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_Unwritten, /* Buffer is allocated on disk but not written */ 36 BH_Quiet, /* Buffer Error Prinks to be quiet */ 37 38 BH_PrivateStart,/* not a state bit, but the first bit available 39 * for private allocation by other entities 40 */ 41 }; 42 43 #define MAX_BUF_PER_PAGE (PAGE_CACHE_SIZE / 512) 44 45 struct page; 46 struct buffer_head; 47 struct address_space; 48 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate); 49 50 /* 51 * Historically, a buffer_head was used to map a single block 52 * within a page, and of course as the unit of I/O through the 53 * filesystem and block layers. Nowadays the basic I/O unit 54 * is the bio, and buffer_heads are used for extracting block 55 * mappings (via a get_block_t call), for tracking state within 56 * a page (via a page_mapping) and for wrapping bio submission 57 * for backward compatibility reasons (e.g. submit_bh). 58 */ 59 struct buffer_head { 60 unsigned long b_state; /* buffer state bitmap (see above) */ 61 struct buffer_head *b_this_page;/* circular list of page's buffers */ 62 struct page *b_page; /* the page this bh is mapped to */ 63 64 sector_t b_blocknr; /* start block number */ 65 size_t b_size; /* size of mapping */ 66 char *b_data; /* pointer to data within the page */ 67 68 struct block_device *b_bdev; 69 bh_end_io_t *b_end_io; /* I/O completion */ 70 void *b_private; /* reserved for b_end_io */ 71 struct list_head b_assoc_buffers; /* associated with another mapping */ 72 struct address_space *b_assoc_map; /* mapping this buffer is 73 associated with */ 74 atomic_t b_count; /* users using this buffer_head */ 75 }; 76 77 /* 78 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() 79 * and buffer_foo() functions. 80 */ 81 #define BUFFER_FNS(bit, name) \ 82 static inline void set_buffer_##name(struct buffer_head *bh) \ 83 { \ 84 set_bit(BH_##bit, &(bh)->b_state); \ 85 } \ 86 static inline void clear_buffer_##name(struct buffer_head *bh) \ 87 { \ 88 clear_bit(BH_##bit, &(bh)->b_state); \ 89 } \ 90 static inline int buffer_##name(const struct buffer_head *bh) \ 91 { \ 92 return test_bit(BH_##bit, &(bh)->b_state); \ 93 } 94 95 /* 96 * test_set_buffer_foo() and test_clear_buffer_foo() 97 */ 98 #define TAS_BUFFER_FNS(bit, name) \ 99 static inline int test_set_buffer_##name(struct buffer_head *bh) \ 100 { \ 101 return test_and_set_bit(BH_##bit, &(bh)->b_state); \ 102 } \ 103 static inline int test_clear_buffer_##name(struct buffer_head *bh) \ 104 { \ 105 return test_and_clear_bit(BH_##bit, &(bh)->b_state); \ 106 } \ 107 108 /* 109 * Emit the buffer bitops functions. Note that there are also functions 110 * of the form "mark_buffer_foo()". These are higher-level functions which 111 * do something in addition to setting a b_state bit. 112 */ 113 BUFFER_FNS(Uptodate, uptodate) 114 BUFFER_FNS(Dirty, dirty) 115 TAS_BUFFER_FNS(Dirty, dirty) 116 BUFFER_FNS(Lock, locked) 117 BUFFER_FNS(Req, req) 118 TAS_BUFFER_FNS(Req, req) 119 BUFFER_FNS(Mapped, mapped) 120 BUFFER_FNS(New, new) 121 BUFFER_FNS(Async_Read, async_read) 122 BUFFER_FNS(Async_Write, async_write) 123 BUFFER_FNS(Delay, delay) 124 BUFFER_FNS(Boundary, boundary) 125 BUFFER_FNS(Write_EIO, write_io_error) 126 BUFFER_FNS(Unwritten, unwritten) 127 128 #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) 129 #define touch_buffer(bh) mark_page_accessed(bh->b_page) 130 131 /* If we *know* page->private refers to buffer_heads */ 132 #define page_buffers(page) \ 133 ({ \ 134 BUG_ON(!PagePrivate(page)); \ 135 ((struct buffer_head *)page_private(page)); \ 136 }) 137 #define page_has_buffers(page) PagePrivate(page) 138 139 /* 140 * Declarations 141 */ 142 143 void mark_buffer_dirty(struct buffer_head *bh); 144 void init_buffer(struct buffer_head *, bh_end_io_t *, void *); 145 void set_bh_page(struct buffer_head *bh, 146 struct page *page, unsigned long offset); 147 int try_to_free_buffers(struct page *); 148 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, 149 int retry); 150 void create_empty_buffers(struct page *, unsigned long, 151 unsigned long b_state); 152 void end_buffer_read_sync(struct buffer_head *bh, int uptodate); 153 void end_buffer_write_sync(struct buffer_head *bh, int uptodate); 154 void end_buffer_async_write(struct buffer_head *bh, int uptodate); 155 156 /* Things to do with buffers at mapping->private_list */ 157 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode); 158 int inode_has_buffers(struct inode *); 159 void invalidate_inode_buffers(struct inode *); 160 int remove_inode_buffers(struct inode *inode); 161 int sync_mapping_buffers(struct address_space *mapping); 162 void unmap_underlying_metadata(struct block_device *bdev, sector_t block); 163 164 void mark_buffer_async_write(struct buffer_head *bh); 165 void __wait_on_buffer(struct buffer_head *); 166 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); 167 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, 168 unsigned size); 169 struct buffer_head *__getblk(struct block_device *bdev, sector_t block, 170 unsigned size); 171 void __brelse(struct buffer_head *); 172 void __bforget(struct buffer_head *); 173 void __breadahead(struct block_device *, sector_t block, unsigned int size); 174 struct buffer_head *__bread(struct block_device *, sector_t block, unsigned size); 175 void invalidate_bh_lrus(void); 176 