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 <asm/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_Ordered, /* ordered write */ 36 BH_Eopnotsupp, /* operation not supported (barrier) */ 37 BH_Unwritten, /* Buffer is allocated on disk but not written */ 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_CACHE_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 }; 77 78 /* 79 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() 80 * and buffer_foo() functions. 81 */ 82 #define BUFFER_FNS(bit, name) \ 83 static inline void set_buffer_##name(struct buffer_head *bh) \ 84 { \ 85 set_bit(BH_##bit, &(bh)->b_state); \ 86 } \ 87 static inline void clear_buffer_##name(struct buffer_head *bh) \ 88 { \ 89 clear_bit(BH_##bit, &(bh)->b_state); \ 90 } \ 91 static inline int buffer_##name(const struct buffer_head *bh) \ 92 { \ 93 return test_bit(BH_##bit, &(bh)->b_state); \ 94 } 95 96 /* 97 * test_set_buffer_foo() and test_clear_buffer_foo() 98 */ 99 #define TAS_BUFFER_FNS(bit, name) \ 100 static inline int test_set_buffer_##name(struct buffer_head *bh) \ 101 { \ 102 return test_and_set_bit(BH_##bit, &(bh)->b_state); \ 103 } \ 104 static inline int test_clear_buffer_##name(struct buffer_head *bh) \ 105 { \ 106 return test_and_clear_bit(BH_##bit, &(bh)->b_state); \ 107 } \ 108 109 /* 110 * Emit the buffer bitops functions. Note that there are also functions 111 * of the form "mark_buffer_foo()". These are higher-level functions which 112 * do something in addition to setting a b_state bit. 113 */ 114 BUFFER_FNS(Uptodate, uptodate) 115 BUFFER_FNS(Dirty, dirty) 116 TAS_BUFFER_FNS(Dirty, dirty) 117 BUFFER_FNS(Lock, locked) 118 BUFFER_FNS(Req, req) 119 TAS_BUFFER_FNS(Req, req) 120 BUFFER_FNS(Mapped, mapped) 121 BUFFER_FNS(New, new) 122 BUFFER_FNS(Async_Read, async_read) 123 BUFFER_FNS(Async_Write, async_write) 124 BUFFER_FNS(Delay, delay) 125 BUFFER_FNS(Boundary, boundary) 126 BUFFER_FNS(Write_EIO, write_io_error) 127 BUFFER_FNS(Ordered, ordered) 128 BUFFER_FNS(Eopnotsupp, eopnotsupp) 129 BUFFER_FNS(Unwritten, unwritten) 130 131 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) 132 #define touch_buffer(bh) mark_page_accessed(bh->b_page) 133 134 /* If we *know* page->private refers to buffer_heads */ 135 #define page_buffers(page) \ 136 ({ \ 137 BUG_ON(!PagePrivate(page)); \ 138 ((struct buffer_head *)page_private(page)); \ 139 }) 140 #define page_has_buffers(page) PagePrivate(page) 141 142 /* 143 * Declarations 144 */ 145 146 void mark_buffer_dirty(struct buffer_head *bh); 147 void init_buffer(struct buffer_head *, bh_end_io_t *, void *); 148 void set_bh_page(struct buffer_head *bh, 149 struct page *page, unsigned long offset); 150 int try_to_free_buffers(struct page *); 151 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 152 int retry); 153 void create_empty_buffers(struct page *, unsigned long, 154 unsigned long b_state); 155 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 156 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 157 158 /* Things to do with buffers at mapping->private_list */ 159 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 160 int inode_has_buffers(struct inode *); 161 void invalidate_inode_buffers(struct inode *); 162 int remove_inode_buffers(struct inode *inode); 163 int sync_mapping_buffers(struct address_space *mapping); 164 void unmap_underlying_metadata(struct block_device *bdev, sector_t block); 165 166 void mark_buffer_async_write(struct buffer_head *bh); 167 void invalidate_bdev(struct block_device *); 168 int sync_blockdev(struct block_device *bdev); 169 void __wait_on_buffer(struct buffer_head *); 170 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 171 int fsync_bdev(struct block_device *); 172 struct super_block *freeze_bdev(struct block_device *); 173 void thaw_bdev(struct block_device *, struct super_block *); 174 int fsync_super(struct super_block *); 175 int fsync_no_super(struct block_device *); 176 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, 177 unsigned size); 178 struct buffer_head *__getblk(struct block_device *bdev, sector_t block, 179 unsigned size); 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(struct block_device *, sector_t block, unsigned size); 184 void invalidate_bh_lrus(void); 185 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 186 void free_buffer_head(struct buffer_head * bh); 187 void unlock_buffer(struct buffer_head *bh); 188 void __lock_buffer(struct buffer_head *bh); 189 void ll_rw_block(int, int, struct buffer_head * bh[]); 190 int sync_dirty_buffer(struct buffer_head *bh); 191 int submit_bh(int, struct buffer_head *); 192 void write_boundary_block(struct block_device *bdev, 193 sector_t bblock, unsigned blocksize); 194 int bh_uptodate_or_lock(struct buffer_head *bh); 195 int bh_submit_read(struct buffer_head *bh); 196 197 extern int buffer_heads_over_limit; 198 199 /* 200 * Generic address_space_operations implementations for buffer_head-backed 201 * address_spaces. 