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 page (via a page_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 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) 175 176 /* If we *know* page->private refers to buffer_heads */ 177 #define page_buffers(page) \ 178 ({ \ 179 BUG_ON(!PagePrivate(page)); \ 180 ((struct buffer_head *)page_private(page)); \ 181 }) 182 #define page_has_buffers(page) PagePrivate(page) 183 #define folio_buffers(folio) folio_get_private(folio) 184 185 void buffer_check_dirty_writeback(struct folio *folio, 186 bool *dirty, bool *writeback); 187 188 /* 189 * Declarations 190 */ 191 192 void mark_buffer_dirty(struct buffer_head *bh); 193 void mark_buffer_write_io_error(struct buffer_head *bh); 194 void touch_buffer(struct buffer_head *bh); 195 void folio_set_bh(struct buffer_head *bh, struct folio *folio, 196 unsigned long offset); 197 struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size, 198 bool retry); 199 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 200 bool retry); 201 void create_empty_buffers(struct page *, unsigned long, 202 unsigned long b_state); 203 void folio_create_empty_buffers(struct folio *folio, unsigned long blocksize, 204 unsigned long b_state); 205 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 206 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 207 void end_buffer_async_write(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 *__getblk_gfp(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_page(struct page *page, get_block_t *get_block, 255 struct writeback_control *wbc); 256 int __block_write_full_folio(struct inode *inode, struct folio *folio, 257 get_block_t *get_block, struct writeback_control *wbc, 258 bh_end_io_t *handler); 259 int block_read_full_folio(struct folio *, get_block_t *); 260 bool block_is_partially_uptodate(struct folio *, size_t from, size_t count); 261 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, 262 struct page **pagep, get_block_t *get_block); 263 int __block_write_begin(struct page *page, loff_t pos, unsigned len, 264 get_block_t *get_block); 265 int block_write_end(struct file *, struct address_space *, 266 loff_t, unsigned, unsigned, 267 struct page *, void *); 268 int generic_write_end(struct file *, struct address_space *, 269 loff_t, unsigned, unsigned, 270 struct page *, void *); 271 void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to); 272 void clean_page_buffers(struct page *page); 273 int cont_write_begin(struct file *, struct address_space *, loff_t, 274 unsigned, struct page **, void **, 275 get_block_t *, loff_t *); 276 int generic_cont_expand_simple(struct inode *inode, loff_t size); 277 void block_commit_write(struct page *page, unsigned int from, unsigned int to); 278 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 279 get_block_t get_block); 280 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 281 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 282 283 #ifdef CONFIG_MIGRATION 284 extern int buffer_migrate_folio(struct address_space *, 285 struct folio *dst, struct folio *src, enum migrate_mode); 286 extern int buffer_migrate_folio_norefs(struct address_space *, 287 struct folio *dst, struct folio *src, enum migrate_mode); 288 #else 289 #define buffer_migrate_folio NULL 290 #define buffer_migrate_folio_norefs NULL 291 #endif 292 293 /* 294 * inline definitions 295 */ 296 297 static inline void get_bh(struct buffer_head *bh) 298 { 299 atomic_inc(&bh->b_count); 300 } 301 302 static inline void put_bh(struct buffer_head *bh) 303 { 304 smp_mb__before_atomic(); 305 atomic_dec(&bh->b_count); 306 } 307 308 static inline void brelse(struct buffer_head *bh) 309 { 310 if (bh) 311 __brelse(bh); 312 } 313 314 static inline void bforget(struct buffer_head *bh) 315 { 316 if (bh) 317 __bforget(bh); 318 } 319 320 static inline struct buffer_head * 321 sb_bread(struct super_block *sb, sector_t block) 322 { 323 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 324 } 325 326 static inline struct buffer_head * 327 sb_bread_unmovable(struct super_block *sb, sector_t block) 328 { 329 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0); 330 } 331 332 static inline void 333 sb_breadahead(struct super_block *sb, sector_t block) 334 { 335 __breadahead(sb->s_bdev, block, sb->s_blocksize); 336 } 337 338 static inline