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/fs.h> 13 #include <linux/linkage.h> 14 #include <linux/pagemap.h> 15 #include <linux/wait.h> 16 #include <linux/atomic.h> 17 18 #ifdef CONFIG_BLOCK 19 20 enum bh_state_bits { 21 BH_Uptodate, /* Contains valid data */ 22 BH_Dirty, /* Is dirty */ 23 BH_Lock, /* Is locked */ 24 BH_Req, /* Has been submitted for I/O */ 25 26 BH_Mapped, /* Has a disk mapping */ 27 BH_New, /* Disk mapping was newly created by get_block */ 28 BH_Async_Read, /* Is under end_buffer_async_read I/O */ 29 BH_Async_Write, /* Is under end_buffer_async_write I/O */ 30 BH_Delay, /* Buffer is not yet allocated on disk */ 31 BH_Boundary, /* Block is followed by a discontiguity */ 32 BH_Write_EIO, /* I/O error on write */ 33 BH_Unwritten, /* Buffer is allocated on disk but not written */ 34 BH_Quiet, /* Buffer Error Prinks to be quiet */ 35 BH_Meta, /* Buffer contains metadata */ 36 BH_Prio, /* Buffer should be submitted with REQ_PRIO */ 37 BH_Defer_Completion, /* Defer AIO completion to workqueue */ 38 39 BH_PrivateStart,/* not a state bit, but the first bit available 40 * for private allocation by other entities 41 */ 42 }; 43 44 #define MAX_BUF_PER_PAGE (PAGE_SIZE / 512) 45 46 struct page; 47 struct buffer_head; 48 struct address_space; 49 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate); 50 51 /* 52 * Historically, a buffer_head was used to map a single block 53 * within a page, and of course as the unit of I/O through the 54 * filesystem and block layers. Nowadays the basic I/O unit 55 * is the bio, and buffer_heads are used for extracting block 56 * mappings (via a get_block_t call), for tracking state within 57 * a page (via a page_mapping) and for wrapping bio submission 58 * for backward compatibility reasons (e.g. submit_bh). 59 */ 60 struct buffer_head { 61 unsigned long b_state; /* buffer state bitmap (see above) */ 62 struct buffer_head *b_this_page;/* circular list of page's buffers */ 63 struct page *b_page; /* the page this bh is mapped to */ 64 65 sector_t b_blocknr; /* start block number */ 66 size_t b_size; /* size of mapping */ 67 char *b_data; /* pointer to data within the page */ 68 69 struct block_device *b_bdev; 70 bh_end_io_t *b_end_io; /* I/O completion */ 71 void *b_private; /* reserved for b_end_io */ 72 struct list_head b_assoc_buffers; /* associated with another mapping */ 73 struct address_space *b_assoc_map; /* mapping this buffer is 74 associated with */ 75 atomic_t b_count; /* users using this buffer_head */ 76 spinlock_t b_uptodate_lock; /* Used by the first bh in a page, to 77 * serialise IO completion of other 78 * buffers in the page */ 79 }; 80 81 /* 82 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() 83 * and buffer_foo() functions. 84 * To avoid reset buffer flags that are already set, because that causes 85 * a costly cache line transition, check the flag first. 86 */ 87 #define BUFFER_FNS(bit, name) \ 88 static __always_inline void set_buffer_##name(struct buffer_head *bh) \ 89 { \ 90 if (!test_bit(BH_##bit, &(bh)->b_state)) \ 91 set_bit(BH_##bit, &(bh)->b_state); \ 92 } \ 93 static __always_inline void clear_buffer_##name(struct buffer_head *bh) \ 94 { \ 95 clear_bit(BH_##bit, &(bh)->b_state); \ 96 } \ 97 static __always_inline int buffer_##name(const struct buffer_head *bh) \ 98 { \ 99 return test_bit(BH_##bit, &(bh)->b_state); \ 100 } 101 102 /* 103 * test_set_buffer_foo() and test_clear_buffer_foo() 104 */ 105 #define TAS_BUFFER_FNS(bit, name) \ 106 static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \ 107 { \ 108 return test_and_set_bit(BH_##bit, &(bh)->b_state); \ 109 } \ 110 static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \ 111 { \ 112 return test_and_clear_bit(BH_##bit, &(bh)->b_state); \ 113 } \ 114 115 /* 116 * Emit the buffer bitops functions. Note that there are also functions 117 * of the form "mark_buffer_foo()". These are higher-level functions which 118 * do something in addition to setting a b_state bit. 119 */ 120 BUFFER_FNS(Uptodate, uptodate) 121 BUFFER_FNS(Dirty, dirty) 122 TAS_BUFFER_FNS(Dirty, dirty) 123 BUFFER_FNS(Lock, locked) 124 BUFFER_FNS(Req, req) 125 TAS_BUFFER_FNS(Req, req) 126 BUFFER_FNS(Mapped, mapped) 127 BUFFER_FNS(New, new) 128 BUFFER_FNS(Async_Read, async_read) 129 BUFFER_FNS(Async_Write, async_write) 130 BUFFER_FNS(Delay, delay) 131 BUFFER_FNS(Boundary, boundary) 132 BUFFER_FNS(Write_EIO, write_io_error) 133 BUFFER_FNS(Unwritten, unwritten) 134 BUFFER_FNS(Meta, meta) 135 BUFFER_FNS(Prio, prio) 136 BUFFER_FNS(Defer_Completion, defer_completion) 137 138 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) 139 140 /* If we *know* page->private refers to buffer_heads */ 141 #define page_buffers(page) \ 142 ({ \ 143 BUG_ON(!PagePrivate(page)); \ 144 ((struct buffer_head *)page_private(page)); \ 145 }) 146 #define page_has_buffers(page) PagePrivate(page) 147 #define folio_buffers(folio) folio_get_private(folio) 148 149 void buffer_check_dirty_writeback(struct folio *folio, 150 bool *dirty, bool *writeback); 151 152 /* 153 * Declarations 154 */ 155 156 void mark_buffer_dirty(struct buffer_head *bh); 157 void mark_buffer_write_io_error(struct buffer_head *bh); 158 void touch_buffer(struct buffer_head *bh); 159 void set_bh_page(struct buffer_head *bh, 160 struct page *page, unsigned long offset); 161 bool try_to_free_buffers(struct folio *); 162 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 163 bool retry); 164 void create_empty_buffers(struct page *, unsigned long, 165 unsigned long b_state); 166 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 167 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 168 void end_buffer_async_write(struct buffer_head *bh, int uptodate); 169 170 /* Things to do with buffers at mapping->private_list */ 171 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 172 int inode_has_buffers(struct inode *); 173 void invalidate_inode_buffers(struct inode *); 174 int remove_inode_buffers(struct inode *inode); 175 int sync_mapping_buffers(struct address_space *mapping); 176 void clean_bdev_aliases(struct block_device *bdev, sector_t block, 177 sector_t len); 178 static inline void clean_bdev_bh_alias(struct buffer_head *bh) 179 { 180 clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1); 181 } 182 183 void mark_buffer_async_write(struct buffer_head *bh); 184 void __wait_on_buffer(struct buffer_head *); 185 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 186 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, 187 unsigned size); 188 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block, 189 unsigned size, gfp_t gfp); 190 void __brelse(struct buffer_head *); 191 void __bforget(struct buffer_head *); 192 void __breadahead(struct block_device *, sector_t block, unsigned int size); 193 void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size, 194 gfp_t gfp); 195 struct buffer_head *__bread_gfp(struct block_device *, 196 sector_t block, unsigned size, gfp_t gfp); 197 void invalidate_bh_lrus(void); 198 void invalidate_bh_lrus_cpu(void); 199 bool has_bh_in_lru(int cpu, void *dummy); 200 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 201 void free_buffer_head(struct buffer_head * bh); 202 void unlock_buffer(struct buffer_head *bh); 203 void __lock_buffer(struct buffer_head *bh); 204 void ll_rw_block(int, int, int, struct buffer_head * bh[]); 205 int sync_dirty_buffer(struct buffer_head *bh); 206 int __sync_dirty_buffer(struct buffer_head *bh, int op_flags); 207 void write_dirty_buffer(struct buffer_head *bh, int op_flags); 208 int submit_bh(int, int, struct buffer_head *); 209 void write_boundary_block(struct block_device *bdev, 210 sector_t bblock, unsigned blocksize); 211 int bh_uptodate_or_lock(struct buffer_head *bh); 212 int bh_submit_read(struct buffer_head *bh); 213 214 extern int buffer_heads_over_limit; 215 216 /* 217 * Generic address_space_operations implementations for buffer_head-backed 218 * address_spaces. 219 */ 220 void block_invalidate_folio(struct folio *folio, size_t offset, size_t length); 221 int block_write_full_page(struct page *page, get_block_t *get_block, 222 struct writeback_control *wbc); 223 int __block_write_full_page(struct inode *inode, struct page *page, 224 get_block_t *get_block, struct writeback_control *wbc, 225 bh_end_io_t *handler); 226 int block_read_full_folio(struct folio *, get_block_t *); 227 bool block_is_partially_uptodate(struct folio *, size_t from, size_t count); 228 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, 229 struct page **pagep, get_block_t *get_block); 230 int __block_write_begin(struct page *page, loff_t pos, unsigned len, 231 get_block_t *get_block); 232 int block_write_end(struct file *, struct address_space *, 233 loff_t, unsigned, unsigned, 234 struct page *, void *); 235 int generic_write_end(struct file *, struct address_space *, 236 loff_t, unsigned, unsigned, 237 struct page *, void *); 238 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to); 239 void clean_page_buffers(struct page *page); 240 int cont_write_begin(struct file *, struct address_space *, loff_t, 241 unsigned, struct page **, void **, 242 get_block_t *, loff_t *); 243 int generic_cont_expand_simple(struct inode *inode, loff_t size); 244 int block_commit_write(struct page *page, unsigned from, unsigned to); 245 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 246 get_block_t get_block); 247 /* Convert errno to return value from ->page_mkwrite() call */ 248 static inline vm_fault_t block_page_mkwrite_return(int err) 249 { 250 if (err == 0) 251 return VM_FAULT_LOCKED; 252 if (err == -EFAULT || err == -EAGAIN) 253 return VM_FAULT_NOPAGE; 254 if (err == -ENOMEM) 255 return VM_FAULT_OOM; 256 /* -ENOSPC, -EDQUOT, -EIO ... */ 257 return VM_FAULT_SIGBUS; 258 } 259 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 260 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 261 int nobh_write_begin(struct address_space *, loff_t, unsigned len, 262 struct page **, void **, get_block_t*); 263 int nobh_write_end(struct file *, struct address_space *, 264 loff_t, unsigned, unsigned, 265 struct page *, void *); 266 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *); 267 int nobh_writepage(struct page *page, get_block_t *get_block, 268 struct writeback_control *wbc); 269 270 void buffer_init(void); 271 272 /* 273 * inline definitions 274 */ 275 276 static inline void get_bh(struct buffer_head *bh) 277 { 278 atomic_inc(&bh->b_count); 279 } 280 281 static inline void put_bh(struct buffer_head *bh) 282 { 283 smp_mb__before_atomic(); 284 atomic_dec(&bh->b_count); 285 } 286 287 static inline void brelse(struct buffer_head *bh) 288 { 289 if (bh) 290 __brelse(bh); 291 } 292 293 static inline void bforget(struct buffer_head *bh) 294 { 295 if (bh) 296 __bforget(bh); 297 } 298 299 static inline struct buffer_head * 300 sb_bread(struct super_block *sb, sector_t block) 301 { 302 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 303 } 304 305 static inline struct buffer_head * 306 sb_bread_unmovable(struct super_block *sb, sector_t block) 307 { 308 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0); 309 } 310 311 static inline void 312 sb_breadahead(struct super_block *sb, sector_t block) 313 { 314 __breadahead(sb->s_bdev, block, sb->s_blocksize); 315 } 316 317 static inline void 318 sb_breadahead_unmovable(struct super_block *sb, sector_t block) 319 { 320 __breadahead_gfp(sb->s_bdev, block, sb->s_blocksize, 0); 321 } 322 323 static inline struct buffer_head * 324 sb_getblk(struct super_block *sb, sector_t block) 325 { 326 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 327 } 328 329 330 static inline struct buffer_head * 331 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp) 332 { 333 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp); 334 } 335 336 static inline struct buffer_head * 337 sb_find_get_block(struct super_block *sb, sector_t block) 338 { 339 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 340 } 341 342 static inline void 343 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 344 { 345 set_buffer_mapped(bh); 346 bh->b_bdev = sb->s_bdev; 347 bh->b_blocknr = block; 348 bh->b_size = sb->s_blocksize; 349 } 350 351 static inline void wait_on_buffer(struct buffer_head *bh) 352 { 353 might_sleep(); 354 if (buffer_locked(bh)) 355 __wait_on_buffer(bh); 356 } 357 358 static inline int trylock_buffer(struct buffer_head *bh) 359 { 360 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); 361 } 362 363 static inline void lock_buffer(struct buffer_head *bh) 364 { 365 might_sleep(); 366 if (!trylock_buffer(bh)) 367 __lock_buffer(bh); 368 } 369 370 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev, 371 sector_t block, 372 unsigned size) 373 { 374 return __getblk_gfp(bdev, block, size, 0); 375 } 376 377 static inline struct buffer_head *__getblk(struct block_device *bdev, 378 sector_t block, 379 unsigned size) 380 { 381 return __getblk_gfp(bdev, block, size, __GFP_MOVABLE); 382 } 383 384 /** 385 * __bread() - reads a specified block and returns the bh 386 * @bdev: the block_device to read from 387 * @block: number of block 388 * @size: size (in bytes) to read 389 * 390 * Reads a specified block, and returns buffer head that contains it. 391 * The page cache is allocated from movable area so that it can be migrated. 392 * It returns NULL if the block was unreadable. 393 */ 394 static inline struct buffer_head * 395 __bread(struct block_device *bdev, sector_t block, unsigned size) 396 { 397 return __bread_gfp(bdev, block, size, __GFP_MOVABLE); 398 } 399 400 bool block_dirty_folio(struct address_space *mapping, struct folio *folio); 401 402 #else /* CONFIG_BLOCK */ 403 404 static inline void buffer_init(void) {} 405 static inline bool try_to_free_buffers(struct folio *folio) { return true; } 406 static inline int inode_has_buffers(struct inode *inode) { return 0; } 407 static inline void invalidate_inode_buffers(struct inode *inode) {} 408 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 409 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 410 static inline void invalidate_bh_lrus_cpu(void) {} 411 static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; } 412 #define buffer_heads_over_limit 0 413 414 #endif /* CONFIG_BLOCK */ 415 #endif /* _LINUX_BUFFER_HEAD_H */ 416