1 /* 2 * include/linux/buffer_head.h 3 * 4 * Everything to do with buffer_heads. 5 */ 6 7 #ifndef _LINUX_BUFFER_HEAD_H 8 #define _LINUX_BUFFER_HEAD_H 9 10 #include <linux/types.h> 11 #include <linux/fs.h> 12 #include <linux/linkage.h> 13 #include <linux/pagemap.h> 14 #include <linux/wait.h> 15 #include <linux/atomic.h> 16 17 #ifdef CONFIG_BLOCK 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 BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise 25 * IO completion of other buffers in the page 26 */ 27 28 BH_Mapped, /* Has a disk mapping */ 29 BH_New, /* Disk mapping was newly created by get_block */ 30 BH_Async_Read, /* Is under end_buffer_async_read I/O */ 31 BH_Async_Write, /* Is under end_buffer_async_write I/O */ 32 BH_Delay, /* Buffer is not yet allocated on disk */ 33 BH_Boundary, /* Block is followed by a discontiguity */ 34 BH_Write_EIO, /* I/O error on write */ 35 BH_Unwritten, /* Buffer is allocated on disk but not written */ 36 BH_Quiet, /* Buffer Error Prinks to be quiet */ 37 BH_Meta, /* Buffer contains metadata */ 38 BH_Prio, /* Buffer should be submitted with REQ_PRIO */ 39 BH_Defer_Completion, /* Defer AIO completion to workqueue */ 40 41 BH_PrivateStart,/* not a state bit, but the first bit available 42 * for private allocation by other entities 43 */ 44 }; 45 46 #define MAX_BUF_PER_PAGE (PAGE_SIZE / 512) 47 48 struct page; 49 struct buffer_head; 50 struct address_space; 51 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate); 52 53 /* 54 * Historically, a buffer_head was used to map a single block 55 * within a page, and of course as the unit of I/O through the 56 * filesystem and block layers. Nowadays the basic I/O unit 57 * is the bio, and buffer_heads are used for extracting block 58 * mappings (via a get_block_t call), for tracking state within 59 * a page (via a page_mapping) and for wrapping bio submission 60 * for backward compatibility reasons (e.g. submit_bh). 61 */ 62 struct buffer_head { 63 unsigned long b_state; /* buffer state bitmap (see above) */ 64 struct buffer_head *b_this_page;/* circular list of page's buffers */ 65 struct page *b_page; /* the page this bh is mapped to */ 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 }; 79 80 /* 81 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() 82 * and buffer_foo() functions. 83 */ 84 #define BUFFER_FNS(bit, name) \ 85 static __always_inline void set_buffer_##name(struct buffer_head *bh) \ 86 { \ 87 set_bit(BH_##bit, &(bh)->b_state); \ 88 } \ 89 static __always_inline void clear_buffer_##name(struct buffer_head *bh) \ 90 { \ 91 clear_bit(BH_##bit, &(bh)->b_state); \ 92 } \ 93 static __always_inline int buffer_##name(const struct buffer_head *bh) \ 94 { \ 95 return test_bit(BH_##bit, &(bh)->b_state); \ 96 } 97 98 /* 99 * test_set_buffer_foo() and test_clear_buffer_foo() 100 */ 101 #define TAS_BUFFER_FNS(bit, name) \ 102 static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \ 103 { \ 104 return test_and_set_bit(BH_##bit, &(bh)->b_state); \ 105 } \ 106 static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \ 107 { \ 108 return test_and_clear_bit(BH_##bit, &(bh)->b_state); \ 109 } \ 110 111 /* 112 * Emit the buffer bitops functions. Note that there are also functions 113 * of the form "mark_buffer_foo()". These are higher-level functions which 114 * do something in addition to setting a b_state bit. 115 */ 116 BUFFER_FNS(Uptodate, uptodate) 117 BUFFER_FNS(Dirty, dirty) 118 TAS_BUFFER_FNS(Dirty, dirty) 119 BUFFER_FNS(Lock, locked) 120 BUFFER_FNS(Req, req) 121 TAS_BUFFER_FNS(Req, req) 122 BUFFER_FNS(Mapped, mapped) 123 BUFFER_FNS(New, new) 124 BUFFER_FNS(Async_Read, async_read) 125 BUFFER_FNS(Async_Write, async_write) 126 BUFFER_FNS(Delay, delay) 127 BUFFER_FNS(Boundary, boundary) 128 BUFFER_FNS(Write_EIO, write_io_error) 129 BUFFER_FNS(Unwritten, unwritten) 130 BUFFER_FNS(Meta, meta) 131 BUFFER_FNS(Prio, prio) 132 BUFFER_FNS(Defer_Completion, defer_completion) 133 134 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) 135 136 /* If we *know* page->private refers to buffer_heads */ 137 #define page_buffers(page) \ 138 ({ \ 139 BUG_ON(!PagePrivate(page)); \ 140 ((struct buffer_head *)page_private(page)); \ 141 }) 142 #define page_has_buffers(page) PagePrivate(page) 143 144 void buffer_check_dirty_writeback(struct page *page, 145 bool *dirty, bool *writeback); 146 147 /* 