summaryrefslogtreecommitdiff
path: root/include/linux/buffer_head.h
blob: 5f23ee599889fe3a87e519e440283ca07e1f97b8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
/* SPDX-License-Identifier: GPL-2.0 */
/*
 * include/linux/buffer_head.h
 *
 * Everything to do with buffer_heads.
 */

#ifndef _LINUX_BUFFER_HEAD_H
#define _LINUX_BUFFER_HEAD_H

#include <linux/types.h>
#include <linux/blk_types.h>
#include <linux/fs.h>
#include <linux/linkage.h>
#include <linux/pagemap.h>
#include <linux/wait.h>
#include <linux/atomic.h>

enum bh_state_bits {
	BH_Uptodate,	/* Contains valid data */
	BH_Dirty,	/* Is dirty */
	BH_Lock,	/* Is locked */
	BH_Req,		/* Has been submitted for I/O */

	BH_Mapped,	/* Has a disk mapping */
	BH_New,		/* Disk mapping was newly created by get_block */
	BH_Async_Read,	/* Is under end_buffer_async_read I/O */
	BH_Async_Write,	/* Is under end_buffer_async_write I/O */
	BH_Delay,	/* Buffer is not yet allocated on disk */
	BH_Boundary,	/* Block is followed by a discontiguity */
	BH_Write_EIO,	/* I/O error on write */
	BH_Unwritten,	/* Buffer is allocated on disk but not written */
	BH_Quiet,	/* Buffer Error Prinks to be quiet */
	BH_Meta,	/* Buffer contains metadata */
	BH_Prio,	/* Buffer should be submitted with REQ_PRIO */
	BH_Defer_Completion, /* Defer AIO completion to workqueue */

	BH_PrivateStart,/* not a state bit, but the first bit available
			 * for private allocation by other entities
			 */
};

#define MAX_BUF_PER_PAGE (PAGE_SIZE / 512)

struct page;
struct buffer_head;
struct address_space;
typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);

/*
 * Historically, a buffer_head was used to map a single block
 * within a page, and of course as the unit of I/O through the
 * filesystem and block layers.  Nowadays the basic I/O unit
 * is the bio, and buffer_heads are used for extracting block
 * mappings (via a get_block_t call), for tracking state within
 * a page (via a page_mapping) and for wrapping bio submission
 * for backward compatibility reasons (e.g. submit_bh).
 */
struct buffer_head {
	unsigned long b_state;		/* buffer state bitmap (see above) */
	struct buffer_head *b_this_page;/* circular list of page's buffers */
	union {
		struct page *b_page;	/* the page this bh is mapped to */
		struct folio *b_folio;	/* the folio this bh is mapped to */
	};

	sector_t b_blocknr;		/* start block number */
	size_t b_size;			/* size of mapping */
	char *b_data;			/* pointer to data within the page */

	struct block_device *b_bdev;
	bh_end_io_t *b_end_io;		/* I/O completion */
 	void *b_private;		/* reserved for b_end_io */
	struct list_head b_assoc_buffers; /* associated with another mapping */
	struct address_space *b_assoc_map;	/* mapping this buffer is
						   associated with */
	atomic_t b_count;		/* users using this buffer_head */
	spinlock_t b_uptodate_lock;	/* Used by the first bh in a page, to
					 * serialise IO completion of other
					 * buffers in the page */
};

/*
 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
 * and buffer_foo() functions.
 * To avoid reset buffer flags that are already set, because that causes
 * a costly cache line transition, check the flag first.
 */
#define BUFFER_FNS(bit, name)						\
static __always_inline void set_buffer_##name(struct buffer_head *bh)	\
{									\
	if (!test_bit(BH_##bit, &(bh)->b_state))			\
		set_bit(BH_##bit, &(bh)->b_state);			\
}									\
static __always_inline void clear_buffer_##name(struct buffer_head *bh)	\
{									\
	clear_bit(BH_##bit, &(bh)->b_state);				\
}									\
static __always_inline int buffer_##name(const struct buffer_head *bh)	\
{									\
	return test_bit(BH_##bit, &(bh)->b_state);			\
}

/*
 * test_set_buffer_foo() and test_clear_buffer_foo()
 */
#define TAS_BUFFER_FNS(bit, name)					\
static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
{									\
	return test_and_set_bit(BH_##bit, &(bh)->b_state);		\
}									\
static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \
{									\
	return test_and_clear_bit(BH_##bit, &(bh)->b_state);		\
}									\

