| 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 | 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 */ |
| 32 | BH_Unwritten, /* Buffer is allocated on disk but not written */ |
| 33 | BH_Quiet, /* Buffer Error Prinks to be quiet */ |
| 34 | BH_Meta, /* Buffer contains metadata */ |
| 35 | BH_Prio, /* Buffer should be submitted with REQ_PRIO */ |
| 36 | BH_Defer_Completion, /* Defer AIO completion to workqueue */ |
| 37 | |
| 38 | BH_PrivateStart,/* not a state bit, but the first bit available |
| 39 | * for private allocation by other entities |
| 40 | */ |
| 41 | }; |
| 42 | |
| 43 | #define MAX_BUF_PER_PAGE (PAGE_SIZE / 512) |
| 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 | /* |
| 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 folio (via a folio_mapping) and for wrapping bio submission |
| 57 | * for backward compatibility reasons (e.g. submit_bh). |
| 58 | */ |
| 59 | struct buffer_head { |
| 60 | unsigned long b_state; /* buffer state bitmap (see above) */ |
| 61 | struct buffer_head *b_this_page;/* circular list of page's buffers */ |
| 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 | }; |
| 66 | |
| 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 */ |
| 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 */ |
| 75 | struct address_space *b_assoc_map; /* mapping this buffer is |
| 76 | associated with */ |
| 77 | atomic_t b_count; /* users using this buffer_head */ |
| 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 */ |
| 81 | }; |
| 82 | |
| 83 | /* |
| 84 | * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() |
| 85 | * and buffer_foo() functions. |
| 86 | * To avoid reset buffer flags that are already set, because that causes |
| 87 | * a costly cache line transition, check the flag first. |
| 88 | */ |
| 89 | #define BUFFER_FNS(bit, name) \ |
| 90 | static __always_inline void set_buffer_##name(struct buffer_head *bh) \ |
| 91 | { \ |
| 92 | if (!test_bit(BH_##bit, &(bh)->b_state)) \ |
| 93 | set_bit(BH_##bit, &(bh)->b_state); \ |
| 94 | } \ |
| 95 | static __always_inline void clear_buffer_##name(struct buffer_head *bh) \ |
| 96 | { \ |
| 97 | clear_bit(BH_##bit, &(bh)->b_state); \ |
| 98 | } \ |
| 99 | static __always_inline int buffer_##name(const struct buffer_head *bh) \ |
| 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) \ |
| 108 | static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \ |
| 109 | { \ |
| 110 | return test_and_set_bit(BH_##bit, &(bh)->b_state); \ |
| 111 | } \ |
| 112 | static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \ |
| 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 | */ |
| 122 | BUFFER_FNS(Dirty, dirty) |
| 123 | TAS_BUFFER_FNS(Dirty, dirty) |
| 124 | BUFFER_FNS(Lock, locked) |
| 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) |
| 134 | BUFFER_FNS(Unwritten, unwritten) |
| 135 | BUFFER_FNS(Meta, meta) |
| 136 | BUFFER_FNS(Prio, prio) |
| 137 | BUFFER_FNS(Defer_Completion, defer_completion) |
| 138 | |
| 139 | static __always_inline void set_buffer_uptodate(struct buffer_head *bh) |
| 140 | { |
| 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 | |
| 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 | */ |
| 171 | return test_bit_acquire(BH_Uptodate, &bh->b_state); |
| 172 | } |
| 173 | |
| 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 | } |
| 178 | |
| 179 | /* If we *know* page->private refers to buffer_heads */ |
| 180 | #define page_buffers(page) \ |
| 181 | ({ \ |
| 182 | BUG_ON(!PagePrivate(page)); \ |
| 183 | ((struct buffer_head *)page_private(page)); \ |
| 184 | }) |
| 185 | #define page_has_buffers(page) PagePrivate(page) |
| 186 | #define folio_buffers(folio) folio_get_private(folio) |
| 187 | |
| 188 | void buffer_check_dirty_writeback(struct folio *folio, |
| 189 | bool *dirty, bool *writeback); |
| 190 | |
| 191 | /* |
| 192 | * Declarations |
| 193 | */ |
| 194 | |
| 195 | void mark_buffer_dirty(struct buffer_head *bh); |
| 196 | void mark_buffer_write_io_error(struct buffer_head *bh); |
| 197 | void touch_buffer(struct buffer_head *bh); |
| 198 | void folio_set_bh(struct buffer_head *bh, struct folio *folio, |
| 199 | unsigned long offset); |
| 200 | struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size, |
