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 BUFFER_FNS(Dirty, dirty) 125 TAS_BUFFER_FNS(Dirty, dirty) 126 BUFFER_FNS(Lock, locked) 127 BUFFER_FNS(Req, req) 128 TAS_BUFFER_FNS(Req, req) 129 BUFFER_FNS(Mapped, mapped) 130 BUFFER_FNS(New, new) 131 BUFFER_FNS(Async_Read, async_read) 132 BUFFER_FNS(Async_Write, async_write) 133 BUFFER_FNS(Delay, delay) 134 BUFFER_FNS(Boundary, boundary) 135 BUFFER_FNS(Write_EIO, write_io_error) 136 BUFFER_FNS(Unwritten, unwritten) 137 BUFFER_FNS(Meta, meta) 138 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 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 smp_mb__before_atomic(); 159 set_bit(BH_Uptodate, &bh->b_state); 160 } 161 162 static __always_inline void clear_buffer_uptodate(struct buffer_head *bh) 163 { 164 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 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 void folio_set_bh(struct buffer_head *bh, struct folio *folio, 200 unsigned long offset); 201 bool try_to_free_buffers(struct folio *); 202 struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size, 203 bool retry); 204 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 205 bool retry); 206 void create_empty_buffers(struct page *, unsigned long, 207 unsigned long b_state); 208 void folio_create_empty_buffers(struct folio *folio, unsigned long blocksize, 209 unsigned long b_state); 210 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 211 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 212 void end_buffer_async_write(struct buffer_head *bh, int uptodate); 213 214 /* Things to do with buffers at mapping->private_list */ 215 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 216 int inode_has_buffers(struct inode *); 217 void invalidate_inode_buffers(struct inode *); 218 int remove_inode_buffers(struct inode *inode); 219 int sync_mapping_buffers(struct address_space *mapping); 220 int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end, 221 bool datasync); 222 int generic_buffers_fsync(struct file *file, loff_t start, loff_t end, 223 bool datasync); 224 void clean_bdev_aliases(struct block_device *bdev, sector_t block, 225 sector_t len); 226 static inline void clean_bdev_bh_alias(struct buffer_head *bh) 227 { 228 clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1); 229 } 230 231 void mark_buffer_async_write(struct buffer_head *bh); 232 void __wait_on_buffer(struct buffer_head *); 233 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 234 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, 235 unsigned size); 236 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block, 237 unsigned size, gfp_t gfp); 238 void __brelse(struct buffer_head *); 239 void __bforget(struct buffer_head *); 240 void __breadahead(struct block_device *, sector_t block, unsigned int size); 241 struct buffer_head *__bread_gfp(struct block_device *, 242 sector_t block, unsigned size, gfp_t gfp); 243 void invalidate_bh_lrus(void); 244 void invalidate_bh_lrus_cpu(void); 245 bool has_bh_in_lru(int cpu, void *dummy); 246 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 247 void free_buffer_head(struct buffer_head * bh); 248 void unlock_buffer(struct buffer_head *bh); 249 void __lock_buffer(struct buffer_head *bh); 250 int sync_dirty_buffer(struct buffer_head *bh); 251 int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags); 252 void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags); 253 void submit_bh(blk_opf_t, struct buffer_head *); 254 void write_boundary_block(struct block_device *bdev, 255 sector_t bblock, unsigned blocksize); 256 int bh_uptodate_or_lock(struct buffer_head *bh); 257 int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait); 258 void __bh_read_batch(int nr, struct buffer_head *bhs[], 259 blk_opf_t op_flags, bool force_lock); 260 261 extern int buffer_heads_over_limit; 262 263 /* 264 * Generic address_space_operations implementations for buffer_head-backed 265 * address_spaces. 266 */ 267 void block_invalidate_folio(struct folio *folio, size_t offset, size_t length); 268 int block_write_full_page(struct page *page, get_block_t *get_block, 269 struct writeback_control *wbc); 270 int __block_write_full_folio(struct inode *inode, struct folio *folio, 271 get_block_t *get_block, struct writeback_control *wbc, 272 bh_end_io_t *handler); 273 int block_read_full_folio(struct folio *, get_block_t *); 274 bool block_is_partially_uptodate(struct folio *, size_t from, size_t count); 275 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, 276 struct page **pagep, get_block_t *get_block); 277 int __block_write_begin(struct page *page, loff_t pos, unsigned len, 278 get_block_t *get_block); 279 int block_write_end(struct file *, struct address_space *, 280 loff_t, unsigned, unsigned, 281 struct page *, void *); 282 int generic_write_end(struct file *, struct address_space *, 283 loff_t, unsigned, unsigned, 284 struct page *, void *); 285 void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to); 286 void clean_page_buffers(struct page *page); 287 int cont_write_begin(struct file *, struct address_space *, loff_t, 288 unsigned, struct page **, void **, 289 get_block_t *, loff_t *); 290 int generic_cont_expand_simple(struct inode *inode, loff_t size); 291 int block_commit_write(struct page *page, unsigned from, unsigned to); 292 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 293 get_block_t get_block); 294 /* Convert errno to return value from ->page_mkwrite() call */ 295 static inline vm_fault_t block_page_mkwrite_return(int err) 296 { 297 