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags); 177 void free_buffer_head(struct buffer_head * bh); 178 void unlock_buffer(struct buffer_head *bh); 179 void __lock_buffer(struct buffer_head *bh); 180 void ll_rw_block(int, int, struct buffer_head * bh[]); 181 int sync_dirty_buffer(struct buffer_head *bh); 182 int __sync_dirty_buffer(struct buffer_head *bh, int rw); 183 void write_dirty_buffer(struct buffer_head *bh, int rw); 184 int submit_bh(int, struct buffer_head *); 185 void write_boundary_block(struct block_device *bdev, 186 sector_t bblock, unsigned blocksize); 187 int bh_uptodate_or_lock(struct buffer_head *bh); 188 int bh_submit_read(struct buffer_head *bh); 189 190 extern int buffer_heads_over_limit; 191 192 /* 193 * Generic address_space_operations implementations for buffer_head-backed 194 * address_spaces. 195 */ 196 void block_invalidatepage(struct page *page, unsigned long offset); 197 int block_write_full_page(struct page *page, get_block_t *get_block, 198 struct writeback_control *wbc); 199 int block_write_full_page_endio(struct page *page, get_block_t *get_block, 200 struct writeback_control *wbc, bh_end_io_t *handler); 201 int block_read_full_page(struct page*, get_block_t*); 202 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, 203 unsigned long from); 204 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, 205 unsigned flags, struct page **pagep, get_block_t *get_block); 206 int __block_write_begin(struct page *page, loff_t pos, unsigned len, 207 get_block_t *get_block); 208 int block_write_end(struct file *, struct address_space *, 209 loff_t, unsigned, unsigned, 210 struct page *, void *); 211 int generic_write_end(struct file *, struct address_space *, 212 loff_t, unsigned, unsigned, 213 struct page *, void *); 214 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to); 215 int cont_write_begin(struct file *, struct address_space *, loff_t, 216 unsigned, unsigned, struct page **, void **, 217 get_block_t *, loff_t *); 218 int generic_cont_expand_simple(struct inode *inode, loff_t size); 219 int block_commit_write(struct page *page, unsigned from, unsigned to); 220 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, 221 get_block_t get_block); 222 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); 223 int block_truncate_page(struct address_space *, loff_t, get_block_t *); 224 int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned, 225 struct page **, void **, get_block_t*); 226 int nobh_write_end(struct file *, struct address_space *, 227 loff_t, unsigned, unsigned, 228 struct page *, void *); 229 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *); 230 int nobh_writepage(struct page *page, get_block_t *get_block, 231 struct writeback_control *wbc); 232 233 void buffer_init(void); 234 235 /* 236 * inline definitions 237 */ 238 239 static inline void attach_page_buffers(struct page *page, 240 struct buffer_head *head) 241 { 242 page_cache_get(page); 243 SetPagePrivate(page); 244 set_page_private(page, (unsigned long)head); 245 } 246 247 static inline void get_bh(struct buffer_head *bh) 248 { 249 atomic_inc(&bh->b_count); 250 } 251 252 static inline void put_bh(struct buffer_head *bh) 253 { 254 smp_mb__before_atomic_dec(); 255 atomic_dec(&bh->b_count); 256 } 257 258 static inline void brelse(struct buffer_head *bh) 259 { 260 if (bh) 261 __brelse(bh); 262 } 263 264 static inline void bforget(struct buffer_head *bh) 265 { 266 if (bh) 267 __bforget(bh); 268 } 269 270 static inline struct buffer_head * 271 sb_bread(struct super_block *sb, sector_t block) 272 { 273 return __bread(sb->s_bdev, block, sb->s_blocksize); 274 } 275 276 static inline void 277 sb_breadahead(struct super_block *sb, sector_t block) 278 { 279 __breadahead(sb->s_bdev, block, sb->s_blocksize); 280 } 281 282 static inline struct buffer_head * 283 sb_getblk(struct super_block *sb, sector_t block) 284 { 285 return __getblk(sb->s_bdev, block, sb->s_blocksize); 286 } 287 288 static inline struct buffer_head * 289 sb_find_get_block(struct super_block *sb, sector_t block) 290 { 291 return __find_get_block(sb->s_bdev, block, sb->s_blocksize); 292 } 293 294 static inline void 295 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block) 296 { 297 set_buffer_mapped(bh); 298 bh->b_bdev = sb->s_bdev; 299 bh->b_blocknr = block; 300 bh->b_size = sb->s_blocksize; 301 } 302 303 static inline void wait_on_buffer(struct buffer_head *bh) 304 { 305 might_sleep(); 306 if (buffer_locked(bh)) 307 __wait_on_buffer(bh); 308 } 309 310 static inline int trylock_buffer(struct buffer_head *bh) 311 { 312 return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state)); 313 } 314 315 static inline void lock_buffer(struct buffer_head *bh) 316 { 317 might_sleep(); 318 if (!trylock_buffer(bh)) 319 __lock_buffer(bh); 320 } 321 322 extern int __set_page_dirty_buffers(struct page *page); 323 324 #else /* CONFIG_BLOCK */ 325 326 static inline void buffer_init(void) {} 327 static inline int try_to_free_buffers(struct page *page) { return 1; } 328 static inline int inode_has_buffers(struct inode *inode) { return 0; } 329 static inline void invalidate_inode_buffers(struct inode *inode) {} 330 static inline int remove_inode_buffers(struct inode *inode) { return 1; } 331 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; } 332 333 #endif /* CONFIG_BLOCK */ 334 #endif /* _LINUX_BUFFER_HEAD_H */ 335