| 201 | gfp_t gfp); |
| 202 | struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
| 203 | bool retry); |
| 204 | struct buffer_head *create_empty_buffers(struct folio *folio, |
| 205 | unsigned long blocksize, unsigned long b_state); |
| 206 | void end_buffer_read_sync(struct buffer_head *bh, int uptodate); |
| 207 | void end_buffer_write_sync(struct buffer_head *bh, int uptodate); |
| 208 | |
| 209 | /* Things to do with buffers at mapping->private_list */ |
| 210 | void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); |
| 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); |
| 215 | void clean_bdev_aliases(struct block_device *bdev, sector_t block, |
| 216 | sector_t len); |
| 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 | } |
| 221 | |
| 222 | void mark_buffer_async_write(struct buffer_head *bh); |
| 223 | void __wait_on_buffer(struct buffer_head *); |
| 224 | wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); |
| 225 | struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, |
| 226 | unsigned size); |
| 227 | struct buffer_head *bdev_getblk(struct block_device *bdev, sector_t block, |
| 228 | unsigned size, gfp_t gfp); |
| 229 | void __brelse(struct buffer_head *); |
| 230 | void __bforget(struct buffer_head *); |
| 231 | void __breadahead(struct block_device *, sector_t block, unsigned int size); |
| 232 | struct buffer_head *__bread_gfp(struct block_device *, |
| 233 | sector_t block, unsigned size, gfp_t gfp); |
| 234 | struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); |
| 235 | void free_buffer_head(struct buffer_head * bh); |
| 236 | void unlock_buffer(struct buffer_head *bh); |
| 237 | void __lock_buffer(struct buffer_head *bh); |
| 238 | int sync_dirty_buffer(struct buffer_head *bh); |
| 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); |
| 241 | void submit_bh(blk_opf_t, struct buffer_head *); |
| 242 | void write_boundary_block(struct block_device *bdev, |
| 243 | sector_t bblock, unsigned blocksize); |
| 244 | int bh_uptodate_or_lock(struct buffer_head *bh); |
| 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); |
| 248 | |
| 249 | /* |
| 250 | * Generic address_space_operations implementations for buffer_head-backed |
| 251 | * address_spaces. |
| 252 | */ |
| 253 | void block_invalidate_folio(struct folio *folio, size_t offset, size_t length); |
| 254 | int block_write_full_folio(struct folio *folio, struct writeback_control *wbc, |
| 255 | void *get_block); |
| 256 | int __block_write_full_folio(struct inode *inode, struct folio *folio, |
| 257 | get_block_t *get_block, struct writeback_control *wbc); |
| 258 | int block_read_full_folio(struct folio *, get_block_t *); |
| 259 | bool block_is_partially_uptodate(struct folio *, size_t from, size_t count); |
| 260 | int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, |
| 261 | struct page **pagep, get_block_t *get_block); |
| 262 | int __block_write_begin(struct page *page, loff_t pos, unsigned len, |
| 263 | get_block_t *get_block); |
| 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 *); |
| 270 | void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to); |
| 271 | int cont_write_begin(struct file *, struct address_space *, loff_t, |
| 272 | unsigned, struct page **, void **, |
| 273 | get_block_t *, loff_t *); |
| 274 | int generic_cont_expand_simple(struct inode *inode, loff_t size); |
| 275 | void block_commit_write(struct page *page, unsigned int from, unsigned int to); |
| 276 | int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
| 277 | get_block_t get_block); |
| 278 | sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); |
| 279 | int block_truncate_page(struct address_space *, loff_t, get_block_t *); |
| 280 | |
| 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 |
| 290 | |
| 291 | /* |
| 292 | * inline definitions |
| 293 | */ |
| 294 | |
| 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 | { |
| 302 | smp_mb__before_atomic(); |
| 303 | atomic_dec(&bh->b_count); |
| 304 | } |
| 305 | |
| 306 | /** |
| 307 | * brelse - Release a buffer. |
| 308 | * @bh: The buffer to release. |
| 309 | * |
| 310 | * Decrement a buffer_head's reference count. If @bh is NULL, this |
| 311 | * function is a no-op. |