if (err == 0) 298 return VM_FAULT_LOCKED; 299 if (err == -EFAULT || err == -EAGAIN) 300 return VM_FAULT_NOPAGE; 301 if (err == -ENOMEM) 302 return VM_FAULT_OOM; 303 /* -ENOSPC, -EDQUOT, -EIO ... */ 304 return VM_FAULT_SIGBUS; 305 } 306 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 307 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 308 309 #ifdef CONFIG_MIGRATION 310 extern int buffer_migrate_folio(struct address_space *, 311 struct folio *dst, struct folio *src, enum migrate_mode); 312 extern int buffer_migrate_folio_norefs(struct address_space *, 313 struct folio *dst, struct folio *src, enum migrate_mode); 314 #else 315 #define buffer_migrate_folio NULL 316 #define buffer_migrate_folio_norefs NULL 317 #endif 318 319 void buffer_init(void); 320 321 /* 322 * inline definitions 323 */ 324 325 static inline void get_bh(struct buffer_head *bh) 326 { 327 atomic_inc(&bh->b_count); 328 } 329 330 static inline void put_bh(struct buffer_head *bh) 331 { 332 smp_mb__before_atomic(); 333 atomic_dec(&bh->b_count); 334 } 335 336 static inline void brelse(struct buffer_head *bh) 337 { 338 if (bh) 339 __brelse(bh); 340 } 341 342 static inline void bforget(struct buffer_head *bh) 343 { 344 if (bh) 345 __bforget(bh); 346 } 347 348 static inline struct buffer_head * 349 sb_bread(struct super_block *sb, sector_t block) 350 { 351 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 352 } 353 354 static inline struct buffer_head * 355 sb_bread_unmovable(struct super_block *sb, sector_t block) 356 { 357 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0); 358 } 359 360 static inline void 361 sb_breadahead(struct super_block *sb, sector_t block) 362 { 363 __breadahead(sb->s_bdev, block, sb->s_blocksize); 364 } 365 366 static inline struct buffer_head * 367 sb_getblk(struct super_block *sb, sector_t block) 368 { 369 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 370 } 371 372 373 static inline struct buffer_head * 374 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp) 375 { 376 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp); 377 } 378 379 static inline struct buffer_head * 380 sb_find_get_block(struct super_block *sb, sector_t block) 381 { 382 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 383 } 384 385 static inline void 386 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 387 { 388 set_buffer_mapped(bh); 389 bh->b_bdev = sb->s_bdev; 390 bh->b_blocknr = block; 391 bh->b_size = sb->s_blocksize; 392 } 393 394 static inline void wait_on_buffer(struct buffer_head *bh) 395 { 396 might_sleep(); 397 if (buffer_locked(bh)) 398 __wait_on_buffer(bh); 399 } 400 401 static inline int trylock_buffer(struct buffer_head *bh) 402 { 403 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); 404 } 405 406 static inline void lock_buffer(struct buffer_head *bh) 407 { 408 might_sleep(); 409 if (!trylock_buffer(bh)) 410 __lock_buffer(bh); 411 } 412 413 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev, 414 sector_t block, 415 unsigned size) 416 { 417 return __getblk_gfp(bdev, block, size, 0); 418 } 419 420 static inline struct buffer_head *__getblk(struct block_device *bdev, 421 sector_t block, 422 unsigned size) 423 { 424 return __getblk_gfp(bdev, block, size, __GFP_MOVABLE); 425 } 426 427 static inline void bh_readahead(struct buffer_head *bh, blk_opf_t op_flags) 428 { 429 if (!buffer_uptodate(bh) && trylock_buffer(bh)) { 430 if (!buffer_uptodate(bh)) 431 __bh_read(bh, op_flags, false); 432 else 433 unlock_buffer(bh); 434 } 435 } 436 437 static inline void bh_read_nowait(struct buffer_head *bh, blk_opf_t op_flags) 438 { 439 if (!bh_uptodate_or_lock(bh)) 440 __bh_read(bh, op_flags, false); 441 } 442 443 /* Returns 1 if buffer uptodated, 0 on success, and -EIO on error. */ 444 static inline int bh_read(struct buffer_head *bh, blk_opf_t op_flags) 445 { 446 if (bh_uptodate_or_lock(bh)) 447 return 1; 448 return __bh_read(bh, op_flags, true); 449 } 450 451 static inline void bh_read_batch(int nr, struct buffer_head *bhs[]) 452 { 453 __bh_read_batch(nr, bhs, 0, true); 454 } 455 456 static inline void bh_readahead_batch(int nr, struct buffer_head *bhs[], 457 blk_opf_t op_flags) 458 { 459 __bh_read_batch(nr, bhs, op_flags, false); 460 } 461 462 /** 463 * __bread() - reads a specified block and returns the bh 464 * @bdev: the block_device to read from 465 * @block: number of block 466 * @size: size (in bytes) to read 467 * 468 * Reads a specified block, and returns buffer head that contains it. 469 * The page cache is allocated from movable area so that it can be migrated. 470 * It returns NULL if the block was unreadable. 471 */ 472 static inline struct buffer_head * 473 __bread(struct block_device *bdev, sector_t block, unsigned size) 474 { 475 return __bread_gfp(bdev, block, size, __GFP_MOVABLE); 476 } 477 478 bool block_dirty_folio(struct address_space *mapping, struct folio *folio); 479 480 #else /* CONFIG_BLOCK */ 481 482 static inline void buffer_init(void) {} 483 static inline bool try_to_free_buffers(struct folio *folio) { return true; } 484 static inline int inode_has_buffers(struct inode *inode) { return 0; } 485 static inline void invalidate_inode_buffers(struct inode *inode) {} 486 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 487 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 488 static inline void invalidate_bh_lrus_cpu(void) {} 489 static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; } 490 #define buffer_heads_over_limit 0 491 492 #endif /* CONFIG_BLOCK */ 493 #endif /* _LINUX_BUFFER_HEAD_H */ 494