2887  * try_to_free_buffers() checks if all the buffers on this particular folio
2888  * are unused, and releases them if so.
2889  *
2890  * Exclusion against try_to_free_buffers may be obtained by either
2891  * locking the folio or by holding its mapping's private_lock.
2892  *
2893  * If the folio is dirty but all the buffers are clean then we need to
2894  * be sure to mark the folio clean as well.  This is because the folio
2895  * may be against a block device, and a later reattachment of buffers
2896  * to a dirty folio will set *all* buffers dirty.  Which would corrupt
2897  * filesystem data on the same device.
2898  *
2899  * The same applies to regular filesystem folios: if all the buffers are
2900  * clean then we set the folio clean and proceed.  To do that, we require
2901  * total exclusion from block_dirty_folio().  That is obtained with
2902  * private_lock.
2903  *
2904  * try_to_free_buffers() is non-blocking.
2905  */
buffer_busy(struct buffer_head * bh)2906 static inline int buffer_busy(struct buffer_head *bh)
2907 {
2908 	return atomic_read(&bh->b_count) |
2909 		(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2910 }
2911 
2912 static bool
drop_buffers(struct folio * folio,struct buffer_head ** buffers_to_free)2913 drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
2914 {
2915 	struct buffer_head *head = folio_buffers(folio);
2916 	struct buffer_head *bh;
2917 
2918 	bh = head;
2919 	do {
2920 		if (buffer_busy(bh))
2921 			goto failed;
2922 		bh = bh->b_this_page;
2923 	} while (bh != head);
2924 
2925 	do {
2926 		struct buffer_head *next = bh->b_this_page;
2927 
2928 		if (bh->b_assoc_map)
2929 			__remove_assoc_queue(bh);
2930 		bh = next;
2931 	} while (bh != head);
2932 	*buffers_to_free = head;
2933 	folio_detach_private(folio);
2934 	return true;
2935 failed:
2936 	return false;
2937 }
2938 
try_to_free_buffers(struct folio * folio)2939 bool try_to_free_buffers(struct folio *folio)
2940 {
2941 	struct address_space * const mapping = folio->mapping;
2942 	struct buffer_head *buffers_to_free = NULL;
2943 	bool ret = 0;
2944 
2945 	BUG_ON(!folio_test_locked(folio));
2946 	if (folio_test_writeback(folio))
2947 		return false;
2948 
2949 	if (mapping == NULL) {		/* can this still happen? */
2950 		ret = drop_buffers(folio, &buffers_to_free);
2951 		goto out;
2952 	}
2953 
2954 	spin_lock(&mapping->private_lock);
2955 	ret = drop_buffers(folio, &buffers_to_free);
2956 
2957 	/*
2958 	 * If the filesystem writes its buffers by hand (eg ext3)
2959 	 * then we can have clean buffers against a dirty folio.  We
2960 	 * clean the folio here; otherwise the VM will never notice
2961 	 * that the filesystem did any IO at all.
2962 	 *
2963 	 * Also, during truncate, discard_buffer will have marked all
2964 	 * the folio's buffers clean.  We discover that here and clean
2965 	 * the folio also.
2966 	 *
2967 	 * private_lock must be held over this entire operation in order
2968 	 * to synchronise against block_dirty_folio and prevent the
2969 	 * dirty bit from being lost.
2970 	 */
2971 	if (ret)
2972 		folio_cancel_dirty(folio);
2973 	spin_unlock(&mapping->private_lock);
2974 out:
2975 	if (buffers_to_free) {
2976 		struct buffer_head *bh = buffers_to_free;
2977 
2978 		do {
2979 			struct buffer_head *next = bh->b_this_page;
2980 			free_buffer_head(bh);
2981 			bh = next;
2982 		} while (bh != buffers_to_free);
2983 	}
2984 	return ret;
2985 }
2986 EXPORT_SYMBOL(try_to_free_buffers);
2987 
2988 /*
2989  * Buffer-head allocation
2990  */
2991 static struct kmem_cache *bh_cachep __read_mostly;
2992 
2993 /*
2994  * Once the number of bh's in the machine exceeds this level, we start
2995  * stripping them in writeback.
