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 struct page *b_page; /* the page this bh is mapped to */ 65 66 sector_t b_blocknr; /* start block number */ 67 size_t b_size; /* size of mapping */ 68 char *b_data; /* pointer to data within the page */ 69 70 struct block_device *b_bdev; 71 bh_end_io_t *b_end_io; /* I/O completion */ 72 void *b_private; /* reserved for b_end_io */ 73 struct list_head b_assoc_buffers; /* associated with another mapping */ 74 struct address_space *b_assoc_map; /* mapping this buffer is 75 associated with */ 76 atomic_t b_count; /* users using this buffer_head */ 77 spinlock_t b_uptodate_lock; /* Used by the first bh in a page, to 78 * serialise IO completion of other 79 * buffers in the page */ 80 }; 81 82 /* 83 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() 84 * and buffer_foo() functions. 85 * To avoid reset buffer flags that are already set, because that causes 86 * a costly cache line transition, check the flag first. 87 */ 88 #define BUFFER_FNS(bit, name) \ 89 static __always_inline void set_buffer_##name(struct buffer_head *bh) \ 90 { \ 91 if (!test_bit(BH_##bit, &(bh)->b_state)) \ 92 set_bit(BH_##bit, &(bh)->b_state); \ 93 } \ 94 static __always_inline void clear_buffer_##name(struct buffer_head *bh) \ 95 { \ 96 clear_bit(BH_##bit, &(bh)->b_state); \ 97 } \ 98 static __always_inline int buffer_##name(const struct buffer_head *bh) \ 99 { \ 100 return test_bit(BH_##bit, &(bh)->b_state); \ 101 } 102 103 /* 104 * test_set_buffer_foo() and test_clear_buffer_foo() 105 */ 106 #define TAS_BUFFER_FNS(bit, name) \ 107 static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \ 108 { \ 109 return test_and_set_bit(BH_##bit, &(bh)->b_state); \ 110 } \ 111 static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \ 112 { \ 113 return test_and_clear_bit(BH_##bit, &(bh)->b_state); \ 114 } \ 115 116 /* 117 * Emit the buffer bitops functions. Note that there are also functions 118 * of the form "mark_buffer_foo()". These are higher-level functions which 119 * do something in addition to setting a b_state bit. 120 */ 121 BUFFER_FNS(Uptodate, uptodate) 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 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) 140 141 /* If we *know* page->private refers to buffer_heads */ 142 #define page_buffers(page) \ 143 ({ \ 144 BUG_ON(!PagePrivate(page)); \ 145 ((struct buffer_head *)page_private(page)); \ 146 }) 147 #define page_has_buffers(page) PagePrivate(page) 148 #define folio_buffers(folio) folio_get_private(folio) 149 150 void buffer_check_dirty_writeback(struct folio *folio, 151 bool *dirty, bool *writeback); 152 153 /* 154 * Declarations 155 */ 156 157 void mark_buffer_dirty(struct buffer_head *bh); 158 void mark_buffer_write_io_error(struct buffer_head *bh); 159 void touch_buffer(struct buffer_head *bh); 160 void set_bh_page(struct buffer_head *bh, 161 struct page *page, unsigned long offset); 162 bool try_to_free_buffers(struct folio *); 163 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 164 bool retry); 165 void create_empty_buffers(struct page *, unsigned long, 166 unsigned long b_state); 167 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 168 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 169 void end_buffer_async_write(struct buffer_head *bh, int uptodate); 170 171 /* Things to do with buffers at mapping->private_list */ 172 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 173 int inode_has_buffers(struct inode *); 174 void invalidate_inode_buffers(struct inode *); 175 int remove_inode_buffers(struct inode *inode); 176 int sync_mapping_buffers(struct address_space *mapping); 177 void clean_bdev_aliases(struct block_device *bdev, sector_t block, 178 sector_t len); 179 static inline void clean_bdev_bh_alias(struct buffer_head *bh) 180 { 181 clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1); 182 } 183 184 void mark_buffer_async_write(struct buffer_head *bh); 185 void __wait_on_buffer(struct buffer_head *); 186 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 187 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, 188 unsigned size); 189 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block, 190 unsigned size, gfp_t gfp); 191 void __brelse(struct buffer_head *); 192 void __bforget(struct buffer_head *); 193 void __breadahead(struct block_device *, sector_t block, unsigned int size); 194 void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size, 195 gfp_t gfp); 196 struct buffer_head *__bread_gfp(struct block_device *, 197 sector_t block, unsigned size, gfp_t gfp); 198 void invalidate_bh_lrus(void); 199 void invalidate_bh_lrus_cpu(void); 200 bool has_bh_in_lru(int cpu, void *dummy); 201 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 202 void free_buffer_head(struct buffer_head * bh); 203 void unlock_buffer(struct buffer_head *bh); 204 void __lock_buffer(struct buffer_head *bh); 205 void ll_rw_block(blk_opf_t, int, struct buffer_head * bh[]); 206 int sync_dirty_buffer(struct buffer_head *bh); 207 int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags); 208 void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags); 209 int submit_bh(blk_opf_t, struct buffer_head *); 210 void write_boundary_block(struct block_device *bdev, 211 sector_t bblock, unsigned blocksize); 212 int bh_uptodate_or_lock(struct buffer_head *bh); 213 int bh_submit_read(struct buffer_head *bh); 214 215 extern int buffer_heads_over_limit; 216 217 /* 218 * Generic address_space_operations implementations for buffer_head-backed 219 * address_spaces. 220 */ 221 void block_invalidate_folio(struct folio *folio, size_t offset, size_t length); 222 int block_write_full_page(struct page *page, get_block_t *get_block, 223 struct writeback_control *wbc); 224 int __block_write_full_page(struct inode *inode, struct page *page, 225 get_block_t *get_block, struct writeback_control *wbc, 226 bh_end_io_t *handler); 227 int block_read_full_folio(struct folio *, get_block_t *); 228 bool block_is_partially_uptodate(struct folio *, size_t from, size_t count); 229 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, 230 struct page **pagep, get_block_t *get_block); 231 int __block_write_begin(struct page *page, loff_t pos, unsigned len, 232 get_block_t *get_block); 233 int block_write_end(struct file *, struct address_space *, 234 loff_t, unsigned, unsigned, 235 struct page *, void *); 236 int generic_write_end(struct file *, struct address_space *, 237 loff_t, unsigned, unsigned, 238 struct page *, void *); 239 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to); 240 void clean_page_buffers(struct page *page); 241 int cont_write_begin(struct file *, struct address_space *, loff_t, 242 unsigned, struct page **, void **, 243 get_block_t *, loff_t *); 244 int generic_cont_expand_simple(struct inode *inode, loff_t size); 245 int block_commit_write(struct page *page, unsigned from, unsigned to); 246 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 247 get_block_t get_block); 248 /* Convert errno to return value from ->page_mkwrite() call */ 249 static inline vm_fault_t block_page_mkwrite_return(int err) 250 { 251 if (err == 0) 252 return VM_FAULT_LOCKED; 253 if (err == -EFAULT || err == -EAGAIN) 254 return VM_FAULT_NOPAGE; 255 if (err == -ENOMEM) 256 return VM_FAULT_OOM; 257 /* -ENOSPC, -EDQUOT, -EIO ... */ 258 return VM_FAULT_SIGBUS; 259 } 260 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 261 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 262 263 #ifdef CONFIG_MIGRATION 264 extern int buffer_migrate_folio(struct address_space *, 265 struct folio *dst, struct folio *src, enum migrate_mode); 266 extern int buffer_migrate_folio_norefs(struct address_space *, 267 struct folio *dst, struct folio *src, enum migrate_mode); 268 #else 269 #define buffer_migrate_folio NULL 270 #define buffer_migrate_folio_norefs NULL 271 #endif 272 273 void buffer_init(void); 274 275 /* 276 * inline definitions 277 */ 278 279 static inline void get_bh(struct buffer_head *bh) 280 { 281 atomic_inc(&bh->b_count); 282 } 283 284 static inline void put_bh(struct buffer_head *bh) 285 { 286 smp_mb__before_atomic(); 287 atomic_dec(&bh->b_count); 288 } 289 290 static inline void brelse(struct buffer_head *bh) 291 { 292 if (bh) 293 __brelse(bh); 294 } 295 296 static inline void bforget(struct buffer_head *bh) 297 { 298 if (bh) 299 __bforget(bh); 300 } 301 302 static inline struct buffer_head * 303 sb_bread(struct super_block *sb, sector_t block) 304 { 305 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 306 } 307 308 static inline struct buffer_head * 309 sb_bread_unmovable(struct super_block *sb, sector_t block) 310 { 311 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0); 312 } 313 314 static inline void 315 sb_breadahead(struct super_block *sb, sector_t block) 316 { 317 __breadahead(sb->s_bdev, block, sb->s_blocksize); 318 } 319 320 static inline void 321 sb_breadahead_unmovable(struct super_block *sb, sector_t block) 322 { 323 __breadahead_gfp(sb->s_bdev, block, sb->s_blocksize, 0); 324 } 325 326 static inline struct buffer_head * 327 sb_getblk(struct super_block *sb, sector_t block) 328 { 329 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 330 } 331 332 333 static inline struct buffer_head * 334 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp) 335 { 336 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp); 337 } 338 339 static inline struct buffer_head * 340 sb_find_get_block(struct super_block *sb, sector_t block) 341 { 342 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 343 } 344 345 static inline void 346 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 347 { 348 set_buffer_mapped(bh); 349 bh->b_bdev = sb->s_bdev; 350 bh->b_blocknr = block; 351 bh->b_size = sb->s_blocksize; 352 } 353 354 static inline void wait_on_buffer(struct buffer_head *bh) 355 { 356 might_sleep(); 357 if (buffer_locked(bh)) 358 __wait_on_buffer(bh); 359 } 360 361 static inline int trylock_buffer(struct buffer_head *bh) 362 { 363 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); 364 } 365 366 static inline void lock_buffer(struct buffer_head *bh) 367 { 368 might_sleep(); 369 if (!trylock_buffer(bh)) 370 __lock_buffer(bh); 371 } 372 373 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev, 374 sector_t block, 375 unsigned size) 376 { 377 return __getblk_gfp(bdev, block, size, 0); 378 } 379 380 static inline struct buffer_head *__getblk(struct block_device *bdev, 381 sector_t block, 382 unsigned size) 383 { 384 return __getblk_gfp(bdev, block, size, __GFP_MOVABLE); 385 } 386 387 /** 388 * __bread() - reads a specified block and returns the bh 389 * @bdev: the block_device to read from 390 * @block: number of block 391 * @size: size (in bytes) to read 392 * 393 * Reads a specified block, and returns buffer head that contains it. 394 * The page cache is allocated from movable area so that it can be migrated. 395 * It returns NULL if the block was unreadable. 396 */ 397 static inline struct buffer_head * 398 __bread(struct block_device *bdev, sector_t block, unsigned size) 399 { 400 return __bread_gfp(bdev, block, size, __GFP_MOVABLE); 401 } 402 403 bool block_dirty_folio(struct address_space *mapping, struct folio *folio); 404 405 #else /* CONFIG_BLOCK */ 406 407 static inline void buffer_init(void) {} 408 static inline bool try_to_free_buffers(struct folio *folio) { return true; } 409 static inline int inode_has_buffers(struct inode *inode) { return 0; } 410 static inline void invalidate_inode_buffers(struct inode *inode) {} 411 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 412 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 413 static inline void invalidate_bh_lrus_cpu(void) {} 414 static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; } 415 #define buffer_heads_over_limit 0 416 417 #endif /* CONFIG_BLOCK */ 418 #endif /* _LINUX_BUFFER_HEAD_H */ 419