/*
 * Emit the buffer bitops functions.   Note that there are also functions
 * of the form "mark_buffer_foo()".  These are higher-level functions which
 * do something in addition to setting a b_state bit.
 */
BUFFER_FNS(Dirty, dirty)
TAS_BUFFER_FNS(Dirty, dirty)
BUFFER_FNS(Lock, locked)
BUFFER_FNS(Req, req)
TAS_BUFFER_FNS(Req, req)
BUFFER_FNS(Mapped, mapped)
BUFFER_FNS(New, new)
BUFFER_FNS(Async_Read, async_read)
BUFFER_FNS(Async_Write, async_write)
BUFFER_FNS(Delay, delay)
BUFFER_FNS(Boundary, boundary)
BUFFER_FNS(Write_EIO, write_io_error)
BUFFER_FNS(Unwritten, unwritten)
BUFFER_FNS(Meta, meta)
BUFFER_FNS(Prio, prio)
BUFFER_FNS(Defer_Completion, defer_completion)

static __always_inline void set_buffer_uptodate(struct buffer_head *bh)
{
	/*
	 * If somebody else already set this uptodate, they will
	 * have done the memory barrier, and a reader will thus
	 * see *some* valid buffer state.
	 *
	 * Any other serialization (with IO errors or whatever that
	 * might clear the bit) has to come from other state (eg BH_Lock).
	 */
	if (test_bit(BH_Uptodate, &bh->b_state))
		return;

	/*
	 * make it consistent with folio_mark_uptodate
	 * pairs with smp_load_acquire in buffer_uptodate
	 */
	smp_mb__before_atomic();
	set_bit(BH_Uptodate, &bh->b_state);
}

static __always_inline void clear_buffer_uptodate(struct buffer_head *bh)
{
	clear_bit(BH_Uptodate, &bh->b_state);
}

static __always_inline int buffer_uptodate(const struct buffer_head *bh)
{
	/*
	 * make it consistent with folio_test_uptodate
	 * pairs with smp_mb__before_atomic in set_buffer_uptodate
	 */
	return test_bit_acquire(BH_Uptodate, &bh->b_state);
}

static inline unsigned long bh_offset(const struct buffer_head *bh)
{
	return (unsigned long)(bh)->b_data & (page_size(bh->b_page) - 1);
}

/* If we *know* page->private refers to buffer_heads */
#define page_buffers(page)					\
	({							\
		BUG_ON(!PagePrivate(page));			\
		((struct buffer_head *)page_private(page));	\
	})
#define page_has_buffers(page)	PagePrivate(page)
#define folio_buffers(folio)		folio_get_private(folio)

void buffer_check_dirty_writeback(struct folio *folio,
				     bool *dirty, bool *writeback);

/*
 * Declarations
 */

void mark_buffer_dirty(struct buffer_head *bh);
void mark_buffer_write_io_error(struct buffer_head *bh);
void touch_buffer(struct buffer_head *bh);
void folio_set_bh(struct buffer_head *bh, struct folio *folio,
		  unsigned long offset);
struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size,
					gfp_t gfp);
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
		bool retry);
struct buffer_head *create_empty_buffers(struct folio *folio,
		unsigned long blocksize, unsigned long b_state);
void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
void end_buffer_async_write(struct buffer_head *bh, int uptodate);

/* Things to do with buffers at mapping->private_list */
void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end,
				  bool datasync);
int generic_buffers_fsync(struct file *file, loff_t start, loff_t end,
			  bool datasync);
void clean_bdev_aliases(struct block_device *bdev, sector_t block,
			sector_t len);
static inline void clean_bdev_bh_alias(struct buffer_head *bh)
{
	clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
}

void mark_buffer_async_write(struct buffer_head *bh);
void __wait_on_buffer(struct buffer_head *);
wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
			unsigned size);
struct buffer_head *bdev_getblk(struct block_device *bdev, sector_t block,
		unsigned size, gfp_t gfp);
void __brelse(struct buffer_head *);
void __bforget(struct buffer_head *);
void __breadahead(struct block_device *, sector_t block, unsigned int size);
struct buffer_head *__bread_gfp(struct block_device *,
				sector_t block, unsigned size, gfp_t gfp);
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
void free_buffer_head(struct buffer_head * bh);
void unlock_buffer(struct buffer_head *bh);
void __lock_buffer(struct buffer_head *bh);
int sync_dirty_buffer(struct buffer_head *bh);
int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags);
void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags);
void submit_bh(blk_opf_t, struct buffer_head *);
void write_boundary_block(struct block_device *bdev,
			sector_t bblock, unsigned blocksize);
int bh_uptodate_or_lock(struct buffer_head *bh);
int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait);
void __bh_read_batch(int nr, struct buffer_head *bhs[],
		     blk_opf_t op_flags, bool force_lock);

