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 BH_Quiet, /* Buffer Error Prinks to be quiet */ 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_CACHE_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 }; 78 79 /* 80 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() 81 * and buffer_foo() functions. 82 */ 83 #define BUFFER_FNS(bit, name) \ 84 static inline void set_buffer_##name(struct buffer_head *bh) \ 85 { \ 86 set_bit(BH_##bit, &(bh)->b_state); \ 87 } \ 88 static inline void clear_buffer_##name(struct buffer_head *bh) \ 89 { \ 90 clear_bit(BH_##bit, &(bh)->b_state); \ 91 } \ 92 static inline int buffer_##name(const struct buffer_head *bh) \ 93 { \ 94 return test_bit(BH_##bit, &(bh)->b_state); \ 95 } 96 97 /* 98 * test_set_buffer_foo() and test_clear_buffer_foo() 99 */ 100 #define TAS_BUFFER_FNS(bit, name) \ 101 static inline int test_set_buffer_##name(struct buffer_head *bh) \ 102 { \ 103 return test_and_set_bit(BH_##bit, &(bh)->b_state); \ 104 } \ 105 static inline int test_clear_buffer_##name(struct buffer_head *bh) \ 106 { \ 107 return test_and_clear_bit(BH_##bit, &(bh)->b_state); \ 108 } \ 109 110 /* 111 * Emit the buffer bitops functions. Note that there are also functions 112 * of the form "mark_buffer_foo()". These are higher-level functions which 113 * do something in addition to setting a b_state bit. 114 */ 115 BUFFER_FNS(Uptodate, uptodate) 116 BUFFER_FNS(Dirty, dirty) 117 TAS_BUFFER_FNS(Dirty, dirty) 118 BUFFER_FNS(Lock, locked) 119 BUFFER_FNS(Req, req) 120 TAS_BUFFER_FNS(Req, req) 121 BUFFER_FNS(Mapped, mapped) 122 BUFFER_FNS(New, new) 123 BUFFER_FNS(Async_Read, async_read) 124 BUFFER_FNS(Async_Write, async_write) 125 BUFFER_FNS(Delay, delay) 126 BUFFER_FNS(Boundary, boundary) 127 BUFFER_FNS(Write_EIO, write_io_error) 128 BUFFER_FNS(Ordered, ordered) 129 BUFFER_FNS(Eopnotsupp, eopnotsupp) 130 BUFFER_FNS(Unwritten, unwritten) 131 132 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) 133 #define touch_buffer(bh) mark_page_accessed(bh->b_page) 134 135 /* If we *know* page->private refers to buffer_heads */ 136 #define page_buffers(page) \ 137 ({ \ 138 BUG_ON(!PagePrivate(page)); \ 139 ((struct buffer_head *)page_private(page)); \ 140 }) 141 #define page_has_buffers(page) PagePrivate(page) 142 143 /* 144 * Declarations 145 */ 146 147 void mark_buffer_dirty(struct buffer_head *bh); 148 void init_buffer(struct buffer_head *, bh_end_io_t *, void *); 149 void set_bh_page(struct buffer_head *bh, 150 struct page *page, unsigned long offset); 151 int try_to_free_buffers(struct page *); 152 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 153 int retry); 154 void create_empty_buffers(struct page *, unsigned long, 155 unsigned long b_state); 156 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 157 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 158 void end_buffer_async_write(struct buffer_head *bh, int uptodate); 159 160 /* Things to do with buffers at mapping->private_list */ 161 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 162 int inode_has_buffers(struct inode *); 163 void invalidate_inode_buffers(struct inode *); 164 int remove_inode_buffers(struct inode *inode); 165 int sync_mapping_buffers(struct address_space *mapping); 166 void unmap_underlying_metadata(struct block_device *bdev, sector_t block); 167 168 void mark_buffer_async_write(struct buffer_head *bh); 169 void __wait_on_buffer(struct buffer_head *); 170 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 171 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, 172 unsigned size); 173 struct buffer_head *__getblk(struct block_device *bdev, sector_t block, 174 unsigned size); 175 void __brelse(struct buffer_head *); 176 void __bforget(struct buffer_head *); 177 void __breadahead(struct block_device *, sector_t block, unsigned int size); 178 struct buffer_head *__bread(struct block_device *, sector_t block, unsigned size); 179 void invalidate_bh_lrus(void); 180 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 181 void free_buffer_head(struct buffer_head * bh); 182 void unlock_buffer(struct buffer_head *bh); 183 void __lock_buffer(struct buffer_head *bh); 184 void ll_rw_block(int, int, struct buffer_head * bh[]); 185 int sync_dirty_buffer(struct buffer_head *bh); 186 int submit_bh(int, struct buffer_head *); 187 void write_boundary_block(struct block_device *bdev, 188 sector_t bblock, unsigned blocksize); 189 int bh_uptodate_or_lock(struct buffer_head *bh); 190 int bh_submit_read(struct buffer_head *bh); 191 192 extern int buffer_heads_over_limit; 193 194 /* 195 * Generic address_space_operations implementations for buffer_head-backed 196 * address_spaces. 