Commit | Line | Data |
---|---|---|
b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
1da177e4 LT |
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> | |
3ae72869 | 12 | #include <linux/blk_types.h> |
1da177e4 LT |
13 | #include <linux/fs.h> |
14 | #include <linux/linkage.h> | |
15 | #include <linux/pagemap.h> | |
16 | #include <linux/wait.h> | |
60063497 | 17 | #include <linux/atomic.h> |
1da177e4 LT |
18 | |
19 | enum bh_state_bits { | |
20 | BH_Uptodate, /* Contains valid data */ | |
21 | BH_Dirty, /* Is dirty */ | |
22 | BH_Lock, /* Is locked */ | |
23 | BH_Req, /* Has been submitted for I/O */ | |
24 | ||
25 | BH_Mapped, /* Has a disk mapping */ | |
26 | BH_New, /* Disk mapping was newly created by get_block */ | |
27 | BH_Async_Read, /* Is under end_buffer_async_read I/O */ | |
28 | BH_Async_Write, /* Is under end_buffer_async_write I/O */ | |
29 | BH_Delay, /* Buffer is not yet allocated on disk */ | |
30 | BH_Boundary, /* Block is followed by a discontiguity */ | |
31 | BH_Write_EIO, /* I/O error on write */ | |
33a266dd | 32 | BH_Unwritten, /* Buffer is allocated on disk but not written */ |
08bafc03 | 33 | BH_Quiet, /* Buffer Error Prinks to be quiet */ |
877f962c TT |
34 | BH_Meta, /* Buffer contains metadata */ |
35 | BH_Prio, /* Buffer should be submitted with REQ_PRIO */ | |
7b7a8665 | 36 | BH_Defer_Completion, /* Defer AIO completion to workqueue */ |
1da177e4 LT |
37 | |
38 | BH_PrivateStart,/* not a state bit, but the first bit available | |
39 | * for private allocation by other entities | |
40 | */ | |
41 | }; | |
42 | ||
09cbfeaf | 43 | #define MAX_BUF_PER_PAGE (PAGE_SIZE / 512) |
1da177e4 LT |
44 | |
45 | struct page; | |
46 | struct buffer_head; | |
47 | struct address_space; | |
48 | typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate); | |
49 | ||
50 | /* | |
205f87f6 BP |
51 | * Historically, a buffer_head was used to map a single block |
52 | * within a page, and of course as the unit of I/O through the | |
53 | * filesystem and block layers. Nowadays the basic I/O unit | |
54 | * is the bio, and buffer_heads are used for extracting block | |
55 | * mappings (via a get_block_t call), for tracking state within | |
56 | * a page (via a page_mapping) and for wrapping bio submission | |
57 | * for backward compatibility reasons (e.g. submit_bh). | |
1da177e4 LT |
58 | */ |
59 | struct buffer_head { | |
1da177e4 LT |
60 | unsigned long b_state; /* buffer state bitmap (see above) */ |
61 | struct buffer_head *b_this_page;/* circular list of page's buffers */ | |
d685c668 MWO |
62 | union { |
63 | struct page *b_page; /* the page this bh is mapped to */ | |
64 | struct folio *b_folio; /* the folio this bh is mapped to */ | |
65 | }; | |
1da177e4 | 66 | |
205f87f6 BP |
67 | sector_t b_blocknr; /* start block number */ |
68 | size_t b_size; /* size of mapping */ | |
69 | char *b_data; /* pointer to data within the page */ | |
1da177e4 LT |
70 | |
71 | struct block_device *b_bdev; | |
72 | bh_end_io_t *b_end_io; /* I/O completion */ | |
73 | void *b_private; /* reserved for b_end_io */ | |
74 | struct list_head b_assoc_buffers; /* associated with another mapping */ | |
58ff407b JK |
75 | struct address_space *b_assoc_map; /* mapping this buffer is |
76 | associated with */ | |
205f87f6 | 77 | atomic_t b_count; /* users using this buffer_head */ |
f1e67e35 TG |
78 | spinlock_t b_uptodate_lock; /* Used by the first bh in a page, to |
79 | * serialise IO completion of other | |
80 | * buffers in the page */ | |
1da177e4 LT |
81 | }; |
82 | ||
83 | /* | |
84 | * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() | |
85 | * and buffer_foo() functions. | |
60f91826 KW |
