Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0 */
2 : /*
3 : * include/linux/buffer_head.h
4 : *
5 : * Everything to do with buffer_heads.
6 : */
7 :
8 : #ifndef _LINUX_BUFFER_HEAD_H
9 : #define _LINUX_BUFFER_HEAD_H
10 :
11 : #include <linux/types.h>
12 : #include <linux/blk_types.h>
13 : #include <linux/fs.h>
14 : #include <linux/linkage.h>
15 : #include <linux/pagemap.h>
16 : #include <linux/wait.h>
17 : #include <linux/atomic.h>
18 :
19 : #ifdef CONFIG_BLOCK
20 :
21 : enum bh_state_bits {
22 : BH_Uptodate, /* Contains valid data */
23 : BH_Dirty, /* Is dirty */
24 : BH_Lock, /* Is locked */
25 : BH_Req, /* Has been submitted for I/O */
26 :
27 : BH_Mapped, /* Has a disk mapping */
28 : BH_New, /* Disk mapping was newly created by get_block */
29 : BH_Async_Read, /* Is under end_buffer_async_read I/O */
30 : BH_Async_Write, /* Is under end_buffer_async_write I/O */
31 : BH_Delay, /* Buffer is not yet allocated on disk */
32 : BH_Boundary, /* Block is followed by a discontiguity */
33 : BH_Write_EIO, /* I/O error on write */
34 : BH_Unwritten, /* Buffer is allocated on disk but not written */
35 : BH_Quiet, /* Buffer Error Prinks to be quiet */
36 : BH_Meta, /* Buffer contains metadata */
37 : BH_Prio, /* Buffer should be submitted with REQ_PRIO */
38 : BH_Defer_Completion, /* Defer AIO completion to workqueue */
39 :
40 : BH_PrivateStart,/* not a state bit, but the first bit available
41 : * for private allocation by other entities
42 : */
43 : };
44 :
45 : #define MAX_BUF_PER_PAGE (PAGE_SIZE / 512)
46 :
47 : struct page;
48 : struct buffer_head;
49 : struct address_space;
50 : typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
51 :
52 : /*
53 : * Historically, a buffer_head was used to map a single block
54 : * within a page, and of course as the unit of I/O through the
55 : * filesystem and block layers. Nowadays the basic I/O unit
56 : * is the bio, and buffer_heads are used for extracting block
57 : * mappings (via a get_block_t call), for tracking state within
58 : * a page (via a page_mapping) and for wrapping bio submission
59 : * for backward compatibility reasons (e.g. submit_bh).
60 : */
61 : struct buffer_head {
62 : unsigned long b_state; /* buffer state bitmap (see above) */
63 : struct buffer_head *b_this_page;/* circular list of page's buffers */
64 : union {
65 : struct page *b_page; /* the page this bh is mapped to */
66 : struct folio *b_folio; /* the folio this bh is mapped to */
67 : };
68 :
69 : sector_t b_blocknr; /* start block number */
70 : size_t b_size; /* size of mapping */
71 : char *b_data; /* pointer to data within the page */
72 :
73 : struct block_device *b_bdev;
74 : bh_end_io_t *b_end_io; /* I/O completion */
75 : void *b_private; /* reserved for b_end_io */
76 : struct list_head b_assoc_buffers; /* associated with another mapping */
77 : struct address_space *b_assoc_map; /* mapping this buffer is
78 : associated with */
79 : atomic_t b_count; /* users using this buffer_head */
80 : spinlock_t b_uptodate_lock; /* Used by the first bh in a page, to
81 : * serialise IO completion of other
82 : * buffers in the page */
83 : };
84 :
85 : /*
86 : * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
87 : * and buffer_foo() functions.
88 : * To avoid reset buffer flags that are already set, because that causes
89 : * a costly cache line transition, check the flag first.
90 : */
91 : #define BUFFER_FNS(bit, name) \
92 : static __always_inline void set_buffer_##name(struct buffer_head *bh) \
93 : { \
94 : if (!test_bit(BH_##bit, &(bh)->b_state)) \
95 : set_bit(BH_##bit, &(bh)->b_state); \
96 : } \
97 : static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
98 : { \
99 : clear_bit(BH_##bit, &(bh)->b_state); \
100 : } \
101 : static __always_inline int buffer_##name(const struct buffer_head *bh) \
102 : { \
103 : return test_bit(BH_##bit, &(bh)->b_state); \
104 : }
105 :
106 : /*
107 : * test_set_buffer_foo() and test_clear_buffer_foo()
108 : */
109 : #define TAS_BUFFER_FNS(bit, name) \
110 : static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
111 : { \
112 : return test_and_set_bit(BH_##bit, &(bh)->b_state); \
113 : } \
114 : static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \
115 : { \
116 : return test_and_clear_bit(BH_##bit, &(bh)->b_state); \
117 : } \
118 :
119 : /*
120 : * Emit the buffer bitops functions. Note that there are also functions
121 : * of the form "mark_buffer_foo()". These are higher-level functions which
122 : * do something in addition to setting a b_state bit.