197 */ 198 void block_invalidatepage(struct page *page, unsigned long offset); 199 int block_write_full_page(struct page *page, get_block_t *get_block, 200 struct writeback_control *wbc); 201 int block_write_full_page_endio(struct page *page, get_block_t *get_block, 202 struct writeback_control *wbc, bh_end_io_t *handler); 203 int block_read_full_page(struct page*, get_block_t*); 204 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, 205 unsigned long from); 206 int block_write_begin(struct file *, struct address_space *, 207 loff_t, unsigned, unsigned, 208 struct page **, void **, get_block_t*); 209 int block_write_end(struct file *, struct address_space *, 210 loff_t, unsigned, unsigned, 211 struct page *, void *); 212 int generic_write_end(struct file *, struct address_space *, 213 loff_t, unsigned, unsigned, 214 struct page *, void *); 215 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to); 216 int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*); 217 int cont_write_begin(struct file *, struct address_space *, loff_t, 218 unsigned, unsigned, struct page **, void **, 219 get_block_t *, loff_t *); 220 int generic_cont_expand_simple(struct inode *inode, loff_t size); 221 int block_commit_write(struct page *page, unsigned from, unsigned to); 222 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 223 get_block_t get_block); 224 void block_sync_page(struct page *); 225 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 226 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 227 int file_fsync(struct file *, struct dentry *, int); 228 int nobh_write_begin(struct file *, struct address_space *, 229 loff_t, unsigned, unsigned, 230 struct page **, void **, get_block_t*); 231 int nobh_write_end(struct file *, struct address_space *, 232 loff_t, unsigned, unsigned, 233 struct page *, void *); 234 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *); 235 int nobh_writepage(struct page *page, get_block_t *get_block, 236 struct writeback_control *wbc); 237 238 void buffer_init(void); 239 240 /* 241 * inline definitions 242 */ 243 244 static inline void attach_page_buffers(struct page *page, 245 struct buffer_head *head) 246 { 247 page_cache_get(page); 248 SetPagePrivate(page); 249 set_page_private(page, (unsigned long)head); 250 } 251 252 static inline void get_bh(struct buffer_head *bh) 253 { 254 atomic_inc(&bh->b_count); 255 } 256 257 static inline void put_bh(struct buffer_head *bh) 258 { 259 smp_mb__before_atomic_dec(); 260 atomic_dec(&bh->b_count); 261 } 262 263 static inline void brelse(struct buffer_head *bh) 264 { 265 if (bh) 266 __brelse(bh); 267 } 268 269 static inline void bforget(struct buffer_head *bh) 270 { 271 if (bh) 272 __bforget(bh); 273 } 274 275 static inline struct buffer_head * 276 sb_bread(struct super_block *sb, sector_t block) 277 { 278 return __bread(sb->s_bdev, block, sb->s_blocksize); 279 } 280 281 static inline void 282 sb_breadahead(struct super_block *sb, sector_t block) 283 { 284 __breadahead(sb->s_bdev, block, sb->s_blocksize); 285 } 286 287 static inline struct buffer_head * 288 sb_getblk(struct super_block *sb, sector_t block) 289 { 290 return __getblk(sb->s_bdev, block, sb->s_blocksize); 291 } 292 293 static inline struct buffer_head * 294 sb_find_get_block(struct super_block *sb, sector_t block) 295 { 296 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 297 } 298 299 static inline void 300 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 301 { 302 set_buffer_mapped(bh); 303 bh->b_bdev = sb->s_bdev; 304 bh->b_blocknr = block; 305 bh->b_size = sb->s_blocksize; 306 } 307 308 /* 309 * Calling wait_on_buffer() for a zero-ref buffer is illegal, so we call into 310 * __wait_on_buffer() just to trip a debug check. Because debug code in inline 311 * functions is bloaty. 312 */ 313 static inline void wait_on_buffer(struct buffer_head *bh) 314 { 315 might_sleep(); 316 if (buffer_locked(bh) || atomic_read(&bh->b_count) == 0) 317 __wait_on_buffer(bh); 318 } 319 320 static inline int trylock_buffer(struct buffer_head *bh) 321 { 322 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); 323 } 324 325 static inline void lock_buffer(struct buffer_head *bh) 326 { 327 might_sleep(); 328 if (!trylock_buffer(bh)) 329 __lock_buffer(bh); 330 } 331 332 extern int __set_page_dirty_buffers(struct page *page); 333 334 #else /* CONFIG_BLOCK */ 335 336 static inline void buffer_init(void) {} 337 static inline int try_to_free_buffers(struct page *page) { return 1; } 338 static inline int inode_has_buffers(struct inode *inode) { return 0; } 339 static inline void invalidate_inode_buffers(struct inode *inode) {} 340 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 341 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 342 343 #endif /* CONFIG_BLOCK */ 344 #endif /* _LINUX_BUFFER_HEAD_H */ 345