86 | * To avoid reset buffer flags that are already set, because that causes |
87 | * a costly cache line transition, check the flag first. | |
1da177e4 LT |
88 | */ |
89 | #define BUFFER_FNS(bit, name) \ | |
ee91ef61 | 90 | static __always_inline void set_buffer_##name(struct buffer_head *bh) \ |
1da177e4 | 91 | { \ |
60f91826 KW |
92 | if (!test_bit(BH_##bit, &(bh)->b_state)) \ |
93 | set_bit(BH_##bit, &(bh)->b_state); \ | |
1da177e4 | 94 | } \ |
ee91ef61 | 95 | static __always_inline void clear_buffer_##name(struct buffer_head *bh) \ |
1da177e4 LT |
96 | { \ |
97 | clear_bit(BH_##bit, &(bh)->b_state); \ | |
98 | } \ | |
ee91ef61 | 99 | static __always_inline int buffer_##name(const struct buffer_head *bh) \ |
1da177e4 LT |
100 | { \ |
101 | return test_bit(BH_##bit, &(bh)->b_state); \ | |
102 | } | |
103 | ||
104 | /* | |
105 | * test_set_buffer_foo() and test_clear_buffer_foo() | |
106 | */ | |
107 | #define TAS_BUFFER_FNS(bit, name) \ | |
ee91ef61 | 108 | static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \ |
1da177e4 LT |
109 | { \ |
110 | return test_and_set_bit(BH_##bit, &(bh)->b_state); \ | |
111 | } \ | |
ee91ef61 | 112 | static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \ |
1da177e4 LT |
113 | { \ |
114 | return test_and_clear_bit(BH_##bit, &(bh)->b_state); \ | |
115 | } \ | |
116 | ||
117 | /* | |
118 | * Emit the buffer bitops functions. Note that there are also functions | |
119 | * of the form "mark_buffer_foo()". These are higher-level functions which | |
120 | * do something in addition to setting a b_state bit. | |
121 | */ | |
1da177e4 LT |
122 | BUFFER_FNS(Dirty, dirty) |
123 | TAS_BUFFER_FNS(Dirty, dirty) | |
124 | BUFFER_FNS(Lock, locked) | |
1da177e4 LT |
125 | BUFFER_FNS(Req, req) |
126 | TAS_BUFFER_FNS(Req, req) | |
127 | BUFFER_FNS(Mapped, mapped) | |
128 | BUFFER_FNS(New, new) | |
129 | BUFFER_FNS(Async_Read, async_read) | |
130 | BUFFER_FNS(Async_Write, async_write) | |
131 | BUFFER_FNS(Delay, delay) | |
132 | BUFFER_FNS(Boundary, boundary) | |
133 | BUFFER_FNS(Write_EIO, write_io_error) | |
33a266dd | 134 | BUFFER_FNS(Unwritten, unwritten) |
877f962c TT |
135 | BUFFER_FNS(Meta, meta) |
136 | BUFFER_FNS(Prio, prio) | |
7b7a8665 | 137 | BUFFER_FNS(Defer_Completion, defer_completion) |
1da177e4 | 138 | |
d4252071 MP |
139 | static __always_inline void set_buffer_uptodate(struct buffer_head *bh) |
140 | { | |
2f79cdfe LT |
141 | /* |
142 | * If somebody else already set this uptodate, they will | |
143 | * have done the memory barrier, and a reader will thus | |
144 | * see *some* valid buffer state. | |
145 | * | |
146 | * Any other serialization (with IO errors or whatever that | |
147 | * might clear the bit) has to come from other state (eg BH_Lock). | |
148 | */ | |
149 | if (test_bit(BH_Uptodate, &bh->b_state)) | |
150 | return; | |
151 | ||
d4252071 MP |
152 | /* |
153 | * make it consistent with folio_mark_uptodate | |
154 | * pairs with smp_load_acquire in buffer_uptodate | |
155 | */ | |
156 | smp_mb__before_atomic(); | |
157 | set_bit(BH_Uptodate, &bh->b_state); | |
158 | } | |
159 | ||
160 | static __always_inline void clear_buffer_uptodate(struct buffer_head *bh) | |
161 | { | |
162 | clear_bit(BH_Uptodate, &bh->b_state); | |
163 | } | |
164 | ||
165 | static __always_inline int buffer_uptodate(const struct buffer_head *bh) | |
166 | { | |
167 | /* | |
168 | * make it consistent with folio_test_uptodate | |
169 | * pairs with smp_mb__before_atomic in set_buffer_uptodate | |
170 | */ | |
8238b457 | 171 | return test_bit_acquire(BH_Uptodate, &bh->b_state); |
d4252071 MP |
172 | } |
173 | ||
f94cf220 MWO |
174 | static inline unsigned long bh_offset(const struct buffer_head *bh) |