202 */ 203 void block_invalidatepage(struct page *page, unsigned long offset); 204 int block_write_full_page(struct page *page, get_block_t *get_block, 205 struct writeback_control *wbc); 206 int block_read_full_page(struct page*, get_block_t*); 207 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, 208 unsigned long from); 209 int block_write_begin(struct file *, struct address_space *, 210 loff_t, unsigned, unsigned, 211 struct page **, void **, get_block_t*); 212 int block_write_end(struct file *, struct address_space *, 213 loff_t, unsigned, unsigned, 214 struct page *, void *); 215 int generic_write_end(struct file *, struct address_space *, 216 loff_t, unsigned, unsigned, 217 struct page *, void *); 218 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to); 219 int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*); 220 int cont_write_begin(struct file *, struct address_space *, loff_t, 221 unsigned, unsigned, struct page **, void **, 222 get_block_t *, loff_t *); 223 int generic_cont_expand_simple(struct inode *inode, loff_t size); 224 int block_commit_write(struct page *page, unsigned from, unsigned to); 225 int block_page_mkwrite(struct vm_area_struct *vma, struct page *page, 226 get_block_t get_block); 227 void block_sync_page(struct page *); 228 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 229 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 230 int file_fsync(struct file *, struct dentry *, int); 231 int nobh_write_begin(struct file *, struct address_space *, 232 loff_t, unsigned, unsigned, 233 struct page **, void **, get_block_t*); 234 int nobh_write_end(struct file *, struct address_space *, 235 loff_t, unsigned, unsigned, 236 struct page *, void *); 237 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *); 238 int nobh_writepage(struct page *page, get_block_t *get_block, 239 struct writeback_control *wbc); 240 241 void buffer_init(void); 242 243 /* 244 * inline definitions 245 */ 246 247 static inline void attach_page_buffers(struct page *page, 248 struct buffer_head *head) 249 { 250 page_cache_get(page); 251 SetPagePrivate(page); 252 set_page_private(page, (unsigned long)head); 253 } 254 255 static inline void get_bh(struct buffer_head *bh) 256 { 257 atomic_inc(&bh->b_count); 258 } 259 260 static inline void put_bh(struct buffer_head *bh) 261 { 262 smp_mb__before_atomic_dec(); 263 atomic_dec(&bh->b_count); 264 } 265 266 static inline void brelse(struct buffer_head *bh) 267 { 268 if (bh) 269 __brelse(bh); 270 } 271 272 static inline void bforget(struct buffer_head *bh) 273 { 274 if (bh) 275 __bforget(bh); 276 } 277 278 static inline struct buffer_head * 279 sb_bread(struct super_block *sb, sector_t block) 280 { 281 return __bread(sb->s_bdev, block, sb->s_blocksize); 282 } 283 284 static inline void 285 sb_breadahead(struct super_block *sb, sector_t block) 286 { 287 __breadahead(sb->s_bdev, block, sb->s_blocksize); 288 } 289 290 static inline struct buffer_head * 291 sb_getblk(struct super_block *sb, sector_t block) 292 { 293 return __getblk(sb->s_bdev, block, sb->s_blocksize); 294 } 295 296 static inline struct buffer_head * 297 sb_find_get_block(struct super_block *sb, sector_t block) 298 { 299 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 300 } 301 302 static inline void 303 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 304 { 305 set_buffer_mapped(bh); 306 bh->b_bdev = sb->s_bdev; 307 bh->b_blocknr = block; 308 bh->b_size = sb->s_blocksize; 309 } 310 311 /* 312 * Calling wait_on_buffer() for a zero-ref buffer is illegal, so we call into 313 * __wait_on_buffer() just to trip a debug check. Because debug code in inline 314 * functions is bloaty. 315 */ 316 static inline void wait_on_buffer(struct buffer_head *bh) 317 { 318 might_sleep(); 319 if (buffer_locked(bh) || atomic_read(&bh->b_count) == 0) 320 __wait_on_buffer(bh); 321 } 322 323 static inline int trylock_buffer(struct buffer_head *bh) 324 { 325 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); 326 } 327 328 static inline void lock_buffer(struct buffer_head *bh) 329 { 330 might_sleep(); 331 if (!trylock_buffer(bh)) 332 __lock_buffer(bh); 333 } 334 335 extern int __set_page_dirty_buffers(struct page *page); 336 337 #else /* CONFIG_BLOCK */ 338 339 static inline void buffer_init(void) {} 340 static inline int try_to_free_buffers(struct page *page) { return 1; } 341 static inline int sync_blockdev(struct block_device *bdev) { return 0; } 342 static inline int inode_has_buffers(struct inode *inode) { return 0; } 343 static inline void invalidate_inode_buffers(struct inode *inode) {} 344 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 345 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 346 static inline void invalidate_bdev(struct block_device *bdev) {} 347 348 349 #endif /* CONFIG_BLOCK */ 350 #endif /* _LINUX_BUFFER_HEAD_H */ 351