| 312 | * |
| 313 | * If all buffers on a folio have zero reference count, are clean |
| 314 | * and unlocked, and if the folio is unlocked and not under writeback |
| 315 | * then try_to_free_buffers() may strip the buffers from the folio in |
| 316 | * preparation for freeing it (sometimes, rarely, buffers are removed |
| 317 | * from a folio but it ends up not being freed, and buffers may later |
| 318 | * be reattached). |
| 319 | * |
| 320 | * Context: Any context. |
| 321 | */ |
| 322 | static inline void brelse(struct buffer_head *bh) |
| 323 | { |
| 324 | if (bh) |
| 325 | __brelse(bh); |
| 326 | } |
| 327 | |
| 328 | /** |
| 329 | * bforget - Discard any dirty data in a buffer. |
| 330 | * @bh: The buffer to forget. |
| 331 | * |
| 332 | * Call this function instead of brelse() if the data written to a buffer |
| 333 | * no longer needs to be written back. It will clear the buffer's dirty |
| 334 | * flag so writeback of this buffer will be skipped. |
| 335 | * |
| 336 | * Context: Any context. |
| 337 | */ |
| 338 | static inline void bforget(struct buffer_head *bh) |
| 339 | { |
| 340 | if (bh) |
| 341 | __bforget(bh); |
| 342 | } |
| 343 | |
| 344 | static inline struct buffer_head * |
| 345 | sb_bread(struct super_block *sb, sector_t block) |
| 346 | { |
| 347 | return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); |
| 348 | } |
| 349 | |
| 350 | static inline struct buffer_head * |
| 351 | sb_bread_unmovable(struct super_block *sb, sector_t block) |
| 352 | { |
| 353 | return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0); |
| 354 | } |
| 355 | |
| 356 | static inline void |
| 357 | sb_breadahead(struct super_block *sb, sector_t block) |
| 358 | { |
| 359 | __breadahead(sb->s_bdev, block, sb->s_blocksize); |
| 360 | } |
| 361 | |
| 362 | static inline struct buffer_head *getblk_unmovable(struct block_device *bdev, |
| 363 | sector_t block, unsigned size) |
| 364 | { |
| 365 | gfp_t gfp; |
| 366 | |
| 367 | gfp = mapping_gfp_constraint(bdev->bd_mapping, ~__GFP_FS); |
| 368 | gfp |= __GFP_NOFAIL; |
| 369 | |
| 370 | return bdev_getblk(bdev, block, size, gfp); |
| 371 | } |
| 372 | |
| 373 | static inline struct buffer_head *__getblk(struct block_device *bdev, |
| 374 | sector_t block, unsigned size) |
| 375 | { |
| 376 | gfp_t gfp; |
| 377 | |
| 378 | gfp = mapping_gfp_constraint(bdev->bd_mapping, ~__GFP_FS); |
| 379 | gfp |= __GFP_MOVABLE | __GFP_NOFAIL; |
| 380 | |
| 381 | return bdev_getblk(bdev, block, size, gfp); |
| 382 | } |
| 383 | |
| 384 | static inline struct buffer_head *sb_getblk(struct super_block *sb, |
| 385 | sector_t block) |
| 386 | { |
| 387 | return __getblk(sb->s_bdev, block, sb->s_blocksize); |
| 388 | } |
| 389 | |
| 390 | static inline struct buffer_head *sb_getblk_gfp(struct super_block *sb, |
| 391 | sector_t block, gfp_t gfp) |
| 392 | { |
| 393 | return bdev_getblk(sb->s_bdev, block, sb->s_blocksize, gfp); |
| 394 | } |
| 395 | |
| 396 | static inline struct buffer_head * |
| 397 | sb_find_get_block(struct super_block *sb, sector_t block) |
| 398 | { |
| 399 | return __find_get_block(sb->s_bdev, block, sb->s_blocksize); |
| 400 | } |
| 401 | |
| 402 | static inline void |
| 403 | map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) |
| 404 | { |
| 405 | set_buffer_mapped(bh); |
| 406 | bh->b_bdev = sb->s_bdev; |
| 407 | bh->b_blocknr = block; |
| 408 | bh->b_size = sb->s_blocksize; |
| 409 | } |
| 410 | |
| 411 | static inline void wait_on_buffer(struct buffer_head *bh) |
| 412 | { |
| 413 | might_sleep(); |
| 414 | if (buffer_locked(bh)) |
| 415 | __wait_on_buffer(bh); |
| 416 | } |
| 417 | |
| 418 | static inline int trylock_buffer(struct buffer_head *bh) |
| 419 | { |
| 420 | return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); |
| 421 | } |
| 422 | |
| 423 | static inline void lock_buffer(struct buffer_head *bh) |
| 424 | { |
| 425 | might_sleep(); |
| 426 | if (!trylock_buffer(bh)) |
| 427 | __lock_buffer(bh); |
| 428 | } |
| 429 | |
| 430 | static inline void bh_readahead(struct buffer_head *bh, blk_opf_t op_flags) |
| 431 | { |
| 432 | if (!buffer_uptodate(bh) && trylock_buffer(bh)) { |
| 433 | if (!buffer_uptodate(bh)) |
| 434 | __bh_read(bh, op_flags, false); |