123 : */
124 0 : BUFFER_FNS(Dirty, dirty)
125 0 : TAS_BUFFER_FNS(Dirty, dirty)
126 0 : BUFFER_FNS(Lock, locked)
127 0 : BUFFER_FNS(Req, req)
128 0 : TAS_BUFFER_FNS(Req, req)
129 0 : BUFFER_FNS(Mapped, mapped)
130 0 : BUFFER_FNS(New, new)
131 0 : BUFFER_FNS(Async_Read, async_read)
132 0 : BUFFER_FNS(Async_Write, async_write)
133 0 : BUFFER_FNS(Delay, delay)
134 0 : BUFFER_FNS(Boundary, boundary)
135 0 : BUFFER_FNS(Write_EIO, write_io_error)
136 0 : BUFFER_FNS(Unwritten, unwritten)
137 0 : BUFFER_FNS(Meta, meta)
138 0 : BUFFER_FNS(Prio, prio)
139 : BUFFER_FNS(Defer_Completion, defer_completion)
140 :
141 : static __always_inline void set_buffer_uptodate(struct buffer_head *bh)
142 : {
143 : /*
144 : * If somebody else already set this uptodate, they will
145 : * have done the memory barrier, and a reader will thus
146 : * see *some* valid buffer state.
147 : *
148 : * Any other serialization (with IO errors or whatever that
149 : * might clear the bit) has to come from other state (eg BH_Lock).
150 : */
151 0 : if (test_bit(BH_Uptodate, &bh->b_state))
152 : return;
153 :
154 : /*
155 : * make it consistent with folio_mark_uptodate
156 : * pairs with smp_load_acquire in buffer_uptodate
157 : */
158 0 : smp_mb__before_atomic();
159 0 : set_bit(BH_Uptodate, &bh->b_state);
160 : }
161 :
162 : static __always_inline void clear_buffer_uptodate(struct buffer_head *bh)
163 : {
164 0 : clear_bit(BH_Uptodate, &bh->b_state);
165 : }
166 :
167 : static __always_inline int buffer_uptodate(const struct buffer_head *bh)
168 : {
169 : /*
170 : * make it consistent with folio_test_uptodate
171 : * pairs with smp_mb__before_atomic in set_buffer_uptodate
172 : */
173 0 : return test_bit_acquire(BH_Uptodate, &bh->b_state);
174 : }
175 :
176 : #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK)
177 :
178 : /* If we *know* page->private refers to buffer_heads */
179 : #define page_buffers(page) \
180 : ({ \
181 : BUG_ON(!PagePrivate(page)); \
182 : ((struct buffer_head *)page_private(page)); \
183 : })
184 : #define page_has_buffers(page) PagePrivate(page)
185 : #define folio_buffers(folio) folio_get_private(folio)
186 :
187 : void buffer_check_dirty_writeback(struct folio *folio,
188 : bool *dirty, bool *writeback);
189 :
190 : /*
191 : * Declarations
192 : */
193 :
194 : void mark_buffer_dirty(struct buffer_head *bh);
195 : void mark_buffer_write_io_error(struct buffer_head *bh);
196 : void touch_buffer(struct buffer_head *bh);
197 : void set_bh_page(struct buffer_head *bh,
198 : struct page *page, unsigned long offset);
199 : bool try_to_free_buffers(struct folio *);
200 : struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
201 : bool retry);
202 : void create_empty_buffers(struct page *, unsigned long,
203 : unsigned long b_state);
204 : void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
205 : void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
206 : void end_buffer_async_write(struct buffer_head *bh, int uptodate);
207 :
208 : /* Things to do with buffers at mapping->private_list */
209 : void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
210 : int inode_has_buffers(struct inode *);
211 : void invalidate_inode_buffers(struct inode *);
212 : int remove_inode_buffers(struct inode *inode);
213 : int sync_mapping_buffers(struct address_space *mapping);
214 : void clean_bdev_aliases(struct block_device *bdev, sector_t block,
215 : sector_t len);
216 : static inline void clean_bdev_bh_alias(struct buffer_head *bh)
217 : {
218 0 : clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
219 : }
220 :
221 : void mark_buffer_async_write(struct buffer_head *bh);
222 : void __wait_on_buffer(struct buffer_head *);
223 : wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
224 : struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
225 : unsigned size);
226 : struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
227 : unsigned size, gfp_t gfp);
228 : void __brelse(struct buffer_head *);
229 : void __bforget(struct buffer_head *);
230 : void __breadahead(struct block_device *, sector_t block, unsigned int size);
231 : struct buffer_head *__bread_gfp(struct block_device *,
232 : sector_t block, unsigned size, gfp_t gfp);
233 : void invalidate_bh_lrus(void);
234 : void invalidate_bh_lrus_cpu(void);
235 : bool has_bh_in_lru(int cpu, void *dummy);
236 : struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
237 : void free_buffer_head(struct buffer_head * bh);
238 : void unlock_buffer(struct buffer_head *bh);
239 : void __lock_buffer(struct buffer_head *bh);
240 : int sync_dirty_buffer(struct buffer_head *bh);
241 : int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags);
242 : void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags);
243 : void submit_bh(blk_opf_t, struct buffer_head *);
244 : void write_boundary_block(struct block_device *bdev,
245 : sector_t bblock, unsigned blocksize);
246 : int bh_uptodate_or_lock(struct buffer_head *bh);
247 : int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait);
248 : void __bh_read_batch(int nr, struct buffer_head *bhs[],
249 : blk_opf_t op_flags, bool force_lock);
250 :
251 : extern int buffer_heads_over_limit;
252 :
253 : /*
254 : * Generic address_space_operations implementations for buffer_head-backed
255 : * address_spaces.