struct buffer_head * 339 sb_getblk(struct super_block *sb, sector_t block) 340 { 341 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 342 } 343 344 345 static inline struct buffer_head * 346 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp) 347 { 348 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp); 349 } 350 351 static inline struct buffer_head * 352 sb_find_get_block(struct super_block *sb, sector_t block) 353 { 354 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 355 } 356 357 static inline void 358 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 359 { 360 set_buffer_mapped(bh); 361 bh->b_bdev = sb->s_bdev; 362 bh->b_blocknr = block; 363 bh->b_size = sb->s_blocksize; 364 } 365 366 static inline void wait_on_buffer(struct buffer_head *bh) 367 { 368 might_sleep(); 369 if (buffer_locked(bh)) 370 __wait_on_buffer(bh); 371 } 372 373 static inline int trylock_buffer(struct buffer_head *bh) 374 { 375 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); 376 } 377 378 static inline void lock_buffer(struct buffer_head *bh) 379 { 380 might_sleep(); 381 if (!trylock_buffer(bh)) 382 __lock_buffer(bh); 383 } 384 385 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev, 386 sector_t block, 387 unsigned size) 388 { 389 return __getblk_gfp(bdev, block, size, 0); 390 } 391 392 static inline struct buffer_head *__getblk(struct block_device *bdev, 393 sector_t block, 394 unsigned size) 395 { 396 return __getblk_gfp(bdev, block, size, __GFP_MOVABLE); 397 } 398 399 static inline void bh_readahead(struct buffer_head *bh, blk_opf_t op_flags) 400 { 401 if (!buffer_uptodate(bh) && trylock_buffer(bh)) { 402 if (!buffer_uptodate(bh)) 403 __bh_read(bh, op_flags, false); 404 else 405 unlock_buffer(bh); 406 } 407 } 408 409 static inline void bh_read_nowait(struct buffer_head *bh, blk_opf_t op_flags) 410 { 411 if (!bh_uptodate_or_lock(bh)) 412 __bh_read(bh, op_flags, false); 413 } 414 415 /* Returns 1 if buffer uptodated, 0 on success, and -EIO on error. */ 416 static inline int bh_read(struct buffer_head *bh, blk_opf_t op_flags) 417 { 418 if (bh_uptodate_or_lock(bh)) 419 return 1; 420 return __bh_read(bh, op_flags, true); 421 } 422 423 static inline void bh_read_batch(int nr, struct buffer_head *bhs[]) 424 { 425 __bh_read_batch(nr, bhs, 0, true); 426 } 427 428 static inline void bh_readahead_batch(int nr, struct buffer_head *bhs[], 429 blk_opf_t op_flags) 430 { 431 __bh_read_batch(nr, bhs, op_flags, false); 432 } 433 434 /** 435 * __bread() - reads a specified block and returns the bh 436 * @bdev: the block_device to read from 437 * @block: number of block 438 * @size: size (in bytes) to read 439 * 440 * Reads a specified block, and returns buffer head that contains it. 441 * The page cache is allocated from movable area so that it can be migrated. 442 * It returns NULL if the block was unreadable. 443 */ 444 static inline struct buffer_head * 445 __bread(struct block_device *bdev, sector_t block, unsigned size) 446 { 447 return __bread_gfp(bdev, block, size, __GFP_MOVABLE); 448 } 449 450 bool block_dirty_folio(struct address_space *mapping, struct folio *folio); 451 452 #ifdef CONFIG_BUFFER_HEAD 453 454 void buffer_init(void); 455 bool try_to_free_buffers(struct folio *folio); 456 int inode_has_buffers(struct inode *inode); 457 void invalidate_inode_buffers(struct inode *inode); 458 int remove_inode_buffers(struct inode *inode); 459 int sync_mapping_buffers(struct address_space *mapping); 460 void invalidate_bh_lrus(void); 461 void invalidate_bh_lrus_cpu(void); 462 bool has_bh_in_lru(int cpu, void *dummy); 463 extern int buffer_heads_over_limit; 464 465 #else /* CONFIG_BUFFER_HEAD */ 466 467 static inline void buffer_init(void) {} 468 static inline bool try_to_free_buffers(struct folio *folio) { return true; } 469 static inline int inode_has_buffers(struct inode *inode) { return 0; } 470 static inline void invalidate_inode_buffers(struct inode *inode) {} 471 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 472 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 473 static inline void invalidate_bh_lrus(void) {} 474 static inline void invalidate_bh_lrus_cpu(void) {} 475 static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; } 476 #define buffer_heads_over_limit 0 477 478 #endif /* CONFIG_BUFFER_HEAD */ 479 #endif /* _LINUX_BUFFER_HEAD_H */ 480