| 435 | else |
| 436 | unlock_buffer(bh); |
| 437 | } |
| 438 | } |
| 439 | |
| 440 | static inline void bh_read_nowait(struct buffer_head *bh, blk_opf_t op_flags) |
| 441 | { |
| 442 | if (!bh_uptodate_or_lock(bh)) |
| 443 | __bh_read(bh, op_flags, false); |
| 444 | } |
| 445 | |
| 446 | /* Returns 1 if buffer uptodated, 0 on success, and -EIO on error. */ |
| 447 | static inline int bh_read(struct buffer_head *bh, blk_opf_t op_flags) |
| 448 | { |
| 449 | if (bh_uptodate_or_lock(bh)) |
| 450 | return 1; |
| 451 | return __bh_read(bh, op_flags, true); |
| 452 | } |
| 453 | |
| 454 | static inline void bh_read_batch(int nr, struct buffer_head *bhs[]) |
| 455 | { |
| 456 | __bh_read_batch(nr, bhs, 0, true); |
| 457 | } |
| 458 | |
| 459 | static inline void bh_readahead_batch(int nr, struct buffer_head *bhs[], |
| 460 | blk_opf_t op_flags) |
| 461 | { |
| 462 | __bh_read_batch(nr, bhs, op_flags, false); |
| 463 | } |
| 464 | |
| 465 | /** |
| 466 | * __bread() - Read a block. |
| 467 | * @bdev: The block device to read from. |
| 468 | * @block: Block number in units of block size. |
| 469 | * @size: The block size of this device in bytes. |
| 470 | * |
| 471 | * Read a specified block, and return the buffer head that refers |
| 472 | * to it. The memory is allocated from the movable area so that it can |
| 473 | * be migrated. The returned buffer head has its refcount increased. |
| 474 | * The caller should call brelse() when it has finished with the buffer. |
| 475 | * |
| 476 | * Context: May sleep waiting for I/O. |
| 477 | * Return: NULL if the block was unreadable. |
| 478 | */ |
| 479 | static inline struct buffer_head *__bread(struct block_device *bdev, |
| 480 | sector_t block, unsigned size) |
| 481 | { |
| 482 | return __bread_gfp(bdev, block, size, __GFP_MOVABLE); |
| 483 | } |
| 484 | |
| 485 | /** |
| 486 | * get_nth_bh - Get a reference on the n'th buffer after this one. |
| 487 | * @bh: The buffer to start counting from. |
| 488 | * @count: How many buffers to skip. |
| 489 | * |
| 490 | * This is primarily useful for finding the nth buffer in a folio; in |
| 491 | * that case you pass the head buffer and the byte offset in the folio |
| 492 | * divided by the block size. It can be used for other purposes, but |
| 493 | * it will wrap at the end of the folio rather than returning NULL or |
| 494 | * proceeding to the next folio for you. |
| 495 | * |
| 496 | * Return: The requested buffer with an elevated refcount. |
| 497 | */ |
| 498 | static inline __must_check |
| 499 | struct buffer_head *get_nth_bh(struct buffer_head *bh, unsigned int count) |
| 500 | { |
| 501 | while (count--) |
| 502 | bh = bh->b_this_page; |
| 503 | get_bh(bh); |
| 504 | return bh; |
| 505 | } |
| 506 | |
| 507 | bool block_dirty_folio(struct address_space *mapping, struct folio *folio); |
| 508 | |
| 509 | #ifdef CONFIG_BUFFER_HEAD |
| 510 | |
| 511 | void buffer_init(void); |
| 512 | bool try_to_free_buffers(struct folio *folio); |
| 513 | int inode_has_buffers(struct inode *inode); |
| 514 | void invalidate_inode_buffers(struct inode *inode); |
| 515 | int remove_inode_buffers(struct inode *inode); |
| 516 | int sync_mapping_buffers(struct address_space *mapping); |
| 517 | void invalidate_bh_lrus(void); |
| 518 | void invalidate_bh_lrus_cpu(void); |
| 519 | bool has_bh_in_lru(int cpu, void *dummy); |
| 520 | extern int buffer_heads_over_limit; |
| 521 | |
| 522 | #else /* CONFIG_BUFFER_HEAD */ |
| 523 | |
| 524 | static inline void buffer_init(void) {} |
| 525 | static inline bool try_to_free_buffers(struct folio *folio) { return true; } |
| 526 | static inline int inode_has_buffers(struct inode *inode) { return 0; } |
| 527 | static inline void invalidate_inode_buffers(struct inode *inode) {} |
| 528 | static inline int remove_inode_buffers(struct inode *inode) { return 1; } |
| 529 | static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } |
| 530 | static inline void invalidate_bh_lrus(void) {} |
| 531 | static inline void invalidate_bh_lrus_cpu(void) {} |
| 532 | static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; } |
| 533 | #define buffer_heads_over_limit 0 |
| 534 | |
| 535 | #endif /* CONFIG_BUFFER_HEAD */ |
| 536 | #endif /* _LINUX_BUFFER_HEAD_H */ |