175 | { | |
176 | return (unsigned long)(bh)->b_data & (page_size(bh->b_page) - 1); | |
177 | } | |
1da177e4 LT |
178 | |
179 | /* If we *know* page->private refers to buffer_heads */ | |
180 | #define page_buffers(page) \ | |
181 | ({ \ | |
4c21e2f2 HD |
182 | BUG_ON(!PagePrivate(page)); \ |
183 | ((struct buffer_head *)page_private(page)); \ | |
1da177e4 LT |
184 | }) |
185 | #define page_has_buffers(page) PagePrivate(page) | |
cd1067be | 186 | #define folio_buffers(folio) folio_get_private(folio) |
1da177e4 | 187 | |
520f301c | 188 | void buffer_check_dirty_writeback(struct folio *folio, |
b4597226 MG |
189 | bool *dirty, bool *writeback); |
190 | ||
1da177e4 LT |
191 | /* |
192 | * Declarations | |
193 | */ | |
194 | ||
b3c97528 | 195 | void mark_buffer_dirty(struct buffer_head *bh); |
87354e5d | 196 | void mark_buffer_write_io_error(struct buffer_head *bh); |
f0059afd | 197 | void touch_buffer(struct buffer_head *bh); |
465e5e6a PR |
198 | void folio_set_bh(struct buffer_head *bh, struct folio *folio, |
199 | unsigned long offset); | |
c71124a8 | 200 | struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size, |
2a418157 | 201 | gfp_t gfp); |
1da177e4 | 202 | struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
640ab98f | 203 | bool retry); |
0a88810d | 204 | struct buffer_head *create_empty_buffers(struct folio *folio, |
3decb856 | 205 | unsigned long blocksize, unsigned long b_state); |
1da177e4 LT |
206 | void end_buffer_read_sync(struct buffer_head *bh, int uptodate); |
207 | void end_buffer_write_sync(struct buffer_head *bh, int uptodate); | |
1da177e4 LT |
208 | |
209 | /* Things to do with buffers at mapping->private_list */ | |
210 | void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); | |
31b2ebc0 RHI |
211 | int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end, |
212 | bool datasync); | |
213 | int generic_buffers_fsync(struct file *file, loff_t start, loff_t end, | |
214 | bool datasync); | |
29f3ad7d JK |
215 | void clean_bdev_aliases(struct block_device *bdev, sector_t block, |
216 | sector_t len); | |
e64855c6 JK |
217 | static inline void clean_bdev_bh_alias(struct buffer_head *bh) |
218 | { | |
219 | clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1); | |
220 | } | |
1da177e4 LT |
221 | |
222 | void mark_buffer_async_write(struct buffer_head *bh); | |
1da177e4 LT |
223 | void __wait_on_buffer(struct buffer_head *); |
224 | wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); | |
3991d3bd TK |
225 | struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, |
226 | unsigned size); | |
3ed65f04 MWO |
227 | struct buffer_head *bdev_getblk(struct block_device *bdev, sector_t block, |
228 | unsigned size, gfp_t gfp); | |
1da177e4 LT |
229 | void __brelse(struct buffer_head *); |
230 | void __bforget(struct buffer_head *); | |
3991d3bd | 231 | void __breadahead(struct block_device *, sector_t block, unsigned int size); |
3b5e6454 GK |
232 | struct buffer_head *__bread_gfp(struct block_device *, |
233 | sector_t block, unsigned size, gfp_t gfp); | |
dd0fc66f | 234 | struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); |
1da177e4 | 235 | void free_buffer_head(struct buffer_head * bh); |
b3c97528 HH |
236 | void unlock_buffer(struct buffer_head *bh); |
237 | void __lock_buffer(struct buffer_head *bh); | |
1da177e4 | 238 | int sync_dirty_buffer(struct buffer_head *bh); |
3ae72869 BVA |
239 | int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags); |
240 | void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags); | |
5bdf402a | 241 | void submit_bh(blk_opf_t, struct buffer_head *); |
1da177e4 LT |
242 | void write_boundary_block(struct block_device *bdev, |
