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 TAS_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 FASTCALL(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); 158 159 /* Things to do with buffers at mapping->private_list */ 160 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 161 int inode_has_buffers(struct inode *); 162 void invalidate_inode_buffers(struct inode *); 163 int remove_inode_buffers(struct inode *inode); 164 int sync_mapping_buffers(struct address_space *mapping); 165 void unmap_underlying_metadata(struct block_device *bdev, sector_t block); 166 167 void mark_buffer_async_write(struct buffer_head *bh); 168 void invalidate_bdev(struct block_device *, int); 169 int sync_blockdev(struct block_device *bdev); 170 void __wait_on_buffer(struct buffer_head *); 171 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 172 int fsync_bdev(struct block_device *); 173 struct super_block *freeze_bdev(struct block_device *); 174 void thaw_bdev(struct block_device *, struct super_block *); 175 int fsync_super(struct super_block *); 176 int fsync_no_super(struct block_device *); 177 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, 178 unsigned size); 179 struct buffer_head *__getblk(struct block_device *bdev, sector_t block, 180 unsigned size); 181 void __brelse(struct buffer_head *); 182 void __bforget(struct buffer_head *); 183 void __breadahead(struct block_device *, sector_t block, unsigned int size); 184 struct buffer_head *__bread(struct block_device *, sector_t block, unsigned size); 185 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 186 void free_buffer_head(struct buffer_head * bh); 187 void FASTCALL(unlock_buffer(struct buffer_head *bh)); 188 void FASTCALL(__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); 194 195 extern int buffer_heads_over_limit; 196 197 /* 198 * Generic address_space_operations implementations for buffer_head-backed 199 * address_spaces. 200 */ 201 void block_invalidatepage(struct page *page, unsigned long offset); 202 int block_write_full_page(struct page *page, get_block_t *get_block, 203 struct writeback_control *wbc); 204 int block_read_full_page(struct page*, get_block_t*); 205 int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*); 206 int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*, 207 loff_t *); 208 int generic_cont_expand(struct inode *inode, loff_t size); 209 int generic_cont_expand_simple(struct inode *inode, loff_t size); 210 int block_commit_write(struct page *page, unsigned from, unsigned to); 211 void block_sync_page(struct page *); 212 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 213 int generic_commit_write(struct file *, struct page *, unsigned, unsigned); 214 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 215 int file_fsync(struct file *, struct dentry *, int); 216 int nobh_prepare_write(struct page*, unsigned, unsigned, get_block_t*); 217 int nobh_commit_write(struct file *, struct page *, unsigned, unsigned); 218 int nobh_truncate_page(struct address_space *, loff_t); 219 int nobh_writepage(struct page *page, get_block_t *get_block, 220 struct writeback_control *wbc); 221 222 void buffer_init(void); 223 224 /* 225 * inline definitions 226 */ 227 228 static inline void attach_page_buffers(struct page *page, 229 struct buffer_head *head) 230 { 231 page_cache_get(page); 232 SetPagePrivate(page); 233 set_page_private(page, (unsigned long)head); 234 } 235 236 static inline void get_bh(struct buffer_head *bh) 237 { 238 atomic_inc(&bh->b_count); 239 } 240 241 static inline void put_bh(struct buffer_head *bh) 242 { 243 smp_mb__before_atomic_dec(); 244 atomic_dec(&bh->b_count); 245 } 246 247 static inline void brelse(struct buffer_head *bh) 248 { 249 if (bh) 250 __brelse(bh); 251 } 252 253 static inline void bforget(struct buffer_head *bh) 254 { 255 if (bh) 256 __bforget(bh); 257 } 258 259 static inline struct buffer_head * 260 sb_bread(struct super_block *sb, sector_t block) 261 { 262 return __bread(sb->s_bdev, block, sb->s_blocksize); 263 } 264 265 static inline void 266 sb_breadahead(struct super_block *sb, sector_t block) 267 { 268 __breadahead(sb->s_bdev, block, sb->s_blocksize); 269 } 270 271 static inline struct buffer_head * 272 sb_getblk(struct super_block *sb, sector_t block) 273 { 274 return __getblk(sb->s_bdev, block, sb->s_blocksize); 275 } 276 277 static inline struct buffer_head * 278 sb_find_get_block(struct super_block *sb, sector_t block) 279 { 280 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 281 } 282 283 static inline void 284 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 285 { 286 set_buffer_mapped(bh); 287 bh->b_bdev = sb->s_bdev; 288 bh->b_blocknr = block; 289 bh->b_size = sb->s_blocksize; 290 } 291 292 /* 293 * Calling wait_on_buffer() for a zero-ref buffer is illegal, so we call into 294 * __wait_on_buffer() just to trip a debug check. Because debug code in inline 295 * functions is bloaty. 296 */ 297 static inline void wait_on_buffer(struct buffer_head *bh) 298 { 299 might_sleep(); 300 if (buffer_locked(bh) || atomic_read(&bh->b_count) == 0) 301 __wait_on_buffer(bh); 302 } 303 304 static inline void lock_buffer(struct buffer_head *bh) 305 { 306 might_sleep(); 307 if (test_set_buffer_locked(bh)) 308 __lock_buffer(bh); 309 } 310 311 extern int __set_page_dirty_buffers(struct page *page); 312 313 #else /* CONFIG_BLOCK */ 314 315 static inline void buffer_init(void) {} 316 static inline int try_to_free_buffers(struct page *page) { return 1; } 317 static inline int sync_blockdev(struct block_device *bdev) { return 0; } 318 static inline int inode_has_buffers(struct inode *inode) { return 0; } 319 static inline void invalidate_inode_buffers(struct inode *inode) {} 320 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 321 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 322 static inline void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers) {} 323 324 325 #endif /* CONFIG_BLOCK */ 326 #endif /* _LINUX_BUFFER_HEAD_H */ 327