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) 147 148 void buffer_check_dirty_writeback(struct page *page, 149 bool *dirty, bool *writeback); 150 151 /* 152 * Declarations 153 */ 154 155 void mark_buffer_dirty(struct buffer_head *bh); 156 void mark_buffer_write_io_error(struct buffer_head *bh); 157 void touch_buffer(struct buffer_head *bh); 158 void set_bh_page(struct buffer_head *bh, 159 struct page *page, unsigned long offset); 160 int try_to_free_buffers(struct page *); 161 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 162 bool retry); 163 void create_empty_buffers(struct page *, unsigned long, 164 unsigned long b_state); 165 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 166 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 167 void end_buffer_async_write(struct buffer_head *bh, int uptodate); 168 169 /* Things to do with buffers at mapping->private_list */ 170 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 171 int inode_has_buffers(struct inode *); 172 void invalidate_inode_buffers(struct inode *); 173 int remove_inode_buffers(struct inode *inode); 174 int sync_mapping_buffers(struct address_space *mapping); 175 void clean_bdev_aliases(struct block_device *bdev, sector_t block, 176 sector_t len); 177 static inline void clean_bdev_bh_alias(struct buffer_head *bh) 178 { 179 clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1); 180 } 181 182 void mark_buffer_async_write(struct buffer_head *bh); 183 void __wait_on_buffer(struct buffer_head *); 184 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 185 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, 186 unsigned size); 187 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block, 188 unsigned size, gfp_t gfp); 189 void __brelse(struct buffer_head *); 190 void __bforget(struct buffer_head *); 191 void __breadahead(struct block_device *, sector_t block, unsigned int size); 192 void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size, 193 gfp_t gfp); 194 struct buffer_head *__bread_gfp(struct block_device *, 195 sector_t block, unsigned size, gfp_t gfp); 196 void invalidate_bh_lrus(void); 197 void invalidate_bh_lrus_cpu(int cpu); 198 bool has_bh_in_lru(int cpu, void *dummy); 199 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 200 void free_buffer_head(struct buffer_head * bh); 201 void unlock_buffer(struct buffer_head *bh); 202 void __lock_buffer(struct buffer_head *bh); 203 void ll_rw_block(int, int, int, struct buffer_head * bh[]); 204 int sync_dirty_buffer(struct buffer_head *bh); 205 int __sync_dirty_buffer(struct buffer_head *bh, int op_flags); 206 void write_dirty_buffer(struct buffer_head *bh, int op_flags); 207 int submit_bh(int, int, struct buffer_head *); 208 void write_boundary_block(struct block_device *bdev, 209 sector_t bblock, unsigned blocksize); 210 int bh_uptodate_or_lock(struct buffer_head *bh); 211 int bh_submit_read(struct buffer_head *bh); 212 213 extern int buffer_heads_over_limit; 214 215 /* 216 * Generic address_space_operations implementations for buffer_head-backed 217 * address_spaces. 218 */ 219 void block_invalidatepage(struct page *page, unsigned int offset, 220 unsigned int 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_page(struct page*, get_block_t*); 227 int block_is_partially_uptodate(struct page *page, unsigned long from, 228 unsigned long count); 229 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, 230 unsigned flags, 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, 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 int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned, 263 struct page **, void **, get_block_t*); 264 int nobh_write_end(struct file *, struct address_space *, 265 loff_t, unsigned, unsigned, 266 struct page *, void *); 267 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *); 268 int nobh_writepage(struct page *page, get_block_t *get_block, 269 struct writeback_control *wbc); 270 271 void buffer_init(void); 272 273 /* 274 * inline definitions 275 */ 276 277 static inline void get_bh(struct buffer_head *bh) 278 { 279 atomic_inc(&bh->b_count); 280 } 281 282 static inline void put_bh(struct buffer_head *bh) 283 { 284 smp_mb__before_atomic(); 285 atomic_dec(&bh->b_count); 286 } 287 288 static inline void brelse(struct buffer_head *bh) 289 { 290 if (bh) 291 __brelse(bh); 292 } 293 294 static inline void bforget(struct buffer_head *bh) 295 { 296 if (bh) 297 __bforget(bh); 298 } 299 300 static inline struct buffer_head * 301 sb_bread(struct super_block *sb, sector_t block) 302 { 303 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 304 } 305 306 static inline struct buffer_head * 307 sb_bread_unmovable(struct super_block *sb, sector_t block) 308 { 309 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0); 310 } 311 312 static inline void 313 sb_breadahead(struct super_block *sb, sector_t block) 314 { 315 __breadahead(sb->s_bdev, block, sb->s_blocksize); 316 } 317 318 static inline void 319 sb_breadahead_unmovable(struct super_block *sb, sector_t block) 320 { 321 __breadahead_gfp(sb->s_bdev, block, sb->s_blocksize, 0); 322 } 323 324 static inline struct buffer_head * 325 sb_getblk(struct super_block *sb, sector_t block) 326 { 327 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 328 } 329 330 331 static inline struct buffer_head * 332 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp) 333 { 334 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp); 335 } 336 337 static inline struct buffer_head * 338 sb_find_get_block(struct super_block *sb, sector_t block) 339 { 340 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 341 } 342 343 static inline void 344 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 345 { 346 set_buffer_mapped(bh); 347 bh->b_bdev = sb->s_bdev; 348 bh->b_blocknr = block; 349 bh->b_size = sb->s_blocksize; 350 } 351 352 static inline void wait_on_buffer(struct buffer_head *bh) 353 { 354 might_sleep(); 355 if (buffer_locked(bh)) 356 __wait_on_buffer(bh); 357 } 358 359 static inline int trylock_buffer(struct buffer_head *bh) 360 { 361 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); 362 } 363 364 static inline void lock_buffer(struct buffer_head *bh) 365 { 366 might_sleep(); 367 if (!trylock_buffer(bh)) 368 __lock_buffer(bh); 369 } 370 371 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev, 372 sector_t block, 373 unsigned size) 374 { 375 return __getblk_gfp(bdev, block, size, 0); 376 } 377 378 static inline struct buffer_head *__getblk(struct block_device *bdev, 379 sector_t block, 380 unsigned size) 381 { 382 return __getblk_gfp(bdev, block, size, __GFP_MOVABLE); 383 } 384 385 /** 386 * __bread() - reads a specified block and returns the bh 387 * @bdev: the block_device to read from 388 * @block: number of block 389 * @size: size (in bytes) to read 390 * 391 * Reads a specified block, and returns buffer head that contains it. 392 * The page cache is allocated from movable area so that it can be migrated. 393 * It returns NULL if the block was unreadable. 394 */ 395 static inline struct buffer_head * 396 __bread(struct block_device *bdev, sector_t block, unsigned size) 397 { 398 return __bread_gfp(bdev, block, size, __GFP_MOVABLE); 399 } 400 401 extern int __set_page_dirty_buffers(struct page *page); 402 403 #else /* CONFIG_BLOCK */ 404 405 static inline void buffer_init(void) {} 406 static inline int try_to_free_buffers(struct page *page) { return 1; } 407 static inline int inode_has_buffers(struct inode *inode) { return 0; } 408 static inline void invalidate_inode_buffers(struct inode *inode) {} 409 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 410 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 411 static inline void invalidate_bh_lrus_cpu(int cpu) {} 412 static inline bool has_bh_in_lru(int cpu, void *dummy) { return 0; } 413 #define buffer_heads_over_limit 0 414 415 #endif /* CONFIG_BLOCK */ 416 #endif /* _LINUX_BUFFER_HEAD_H */ 417