243 | sector_t bblock, unsigned blocksize); | |
389d1b08 | 244 | int bh_uptodate_or_lock(struct buffer_head *bh); |
fdee117e ZY |
245 | int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait); |
246 | void __bh_read_batch(int nr, struct buffer_head *bhs[], | |
247 | blk_opf_t op_flags, bool force_lock); | |
1da177e4 | 248 | |
1da177e4 LT |
249 | /* |
250 | * Generic address_space_operations implementations for buffer_head-backed | |
251 | * address_spaces. | |
252 | */ | |
7ba13abb | 253 | void block_invalidate_folio(struct folio *folio, size_t offset, size_t length); |
17bf23a9 MWO |
254 | int block_write_full_folio(struct folio *folio, struct writeback_control *wbc, |
255 | void *get_block); | |
53418a18 | 256 | int __block_write_full_folio(struct inode *inode, struct folio *folio, |
14059f66 | 257 | get_block_t *get_block, struct writeback_control *wbc); |
2c69e205 | 258 | int block_read_full_folio(struct folio *, get_block_t *); |
2e7e80f7 | 259 | bool block_is_partially_uptodate(struct folio *, size_t from, size_t count); |
155130a4 | 260 | int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, |
b3992d1e | 261 | struct page **pagep, get_block_t *get_block); |
6e1db88d CH |
262 | int __block_write_begin(struct page *page, loff_t pos, unsigned len, |
263 | get_block_t *get_block); | |
afddba49 NP |
264 | int block_write_end(struct file *, struct address_space *, |
265 | loff_t, unsigned, unsigned, | |
266 | struct page *, void *); | |
267 | int generic_write_end(struct file *, struct address_space *, | |
268 | loff_t, unsigned, unsigned, | |
269 | struct page *, void *); | |
4a9622f2 | 270 | void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to); |
89e10787 | 271 | int cont_write_begin(struct file *, struct address_space *, loff_t, |
be3bbbc5 | 272 | unsigned, struct page **, void **, |
89e10787 | 273 | get_block_t *, loff_t *); |
05eb0b51 | 274 | int generic_cont_expand_simple(struct inode *inode, loff_t size); |
a524fcfe | 275 | void block_commit_write(struct page *page, unsigned int from, unsigned int to); |
c2ec175c | 276 | int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
54171690 | 277 | get_block_t get_block); |
1da177e4 | 278 | sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); |
1da177e4 | 279 | int block_truncate_page(struct address_space *, loff_t, get_block_t *); |
1da177e4 | 280 | |
67235182 MWO |
281 | #ifdef CONFIG_MIGRATION |
282 | extern int buffer_migrate_folio(struct address_space *, | |
283 | struct folio *dst, struct folio *src, enum migrate_mode); | |
284 | extern int buffer_migrate_folio_norefs(struct address_space *, | |
285 | struct folio *dst, struct folio *src, enum migrate_mode); | |
286 | #else | |
287 | #define buffer_migrate_folio NULL | |
288 | #define buffer_migrate_folio_norefs NULL | |
289 | #endif | |
1da177e4 | 290 | |
1da177e4 LT |
291 | /* |
292 | * inline definitions | |
293 | */ | |
294 | ||
1da177e4 LT |
295 | static inline void get_bh(struct buffer_head *bh) |
296 | { | |
297 | atomic_inc(&bh->b_count); | |
298 | } | |
299 | ||
300 | static inline void put_bh(struct buffer_head *bh) | |
301 | { | |
4e857c58 | 302 | smp_mb__before_atomic(); |
1da177e4 LT |
303 | atomic_dec(&bh->b_count); |
304 | } | |
305 | ||
306 | static inline void brelse(struct buffer_head *bh) | |
307 | { | |
308 | if (bh) | |
309 | __brelse(bh); | |
310 | } | |
311 | ||
312 | static inline void bforget(struct buffer_head *bh) | |
313 | { | |
314 | if (bh) | |
315 | __bforget(bh); | |
316 | } | |
317 | ||
318 | static inline struct buffer_head * | |
319 | sb_bread(struct super_block *sb, sector_t block) | |
320 | { | |
3b5e6454 GK |
