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 enum bh_state_bits { 18 BH_Uptodate, /* Contains valid data */ 19 BH_Dirty, /* Is dirty */ 20 BH_Lock, /* Is locked */ 21 BH_Req, /* Has been submitted for I/O */ 22 BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise 23 * IO completion of other buffers in the page 24 */ 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_Ordered, /* ordered write */ 34 BH_Eopnotsupp, /* operation not supported (barrier) */ 35 36 BH_PrivateStart,/* not a state bit, but the first bit available 37 * for private allocation by other entities 38 */ 39 }; 40 41 #define MAX_BUF_PER_PAGE (PAGE_CACHE_SIZE / 512) 42 43 struct page; 44 struct buffer_head; 45 struct address_space; 46 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate); 47 48 /* 49 * Historically, a buffer_head was used to map a single block 50 * within a page, and of course as the unit of I/O through the 51 * filesystem and block layers. Nowadays the basic I/O unit 52 * is the bio, and buffer_heads are used for extracting block 53 * mappings (via a get_block_t call), for tracking state within 54 * a page (via a page_mapping) and for wrapping bio submission 55 * for backward compatibility reasons (e.g. submit_bh). 56 */ 57 struct buffer_head { 58 unsigned long b_state; /* buffer state bitmap (see above) */ 59 struct buffer_head *b_this_page;/* circular list of page's buffers */ 60 struct page *b_page; /* the page this bh is mapped to */ 61 62 sector_t b_blocknr; /* start block number */ 63 size_t b_size; /* size of mapping */ 64 char *b_data; /* pointer to data within the page */ 65 66 struct block_device *b_bdev; 67 bh_end_io_t *b_end_io; /* I/O completion */ 68 void *b_private; /* reserved for b_end_io */ 69 struct list_head b_assoc_buffers; /* associated with another mapping */ 70 atomic_t b_count; /* users using this buffer_head */ 71 }; 72 73 /* 74 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() 75 * and buffer_foo() functions. 76 */ 77 #define BUFFER_FNS(bit, name) \ 78 static inline void set_buffer_##name(struct buffer_head *bh) \ 79 { \ 80 set_bit(BH_##bit, &(bh)->b_state); \ 81 } \ 82 static inline void clear_buffer_##name(struct buffer_head *bh) \ 83 { \ 84 clear_bit(BH_##bit, &(bh)->b_state); \ 85 } \ 86 static inline int buffer_##name(const struct buffer_head *bh) \ 87 { \ 88 return test_bit(BH_##bit, &(bh)->b_state); \ 89 } 90 91 /* 92 * test_set_buffer_foo() and test_clear_buffer_foo() 93 */ 94 #define TAS_BUFFER_FNS(bit, name) \ 95 static inline int test_set_buffer_##name(struct buffer_head *bh) \ 96 { \ 97 return test_and_set_bit(BH_##bit, &(bh)->b_state); \ 98 } \ 99 static inline int test_clear_buffer_##name(struct buffer_head *bh) \ 100 { \ 101 return test_and_clear_bit(BH_##bit, &(bh)->b_state); \ 102 } \ 103 104 /* 105 * Emit the buffer bitops functions. Note that there are also functions 106 * of the form "mark_buffer_foo()". These are higher-level functions which 107 * do something in addition to setting a b_state bit. 108 */ 109 BUFFER_FNS(Uptodate, uptodate) 110 BUFFER_FNS(Dirty, dirty) 111 TAS_BUFFER_FNS(Dirty, dirty) 112 BUFFER_FNS(Lock, locked) 113 TAS_BUFFER_FNS(Lock, locked) 114 BUFFER_FNS(Req, req) 115 TAS_BUFFER_FNS(Req, req) 116 BUFFER_FNS(Mapped, mapped) 117 BUFFER_FNS(New, new) 118 BUFFER_FNS(Async_Read, async_read) 119 BUFFER_FNS(Async_Write, async_write) 120 BUFFER_FNS(Delay, delay) 121 BUFFER_FNS(Boundary, boundary) 122 BUFFER_FNS(Write_EIO, write_io_error) 123 BUFFER_FNS(Ordered, ordered) 124 BUFFER_FNS(Eopnotsupp, eopnotsupp) 125 126 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) 127 #define touch_buffer(bh) mark_page_accessed(bh->b_page) 128 129 /* If we *know* page->private refers to buffer_heads */ 130 #define page_buffers(page) \ 131 ({ \ 132 BUG_ON(!PagePrivate(page)); \ 133 ((struct buffer_head *)page_private(page)); \ 134 }) 135 #define page_has_buffers(page) PagePrivate(page) 136 137 /* 138 * Declarations 139 */ 140 141 void FASTCALL(mark_buffer_dirty(struct buffer_head *bh)); 142 void init_buffer(struct buffer_head *, bh_end_io_t *, void *); 143 void set_bh_page(struct buffer_head *bh, 144 struct page *page, unsigned long offset); 145 int try_to_free_buffers(struct page *); 146 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 147 int retry); 148 void create_empty_buffers(struct page *, unsigned long, 149 unsigned long b_state); 150 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 151 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 152 153 /* Things to do with buffers at mapping->private_list */ 154 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 155 int inode_has_buffers(struct inode *); 156 void invalidate_inode_buffers(struct inode *); 157 int remove_inode_buffers(struct inode *inode); 158 int sync_mapping_buffers(struct address_space *mapping); 159 void unmap_underlying_metadata(struct block_device *bdev, sector_t block); 160 161 void mark_buffer_async_write(struct buffer_head *bh); 162 void