148 * Declarations 149 */ 150 151 void mark_buffer_dirty(struct buffer_head *bh); 152 void init_buffer(struct buffer_head *, bh_end_io_t *, void *); 153 void touch_buffer(struct buffer_head *bh); 154 void set_bh_page(struct buffer_head *bh, 155 struct page *page, unsigned long offset); 156 int try_to_free_buffers(struct page *); 157 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 158 int retry); 159 void create_empty_buffers(struct page *, unsigned long, 160 unsigned long b_state); 161 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 162 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 163 void end_buffer_async_write(struct buffer_head *bh, int uptodate); 164 165 /* Things to do with buffers at mapping->private_list */ 166 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 167 int inode_has_buffers(struct inode *); 168 void invalidate_inode_buffers(struct inode *); 169 int remove_inode_buffers(struct inode *inode); 170 int sync_mapping_buffers(struct address_space *mapping); 171 void unmap_underlying_metadata(struct block_device *bdev, sector_t block); 172 173 void mark_buffer_async_write(struct buffer_head *bh); 174 void __wait_on_buffer(struct buffer_head *); 175 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 176 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, 177 unsigned size); 178 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block, 179 unsigned size, gfp_t gfp); 180 void __brelse(struct buffer_head *); 181 void __bforget(struct buffer_head *); 182 void __breadahead(struct block_device *, sector_t block, unsigned int size); 183 struct buffer_head *__bread_gfp(struct block_device *, 184 sector_t block, unsigned size, gfp_t gfp); 185 void invalidate_bh_lrus(void); 186 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 187 void free_buffer_head(struct buffer_head * bh); 188 void unlock_buffer(struct buffer_head *bh); 189 void __lock_buffer(struct buffer_head *bh); 190 void ll_rw_block(int, int, struct buffer_head * bh[]); 191 int sync_dirty_buffer(struct buffer_head *bh); 192 int __sync_dirty_buffer(struct buffer_head *bh, int rw); 193 void write_dirty_buffer(struct buffer_head *bh, int rw); 194 int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags); 195 int submit_bh(int, struct buffer_head *); 196 void write_boundary_block(struct block_device *bdev, 197 sector_t bblock, unsigned blocksize); 198 int bh_uptodate_or_lock(struct buffer_head *bh); 199 int bh_submit_read(struct buffer_head *bh); 200 201 extern int buffer_heads_over_limit; 202 203 /* 204 * Generic address_space_operations implementations for buffer_head-backed 205 * address_spaces. 206 */ 207 void block_invalidatepage(struct page *page, unsigned int offset, 208 unsigned int length); 209 int block_write_full_page(struct page *page, get_block_t *get_block, 210 struct writeback_control *wbc); 211 int block_read_full_page(struct page*, get_block_t*); 212 int block_is_partially_uptodate(struct page *page, unsigned long from, 213 unsigned long count); 214 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, 215 unsigned flags, struct page **pagep, get_block_t *get_block); 216 int __block_write_begin(struct page *page, loff_t pos, unsigned len, 217 get_block_t *get_block); 218 int block_write_end(struct file *, struct address_space *, 219 loff_t, unsigned, unsigned, 220 struct page *, void *); 221 int generic_write_end(struct file *, struct address_space *, 222 loff_t, unsigned, unsigned, 223 struct page *, void *); 224 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to); 225 int cont_write_begin(struct file *, struct address_space *, loff_t, 226 unsigned, unsigned, struct page **, void **, 227 get_block_t *, loff_t *); 228 int generic_cont_expand_simple(struct inode *inode, loff_t size); 229 int block_commit_write(struct page *page, unsigned from, unsigned to); 230 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 231 get_block_t get_block); 232 /* Convert errno to return value from ->page_mkwrite() call */ 233 static inline int block_page_mkwrite_return(int err) 234 { 235 if (err == 0) 236 return VM_FAULT_LOCKED; 237 if (err == -EFAULT) 238 return VM_FAULT_NOPAGE; 239 if (err == -ENOMEM) 240 return VM_FAULT_OOM; 241 if (err == -EAGAIN) 242 return VM_FAULT_RETRY; 243 /* -ENOSPC, -EDQUOT, -EIO ... */ 244 return VM_FAULT_SIGBUS; 245 } 246 