321 | return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); |
322 | } | |
323 | ||
324 | static inline struct buffer_head * | |
325 | sb_bread_unmovable(struct super_block *sb, sector_t block) | |
326 | { | |
327 | return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0); | |
1da177e4 LT |
328 | } |
329 | ||
330 | static inline void | |
331 | sb_breadahead(struct super_block *sb, sector_t block) | |
332 | { | |
333 | __breadahead(sb->s_bdev, block, sb->s_blocksize); | |
334 | } | |
335 | ||
c645e65c MWO |
336 | static inline struct buffer_head *getblk_unmovable(struct block_device *bdev, |
337 | sector_t block, unsigned size) | |
338 | { | |
339 | gfp_t gfp; | |
340 | ||
341 | gfp = mapping_gfp_constraint(bdev->bd_inode->i_mapping, ~__GFP_FS); | |
342 | gfp |= __GFP_NOFAIL; | |
343 | ||
344 | return bdev_getblk(bdev, block, size, gfp); | |
345 | } | |
346 | ||
347 | static inline struct buffer_head *__getblk(struct block_device *bdev, | |
348 | sector_t block, unsigned size) | |
349 | { | |
350 | gfp_t gfp; | |
351 | ||
352 | gfp = mapping_gfp_constraint(bdev->bd_inode->i_mapping, ~__GFP_FS); | |
353 | gfp |= __GFP_MOVABLE | __GFP_NOFAIL; | |
354 | ||
355 | return bdev_getblk(bdev, block, size, gfp); | |
356 | } | |
357 | ||
4b9c8b19 MWO |
358 | static inline struct buffer_head *sb_getblk(struct super_block *sb, |
359 | sector_t block) | |
1da177e4 | 360 | { |
4b9c8b19 | 361 | return __getblk(sb->s_bdev, block, sb->s_blocksize); |
1da177e4 LT |
362 | } |
363 | ||
8a83ac54 MWO |
364 | static inline struct buffer_head *sb_getblk_gfp(struct super_block *sb, |
365 | sector_t block, gfp_t gfp) | |
bd7ade3c | 366 | { |
8a83ac54 | 367 | return bdev_getblk(sb->s_bdev, block, sb->s_blocksize, gfp); |
bd7ade3c NB |
368 | } |
369 | ||
1da177e4 LT |
370 | static inline struct buffer_head * |
371 | sb_find_get_block(struct super_block *sb, sector_t block) | |
372 | { | |
373 | return __find_get_block(sb->s_bdev, block, sb->s_blocksize); | |
374 | } | |
375 | ||
376 | static inline void | |
377 | map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) | |
378 | { | |
379 | set_buffer_mapped(bh); | |
380 | bh->b_bdev = sb->s_bdev; | |
381 | bh->b_blocknr = block; | |
b0cf2321 | 382 | bh->b_size = sb->s_blocksize; |
1da177e4 LT |
383 | } |
384 | ||
1da177e4 LT |
385 | static inline void wait_on_buffer(struct buffer_head *bh) |
386 | { | |
387 | might_sleep(); | |
a9877cc2 | 388 | if (buffer_locked(bh)) |
1da177e4 LT |
389 | __wait_on_buffer(bh); |
390 | } | |
391 | ||
ca5de404 NP |
392 | static inline int trylock_buffer(struct buffer_head *bh) |
393 | { | |
51b07fc3 | 394 | return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); |
ca5de404 NP |
395 | } |
396 | ||
1da177e4 LT |
397 | static inline void lock_buffer(struct buffer_head *bh) |
398 | { | |
399 | might_sleep(); | |
ca5de404 | 400 | if (!trylock_buffer(bh)) |
1da177e4 LT |
401 | __lock_buffer(bh); |
402 | } | |
403 | ||
fdee117e ZY |
404 | static inline void bh_readahead(struct buffer_head *bh, blk_opf_t op_flags) |
405 | { | |
406 | if (!buffer_uptodate(bh) && trylock_buffer(bh)) { | |
407 | if (!buffer_uptodate(bh)) | |
408 | __bh_read(bh, op_flags, false); | |
409 | else | |
410 | unlock_buffer(bh); | |
411 | } | |
412 | } | |
413 | ||
414 | static inline void bh_read_nowait(struct buffer_head *bh, blk_opf_t op_flags) | |
415 | { | |
416 | if (!bh_uptodate_or_lock(bh)) | |
417 | __bh_read(bh, op_flags, false); | |
418 | } | |
419 | ||
420 | /* Returns 1 if buffer uptodated, 0 on success, and -EIO on error. */ | |
421 | static inline int bh_read(struct buffer_head *bh, blk_opf_t op_flags) | |
422 | { | |
423 | if (bh_uptodate_or_lock(bh)) | |