invalidate_bdev(struct block_device *, int); 163 int sync_blockdev(struct block_device *bdev); 164 void __wait_on_buffer(struct buffer_head *); 165 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 166 int fsync_bdev(struct block_device *); 167 struct super_block *freeze_bdev(struct block_device *); 168 void thaw_bdev(struct block_device *, struct super_block *); 169 int fsync_super(struct super_block *); 170 int fsync_no_super(struct block_device *); 171 struct buffer_head *__find_get_block(struct block_device *, sector_t, int); 172 struct buffer_head * __getblk(struct block_device *, sector_t, int); 173 void __brelse(struct buffer_head *); 174 void __bforget(struct buffer_head *); 175 void __breadahead(struct block_device *, sector_t block, int size); 176 struct buffer_head *__bread(struct block_device *, sector_t block, int size); 177 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 178 void free_buffer_head(struct buffer_head * bh); 179 void FASTCALL(unlock_buffer(struct buffer_head *bh)); 180 void FASTCALL(__lock_buffer(struct buffer_head *bh)); 181 void ll_rw_block(int, int, struct buffer_head * bh[]); 182 int sync_dirty_buffer(struct buffer_head *bh); 183 int submit_bh(int, struct buffer_head *); 184 void write_boundary_block(struct block_device *bdev, 185 sector_t bblock, unsigned blocksize); 186 187 extern int buffer_heads_over_limit; 188 189 /* 190 * Generic address_space_operations implementations for buffer_head-backed 191 * address_spaces. 192 */ 193 int try_to_release_page(struct page * page, gfp_t gfp_mask); 194 void block_invalidatepage(struct page *page, unsigned long offset); 195 void do_invalidatepage(struct page *page, unsigned long offset); 196 int block_write_full_page(struct page *page, get_block_t *get_block, 197 struct writeback_control *wbc); 198 int block_read_full_page(struct page*, get_block_t*); 199 int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*); 200 int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*, 201 loff_t *); 202 int generic_cont_expand(struct inode *inode, loff_t size); 203 int generic_cont_expand_simple(struct inode *inode, loff_t size); 204 int block_commit_write(struct page *page, unsigned from, unsigned to); 205 void block_sync_page(struct page *); 206 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 207 int generic_commit_write(struct file *, struct page *, unsigned, unsigned); 208 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 209 int file_fsync(struct file *, struct dentry *, int); 210 int nobh_prepare_write(struct page*, unsigned, unsigned, get_block_t*); 211 int nobh_commit_write(struct file *, struct page *, unsigned, unsigned); 212 int nobh_truncate_page(struct address_space *, loff_t); 213 int nobh_writepage(struct page *page, get_block_t *get_block, 214 struct writeback_control *wbc); 215 216 void buffer_init(void); 217 218 /* 219 * inline definitions 220 */ 221 222 static inline void attach_page_buffers(struct page *page, 223 struct buffer_head *head) 224 { 225 page_cache_get(page); 226 SetPagePrivate(page); 227 set_page_private(page, (unsigned long)head); 228 } 229 230 static inline void get_bh(struct buffer_head *bh) 231 { 232 atomic_inc(&bh->b_count); 233 } 234 235 static inline void put_bh(struct buffer_head *bh) 236 { 237 smp_mb__before_atomic_dec(); 238 atomic_dec(&bh->b_count); 239 } 240 241 static inline void brelse(struct buffer_head *bh) 242 { 243 if (bh) 244 __brelse(bh); 245 } 246 247 static inline void bforget(struct buffer_head *bh) 248 { 249 if (bh) 250 __bforget(bh); 251 } 252 253 static inline struct buffer_head * 254 sb_bread(struct super_block *sb, sector_t block) 255 { 256 return __bread(sb->s_bdev, block, sb->s_blocksize); 257 } 258 259 static inline void 260 sb_breadahead(struct super_block *sb, sector_t block) 261 { 262 __breadahead(sb->s_bdev, block, sb->s_blocksize); 263 } 264 265 static inline struct buffer_head * 266 sb_getblk(struct super_block *sb, sector_t block) 267 { 268 return __getblk(sb->s_bdev, block, sb->s_blocksize); 269 } 270 271 static inline struct buffer_head * 272 sb_find_get_block(struct super_block *sb, sector_t block) 273 { 274 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 275 } 276 277 static inline void 278 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 279 { 280 set_buffer_mapped(bh); 281 bh->b_bdev = sb->s_bdev; 282 bh->b_blocknr = block; 283 bh->b_size = sb->s_blocksize; 284 } 285 286 /* 287 * Calling wait_on_buffer() for a zero-ref buffer is illegal, so we call into 288 * __wait_on_buffer() just to trip a debug check. Because debug code in inline 289 * functions is bloaty. 290 */ 291 static inline void wait_on_buffer(struct buffer_head *bh) 292 { 293 might_sleep(); 294 if (buffer_locked(bh) || atomic_read(&bh->b_count) == 0) 295 __wait_on_buffer(bh); 296 } 297 298 static inline void lock_buffer(struct buffer_head *bh) 299 { 300 might_sleep(); 301 if (test_set_buffer_locked(bh)) 302 __lock_buffer(bh); 303 } 304 305 #endif /* _LINUX_BUFFER_HEAD_H */ 306