256 : */
257 : void block_invalidate_folio(struct folio *folio, size_t offset, size_t length);
258 : int block_write_full_page(struct page *page, get_block_t *get_block,
259 : struct writeback_control *wbc);
260 : int __block_write_full_page(struct inode *inode, struct page *page,
261 : get_block_t *get_block, struct writeback_control *wbc,
262 : bh_end_io_t *handler);
263 : int block_read_full_folio(struct folio *, get_block_t *);
264 : bool block_is_partially_uptodate(struct folio *, size_t from, size_t count);
265 : int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
266 : struct page **pagep, get_block_t *get_block);
267 : int __block_write_begin(struct page *page, loff_t pos, unsigned len,
268 : get_block_t *get_block);
269 : int block_write_end(struct file *, struct address_space *,
270 : loff_t, unsigned, unsigned,
271 : struct page *, void *);
272 : int generic_write_end(struct file *, struct address_space *,
273 : loff_t, unsigned, unsigned,
274 : struct page *, void *);
275 : void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
276 : void clean_page_buffers(struct page *page);
277 : int cont_write_begin(struct file *, struct address_space *, loff_t,
278 : unsigned, struct page **, void **,
279 : get_block_t *, loff_t *);
280 : int generic_cont_expand_simple(struct inode *inode, loff_t size);
281 : int block_commit_write(struct page *page, unsigned from, unsigned to);
282 : int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
283 : get_block_t get_block);
284 : /* Convert errno to return value from ->page_mkwrite() call */
285 : static inline vm_fault_t block_page_mkwrite_return(int err)
286 : {
287 : if (err == 0)
288 : return VM_FAULT_LOCKED;
289 : if (err == -EFAULT || err == -EAGAIN)
290 : return VM_FAULT_NOPAGE;
291 : if (err == -ENOMEM)
292 : return VM_FAULT_OOM;
293 : /* -ENOSPC, -EDQUOT, -EIO ... */
294 : return VM_FAULT_SIGBUS;
295 : }
296 : sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
297 : int block_truncate_page(struct address_space *, loff_t, get_block_t *);
298 :
299 : #ifdef CONFIG_MIGRATION
300 : extern int buffer_migrate_folio(struct address_space *,
301 : struct folio *dst, struct folio *src, enum migrate_mode);
302 : extern int buffer_migrate_folio_norefs(struct address_space *,
303 : struct folio *dst, struct folio *src, enum migrate_mode);
304 : #else
305 : #define buffer_migrate_folio NULL
306 : #define buffer_migrate_folio_norefs NULL
307 : #endif
308 :
309 : void buffer_init(void);
310 :
311 : /*
312 : * inline definitions
313 : */
314 :
315 : static inline void get_bh(struct buffer_head *bh)
316 : {
317 0 : atomic_inc(&bh->b_count);
318 : }
319 :
320 : static inline void put_bh(struct buffer_head *bh)
321 : {
322 0 : smp_mb__before_atomic();
323 0 : atomic_dec(&bh->b_count);
324 : }
325 :
326 0 : static inline void brelse(struct buffer_head *bh)
327 : {
328 0 : if (bh)
329 : __brelse(bh);
330 0 : }
331 :
332 : static inline void bforget(struct buffer_head *bh)
333 : {
334 : if (bh)
335 : __bforget(bh);
336 : }
337 :
338 : static inline struct buffer_head *
339 : sb_bread(struct super_block *sb, sector_t block)
340 : {
341 : return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
342 : }
343 :
344 : static inline struct buffer_head *
345 : sb_bread_unmovable(struct super_block *sb, sector_t block)
346 : {
347 : return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
348 : }
349 :
350 : static inline void
351 : sb_breadahead(struct super_block *sb, sector_t block)
352 : {
353 : __breadahead(sb->s_bdev, block, sb->s_blocksize);
354 : }
355 :
356 : static inline struct buffer_head *
357 : sb_getblk(struct super_block *sb, sector_t block)
358 : {
359 : return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
360 : }
361 :
362 :
363 : static inline struct buffer_head *
364 : sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
365 : {