2996  */
2997 static unsigned long max_buffer_heads;
2998 
2999 int buffer_heads_over_limit;
3000 
3001 struct bh_accounting {
3002 	int nr;			/* Number of live bh's */
3003 	int ratelimit;		/* Limit cacheline bouncing */
3004 };
3005 
3006 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3007 
recalc_bh_state(void)3008 static void recalc_bh_state(void)
3009 {
3010 	int i;
3011 	int tot = 0;
3012 
3013 	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3014 		return;
3015 	__this_cpu_write(bh_accounting.ratelimit, 0);
3016 	for_each_online_cpu(i)
3017 		tot += per_cpu(bh_accounting, i).nr;
3018 	buffer_heads_over_limit = (tot > max_buffer_heads);
3019 }
3020 
alloc_buffer_head(gfp_t gfp_flags)3021 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3022 {
3023 	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3024 	if (ret) {
3025 		INIT_LIST_HEAD(&ret->b_assoc_buffers);
3026 		spin_lock_init(&ret->b_uptodate_lock);
3027 		preempt_disable();
3028 		__this_cpu_inc(bh_accounting.nr);
3029 		recalc_bh_state();
3030 		preempt_enable();
3031 	}
3032 	return ret;
3033 }
3034 EXPORT_SYMBOL(alloc_buffer_head);
3035 
free_buffer_head(struct buffer_head * bh)3036 void free_buffer_head(struct buffer_head *bh)
3037 {
3038 	BUG_ON(!list_empty(&bh->b_assoc_buffers));
3039 	kmem_cache_free(bh_cachep, bh);
3040 	preempt_disable();
3041 	__this_cpu_dec(bh_accounting.nr);
3042 	recalc_bh_state();
3043 	preempt_enable();
3044 }
3045 EXPORT_SYMBOL(free_buffer_head);
3046 
buffer_exit_cpu_dead(unsigned int cpu)3047 static int buffer_exit_cpu_dead(unsigned int cpu)
3048 {
3049 	int i;
3050 	struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3051 
3052 	for (i = 0; i < BH_LRU_SIZE; i++) {
3053 		brelse(b->bhs[i]);
3054 		b->bhs[i] = NULL;
3055 	}
3056 	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3057 	per_cpu(bh_accounting, cpu).nr = 0;
3058 	return 0;
3059 }
3060 
3061 /**
3062  * bh_uptodate_or_lock - Test whether the buffer is uptodate
3063  * @bh: struct buffer_head
3064  *
3065  * Return true if the buffer is up-to-date and false,
3066  * with the buffer locked, if not.
3067  */
bh_uptodate_or_lock(struct buffer_head * bh)3068 int bh_uptodate_or_lock(struct buffer_head *bh)
3069 {
3070 	if (!buffer_uptodate(bh)) {
3071 		lock_buffer(bh);
3072 		if (!buffer_uptodate(bh))
3073 			return 0;
3074 		unlock_buffer(bh);
3075 	}
3076 	return 1;
3077 }
3078 EXPORT_SYMBOL(bh_uptodate_or_lock);
3079 
3080 /**
3081  * __bh_read - Submit read for a locked buffer
3082  * @bh: struct buffer_head
3083  * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3084  * @wait: wait until reading finish
3085  *
3086  * Returns zero on success or don't wait, and -EIO on error.
3087  */
__bh_read(struct buffer_head * bh,blk_opf_t op_flags,bool wait)3088 int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait)
3089 {
3090 	int ret = 0;
3091 
3092 	BUG_ON(!buffer_locked(bh));
3093 
3094 	get_bh(bh);
3095 	bh->b_end_io = end_buffer_read_sync;
3096 	submit_bh(REQ_OP_READ | op_flags, bh);
3097 	if (wait) {
3098 		wait_on_buffer(bh);
3099 		if (!buffer_uptodate(bh))
3100 			ret = -EIO;
3101 	}
3102 	return ret;
3103 }
3104 EXPORT_SYMBOL(__bh_read);
3105 
3106 /**
3107  * __bh_read_batch - Submit read for a batch of unlocked buffers
3108  * @nr: entry number of the buffer batch
3109  * @bhs: a batch of struct buffer_head
3110  * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3111  * @force_lock: force to get a lock on the buffer if set, otherwise drops any
3112  *              buffer that cannot lock.
3113  *
3114  * Returns zero on success or don't wait, and -EIO on error.
3115  */
__bh_read_batch(int nr,struct buffer_head * bhs[],blk_opf_t op_flags,bool force_lock)3116 void __bh_read_batch(int nr, struct buffer_head *bhs[],
3117 		     blk_opf_t op_flags, bool force_lock)
3118 {
3119 	int i;
3120 
3121 	for (i = 0; i < nr; i++) {
3122 		struct buffer_head *bh = bhs[i];
3123 
3124 		if (buffer_uptodate(bh))
3125 			continue;
3126 
3127 		if (force_lock)
3128 			lock_buffer(bh);
3129 		else
3130 			if (!trylock_buffer(bh))
3131 				continue;
3132 
3133 		if (buffer_uptodate(bh)) {
3134 			unlock_buffer(bh);
3135 			continue;
3136 		}
3137 
3138 		bh->b_end_io = end_buffer_read_sync;
3139 		get_bh(bh);
3140 		submit_bh(REQ_OP_READ | op_flags, bh);
3141 	}
3142 }
3143 EXPORT_SYMBOL(__bh_read_batch);
3144 
buffer_init(void)3145 void __init buffer_init(void)
3146 {
3147 	unsigned long nrpages;
3148 	int ret;
3149 
3150 	bh_cachep = kmem_cache_create("buffer_head",
3151 			sizeof(struct buffer_head), 0,
3152 				(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3153 				SLAB_MEM_SPREAD),
3154 				NULL);
3155 
3156 	/*
3157 	 * Limit the bh occupancy to 10% of ZONE_NORMAL
3158 	 */
3159 	nrpages = (nr_free_buffer_pages() * 10) / 100;
3160 	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3161 	ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3162 					NULL, buffer_exit_cpu_dead);
3163 	WARN_ON(ret < 0);
3164 }
3165