/*
 * Generic address_space_operations implementations for buffer_head-backed
 * address_spaces.
 */
void block_invalidate_folio(struct folio *folio, size_t offset, size_t length);
int block_write_full_page(struct page *page, get_block_t *get_block,
				struct writeback_control *wbc);
int __block_write_full_folio(struct inode *inode, struct folio *folio,
			get_block_t *get_block, struct writeback_control *wbc,
			bh_end_io_t *handler);
int block_read_full_folio(struct folio *, get_block_t *);
bool block_is_partially_uptodate(struct folio *, size_t from, size_t count);
int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
		struct page **pagep, get_block_t *get_block);
int __block_write_begin(struct page *page, loff_t pos, unsigned len,
		get_block_t *get_block);
int block_write_end(struct file *, struct address_space *,
				loff_t, unsigned, unsigned,
				struct page *, void *);
int generic_write_end(struct file *, struct address_space *,
				loff_t, unsigned, unsigned,
				struct page *, void *);
void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to);
void clean_page_buffers(struct page *page);
int cont_write_begin(struct file *, struct address_space *, loff_t,
			unsigned, struct page **, void **,
			get_block_t *, loff_t *);
int generic_cont_expand_simple(struct inode *inode, loff_t size);
void block_commit_write(struct page *page, unsigned int from, unsigned int to);
int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
				get_block_t get_block);
sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
int block_truncate_page(struct address_space *, loff_t, get_block_t *);

#ifdef CONFIG_MIGRATION
extern int buffer_migrate_folio(struct address_space *,
		struct folio *dst, struct folio *src, enum migrate_mode);
extern int buffer_migrate_folio_norefs(struct address_space *,
		struct folio *dst, struct folio *src, enum migrate_mode);
#else
#define buffer_migrate_folio NULL
#define buffer_migrate_folio_norefs NULL
#endif

/*
 * inline definitions
 */

static inline void get_bh(struct buffer_head *bh)
{
        atomic_inc(&bh->b_count);
}

static inline void put_bh(struct buffer_head *bh)
{
        smp_mb__before_atomic();
        atomic_dec(&bh->b_count);
}

static inline void brelse(struct buffer_head *bh)
{
	if (bh)
		__brelse(bh);
}

static inline void bforget(struct buffer_head *bh)
{
	if (bh)
		__bforget(bh);
}

static inline struct buffer_head *
sb_bread(struct super_block *sb, sector_t block)
{
	return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
}

static inline struct buffer_head *
sb_bread_unmovable(struct super_block *sb, sector_t block)
{
	return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
}

static inline void
sb_breadahead(struct super_block *sb, sector_t block)
{
	__breadahead(sb->s_bdev, block, sb->s_blocksize);
}

static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
		sector_t block, unsigned size)
{
	gfp_t gfp;

	gfp = mapping_gfp_constraint(bdev->bd_inode->i_mapping, ~__GFP_FS);
	gfp |= __GFP_NOFAIL;

	return bdev_getblk(bdev, block, size, gfp);
}

static inline struct buffer_head *__getblk(struct block_device *bdev,
		sector_t block, unsigned size)
{
	gfp_t gfp;

	gfp = mapping_gfp_constraint(bdev->bd_inode->i_mapping, ~__GFP_FS);
	gfp |= __GFP_MOVABLE | __GFP_NOFAIL;

	return bdev_getblk(bdev, block, size, gfp);
}

static inline struct buffer_head *sb_getblk(struct super_block *sb,
		sector_t block)
{
	return __getblk(sb->s_bdev, block, sb->s_blocksize);
}

static inline struct buffer_head *sb_getblk_gfp(struct super_block *sb,
		sector_t block, gfp_t gfp)
{
	return bdev_getblk(sb->s_bdev, block, sb->s_blocksize, gfp);
}