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 247 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 248 int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned, 249 struct page **, void **, get_block_t*); 250 int nobh_write_end(struct file *, struct address_space *, 251 loff_t, unsigned, unsigned, 252 struct page *, void *); 253 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *); 254 int nobh_writepage(struct page *page, get_block_t *get_block, 255 struct writeback_control *wbc); 256 257 void buffer_init(void); 258 259 /* 260 * inline definitions 261 */ 262 263 static inline void attach_page_buffers(struct page *page, 264 struct buffer_head *head) 265 { 266 get_page(page); 267 SetPagePrivate(page); 268 set_page_private(page, (unsigned long)head); 269 } 270 271 static inline void get_bh(struct buffer_head *bh) 272 { 273 atomic_inc(&bh->b_count); 274 } 275 276 static inline void put_bh(struct buffer_head *bh) 277 { 278 smp_mb__before_atomic(); 279 atomic_dec(&bh->b_count); 280 } 281 282 static inline void brelse(struct buffer_head *bh) 283 { 284 if (bh) 285 __brelse(bh); 286 } 287 288 static inline void bforget(struct buffer_head *bh) 289 { 290 if (bh) 291 __bforget(bh); 292 } 293 294 static inline struct buffer_head * 295 sb_bread(struct super_block *sb, sector_t block) 296 { 297 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 298 } 299 300 static inline struct buffer_head * 301 sb_bread_unmovable(struct super_block *sb, sector_t block) 302 { 303 return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0); 304 } 305 306 static inline void 307 sb_breadahead(struct super_block *sb, sector_t block) 308 { 309 __breadahead(sb->s_bdev, block, sb->s_blocksize); 310 } 311 312 static inline struct buffer_head * 313 sb_getblk(struct super_block *sb, sector_t block) 314 { 315 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE); 316 } 317 318 319 static inline struct buffer_head * 320 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp) 321 { 322 return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp); 323 } 324 325 static inline struct buffer_head * 326 sb_find_get_block(struct super_block *sb, sector_t block) 327 { 328 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 329 } 330 331 static inline void 332 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 333 { 334 set_buffer_mapped(bh); 335 bh->b_bdev = sb->s_bdev; 336 bh->b_blocknr = block; 337 bh->b_size = sb->s_blocksize; 338 } 339 340 static inline void wait_on_buffer(struct buffer_head *bh) 341 { 342 might_sleep(); 343 if (buffer_locked(bh)) 344 __wait_on_buffer(bh); 345 } 346 347 static inline int trylock_buffer(struct buffer_head *bh) 348 { 349 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); 350 } 351 352 static inline void lock_buffer(struct buffer_head *bh) 353 { 354 might_sleep(); 355 if (!trylock_buffer(bh)) 356 __lock_buffer(bh); 357 } 358 359 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev, 360 sector_t block, 361 unsigned size) 362 { 363 return __getblk_gfp(bdev, block, size, 0); 364 } 365 366 static inline struct buffer_head *__getblk(struct block_device *bdev, 367 sector_t block, 368 unsigned size) 369 { 370 return __getblk_gfp(bdev, block, size, __GFP_MOVABLE); 371 } 372 373 /** 374 * __bread() - reads a specified block and returns the bh 375 * @bdev: the block_device to read from 376 * @block: number of block 377 * @size: size (in bytes) to read 378 * 379 * Reads a specified block, and returns buffer head that contains it. 380 * The page cache is allocated from movable area so that it can be migrated. 381 * It returns NULL if the block was unreadable. 382 */ 383 static inline struct buffer_head * 384 __bread(struct block_device *bdev, sector_t block, unsigned size) 385 { 386 return __bread_gfp(bdev, block, size, __GFP_MOVABLE); 387 } 388 389 extern int __set_page_dirty_buffers(struct page *page); 390 391 #else /* CONFIG_BLOCK */ 392 393 static inline void buffer_init(void) {} 394 static inline int try_to_free_buffers(struct page *page) { return 1; } 395 static inline int inode_has_buffers(struct inode *inode) { return 0; } 396 static inline void invalidate_inode_buffers(struct inode *inode) {} 397 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 398 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 399 400 #endif /* CONFIG_BLOCK */ 401 #endif /* _LINUX_BUFFER_HEAD_H */ 402