366 : return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
367 : }
368 :
369 : static inline struct buffer_head *
370 : sb_find_get_block(struct super_block *sb, sector_t block)
371 : {
372 : return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
373 : }
374 :
375 : static inline void
376 : map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
377 : {
378 : set_buffer_mapped(bh);
379 : bh->b_bdev = sb->s_bdev;
380 : bh->b_blocknr = block;
381 : bh->b_size = sb->s_blocksize;
382 : }
383 :
384 0 : static inline void wait_on_buffer(struct buffer_head *bh)
385 : {
386 : might_sleep();
387 0 : if (buffer_locked(bh))
388 : __wait_on_buffer(bh);
389 0 : }
390 :
391 : static inline int trylock_buffer(struct buffer_head *bh)
392 : {
393 0 : return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
394 : }
395 :
396 : static inline void lock_buffer(struct buffer_head *bh)
397 : {
398 : might_sleep();
399 0 : if (!trylock_buffer(bh))
400 0 : __lock_buffer(bh);
401 : }
402 :
403 : static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
404 : sector_t block,
405 : unsigned size)
406 : {
407 : return __getblk_gfp(bdev, block, size, 0);
408 : }
409 :
410 : static inline struct buffer_head *__getblk(struct block_device *bdev,
411 : sector_t block,
412 : unsigned size)
413 : {
414 0 : return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
415 : }
416 :
417 0 : static inline void bh_readahead(struct buffer_head *bh, blk_opf_t op_flags)
418 : {
419 0 : if (!buffer_uptodate(bh) && trylock_buffer(bh)) {
420 0 : if (!buffer_uptodate(bh))
421 0 : __bh_read(bh, op_flags, false);
422 : else
423 : unlock_buffer(bh);
424 : }
425 0 : }
426 :
427 0 : static inline void bh_read_nowait(struct buffer_head *bh, blk_opf_t op_flags)
428 : {
429 0 : if (!bh_uptodate_or_lock(bh))
430 0 : __bh_read(bh, op_flags, false);
431 0 : }
432 :
433 : /* Returns 1 if buffer uptodated, 0 on success, and -EIO on error. */
434 0 : static inline int bh_read(struct buffer_head *bh, blk_opf_t op_flags)
435 : {
436 0 : if (bh_uptodate_or_lock(bh))
437 : return 1;
438 0 : return __bh_read(bh, op_flags, true);
439 : }
440 :
441 : static inline void bh_read_batch(int nr, struct buffer_head *bhs[])
442 : {
443 : __bh_read_batch(nr, bhs, 0, true);
444 : }
445 :
446 : static inline void bh_readahead_batch(int nr, struct buffer_head *bhs[],
447 : blk_opf_t op_flags)
448 : {
449 : __bh_read_batch(nr, bhs, op_flags, false);
450 : }
451 :
452 : /**
453 : * __bread() - reads a specified block and returns the bh
454 : * @bdev: the block_device to read from
455 : * @block: number of block
456 : * @size: size (in bytes) to read
457 : *
458 : * Reads a specified block, and returns buffer head that contains it.
459 : * The page cache is allocated from movable area so that it can be migrated.
460 : * It returns NULL if the block was unreadable.
461 : */
462 : static inline struct buffer_head *
463 : __bread(struct block_device *bdev, sector_t block, unsigned size)
464 : {
465 : return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
466 : }
467 :
468 : bool block_dirty_folio(struct address_space *mapping, struct folio *folio);
469 :
470 : #else /* CONFIG_BLOCK */
471 :
472 : static inline void buffer_init(void) {}
473 : static inline bool try_to_free_buffers(struct folio *folio) { return true; }
474 : static inline int inode_has_buffers(struct inode *inode) { return 0; }
475 : static inline void invalidate_inode_buffers(struct inode *inode) {}
476 : static inline int remove_inode_buffers(struct inode *inode) { return 1; }
477 : static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
478 : static inline void invalidate_bh_lrus_cpu(void) {}
479 : static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; }
480 : #define buffer_heads_over_limit 0
481 :
482 : #endif /* CONFIG_BLOCK */
483 : #endif /* _LINUX_BUFFER_HEAD_H */
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