static inline struct buffer_head *
sb_find_get_block(struct super_block *sb, sector_t block)
{
	return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
}

static inline void
map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
{
	set_buffer_mapped(bh);
	bh->b_bdev = sb->s_bdev;
	bh->b_blocknr = block;
	bh->b_size = sb->s_blocksize;
}

static inline void wait_on_buffer(struct buffer_head *bh)
{
	might_sleep();
	if (buffer_locked(bh))
		__wait_on_buffer(bh);
}

static inline int trylock_buffer(struct buffer_head *bh)
{
	return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
}

static inline void lock_buffer(struct buffer_head *bh)
{
	might_sleep();
	if (!trylock_buffer(bh))
		__lock_buffer(bh);
}

static inline void bh_readahead(struct buffer_head *bh, blk_opf_t op_flags)
{
	if (!buffer_uptodate(bh) && trylock_buffer(bh)) {
		if (!buffer_uptodate(bh))
			__bh_read(bh, op_flags, false);
		else
			unlock_buffer(bh);
	}
}

static inline void bh_read_nowait(struct buffer_head *bh, blk_opf_t op_flags)
{
	if (!bh_uptodate_or_lock(bh))
		__bh_read(bh, op_flags, false);
}

/* Returns 1 if buffer uptodated, 0 on success, and -EIO on error. */
static inline int bh_read(struct buffer_head *bh, blk_opf_t op_flags)
{
	if (bh_uptodate_or_lock(bh))
		return 1;
	return __bh_read(bh, op_flags, true);
}

static inline void bh_read_batch(int nr, struct buffer_head *bhs[])
{
	__bh_read_batch(nr, bhs, 0, true);
}

static inline void bh_readahead_batch(int nr, struct buffer_head *bhs[],
				      blk_opf_t op_flags)
{
	__bh_read_batch(nr, bhs, op_flags, false);
}

/**
 *  __bread() - reads a specified block and returns the bh
 *  @bdev: the block_device to read from
 *  @block: number of block
 *  @size: size (in bytes) to read
 *
 *  Reads a specified block, and returns buffer head that contains it.
 *  The page cache is allocated from movable area so that it can be migrated.
 *  It returns NULL if the block was unreadable.
 */
static inline struct buffer_head *
__bread(struct block_device *bdev, sector_t block, unsigned size)
{
	return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
}

/**
 * get_nth_bh - Get a reference on the n'th buffer after this one.
 * @bh: The buffer to start counting from.
 * @count: How many buffers to skip.
 *
 * This is primarily useful for finding the nth buffer in a folio; in
 * that case you pass the head buffer and the byte offset in the folio
 * divided by the block size.  It can be used for other purposes, but
 * it will wrap at the end of the folio rather than returning NULL or
 * proceeding to the next folio for you.
 *
 * Return: The requested buffer with an elevated refcount.
 */
static inline __must_check
struct buffer_head *get_nth_bh(struct buffer_head *bh, unsigned int count)
{
	while (count--)
		bh = bh->b_this_page;
	get_bh(bh);
	return bh;
}

bool block_dirty_folio(struct address_space *mapping, struct folio *folio);

#ifdef CONFIG_BUFFER_HEAD

void buffer_init(void);
bool try_to_free_buffers(struct folio *folio);
int inode_has_buffers(struct inode *inode);
void invalidate_inode_buffers(struct inode *inode);
int remove_inode_buffers(struct inode *inode);
int sync_mapping_buffers(struct address_space *mapping);
void invalidate_bh_lrus(void);
void invalidate_bh_lrus_cpu(void);
bool has_bh_in_lru(int cpu, void *dummy);
extern int buffer_heads_over_limit;

#else /* CONFIG_BUFFER_HEAD */

static inline void buffer_init(void) {}
static inline bool try_to_free_buffers(struct folio *folio) { return true; }
static inline int inode_has_buffers(struct inode *inode) { return 0; }
static inline void invalidate_inode_buffers(struct inode *inode) {}
static inline int remove_inode_buffers(struct inode *inode) { return 1; }
static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
static inline void invalidate_bh_lrus(void) {}
static inline void invalidate_bh_lrus_cpu(void) {}
static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; }
#define buffer_heads_over_limit 0

#endif /* CONFIG_BUFFER_HEAD */
#endif /* _LINUX_BUFFER_HEAD_H */