424 | return 1; | |
425 | return __bh_read(bh, op_flags, true); | |
426 | } | |
427 | ||
428 | static inline void bh_read_batch(int nr, struct buffer_head *bhs[]) | |
429 | { | |
430 | __bh_read_batch(nr, bhs, 0, true); | |
431 | } | |
432 | ||
433 | static inline void bh_readahead_batch(int nr, struct buffer_head *bhs[], | |
434 | blk_opf_t op_flags) | |
435 | { | |
436 | __bh_read_batch(nr, bhs, op_flags, false); | |
437 | } | |
438 | ||
3b5e6454 GK |
439 | /** |
440 | * __bread() - reads a specified block and returns the bh | |
441 | * @bdev: the block_device to read from | |
442 | * @block: number of block | |
443 | * @size: size (in bytes) to read | |
444 | * | |
445 | * Reads a specified block, and returns buffer head that contains it. | |
446 | * The page cache is allocated from movable area so that it can be migrated. | |
447 | * It returns NULL if the block was unreadable. | |
448 | */ | |
449 | static inline struct buffer_head * | |
450 | __bread(struct block_device *bdev, sector_t block, unsigned size) | |
451 | { | |
452 | return __bread_gfp(bdev, block, size, __GFP_MOVABLE); | |
453 | } | |
454 | ||
0217fbb0 MWO |
455 | /** |
456 | * get_nth_bh - Get a reference on the n'th buffer after this one. | |
457 | * @bh: The buffer to start counting from. | |
458 | * @count: How many buffers to skip. | |
459 | * | |
460 | * This is primarily useful for finding the nth buffer in a folio; in | |
461 | * that case you pass the head buffer and the byte offset in the folio | |
462 | * divided by the block size. It can be used for other purposes, but | |
463 | * it will wrap at the end of the folio rather than returning NULL or | |
464 | * proceeding to the next folio for you. | |
465 | * | |
466 | * Return: The requested buffer with an elevated refcount. | |
467 | */ | |
468 | static inline __must_check | |
469 | struct buffer_head *get_nth_bh(struct buffer_head *bh, unsigned int count) | |
470 | { | |
471 | while (count--) | |
472 | bh = bh->b_this_page; | |
473 | get_bh(bh); | |
474 | return bh; | |
475 | } | |
476 | ||
e621900a | 477 | bool block_dirty_folio(struct address_space *mapping, struct folio *folio); |
9361401e | 478 | |
925c86a1 CH |
479 | #ifdef CONFIG_BUFFER_HEAD |
480 | ||
481 | void buffer_init(void); | |
482 | bool try_to_free_buffers(struct folio *folio); | |
483 | int inode_has_buffers(struct inode *inode); | |
484 | void invalidate_inode_buffers(struct inode *inode); | |
485 | int remove_inode_buffers(struct inode *inode); | |
486 | int sync_mapping_buffers(struct address_space *mapping); | |
487 | void invalidate_bh_lrus(void); | |
488 | void invalidate_bh_lrus_cpu(void); | |
489 | bool has_bh_in_lru(int cpu, void *dummy); | |
490 | extern int buffer_heads_over_limit; | |
491 | ||
492 | #else /* CONFIG_BUFFER_HEAD */ | |
9361401e DH |
493 | |
494 | static inline void buffer_init(void) {} | |
68189fef | 495 | static inline bool try_to_free_buffers(struct folio *folio) { return true; } |
9361401e DH |
496 | static inline int inode_has_buffers(struct inode *inode) { return 0; } |
497 | static inline void invalidate_inode_buffers(struct inode *inode) {} | |
498 | static inline int remove_inode_buffers(struct inode *inode) { return 1; } | |
499 | static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } | |
925c86a1 | 500 | static inline void invalidate_bh_lrus(void) {} |
243418e3 | 501 | static inline void invalidate_bh_lrus_cpu(void) {} |
6de522d1 | 502 | static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; } |
d2de7ea4 | 503 | #define buffer_heads_over_limit 0 |
9361401e | 504 | |
925c86a1 | 505 | #endif /* CONFIG_BUFFER_HEAD */ |
1da177e4 | 506 | #endif /* _LINUX_BUFFER_HEAD_H */ |