include/linux/buffer_head.h

   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 void block_sync_page(struct page *);
 223 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 224 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
 225 int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned,
 226                                 struct page **, void **, get_block_t*);
 227 int nobh_write_end(struct file *, struct address_space *,
 228                                 loff_t, unsigned, unsigned,
 229                                 struct page *, void *);
 230 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
 231 int nobh_writepage(struct page *page, get_block_t *get_block,
 232                         struct writeback_control *wbc);
 233
 234 void buffer_init(void);
 235
 236 /*
 237  * inline definitions
 238  */
 239
 240 static inline void attach_page_buffers(struct page *page,
 241                 struct buffer_head *head)
 242 {
 243         page_cache_get(page);
 244         SetPagePrivate(page);
 245         set_page_private(page, (unsigned long)head);
 246 }
 247
 248 static inline void get_bh(struct buffer_head *bh)
 249 {
 250         atomic_inc(&bh->b_count);
 251 }
 252
 253 static inline void put_bh(struct buffer_head *bh)
 254 {
 255         smp_mb__before_atomic_dec();
 256         atomic_dec(&bh->b_count);
 257 }
 258
 259 static inline void brelse(struct buffer_head *bh)
 260 {
 261         if (bh)
 262                 __brelse(bh);
 263 }
 264
 265 static inline void bforget(struct buffer_head *bh)
 266 {
 267         if (bh)
 268                 __bforget(bh);
 269 }
 270
 271 static inline struct buffer_head *
 272 sb_bread(struct super_block *sb, sector_t block)
 273 {
 274         return __bread(sb->s_bdev, block, sb->s_blocksize);
 275 }
 276
 277 static inline void
 278 sb_breadahead(struct super_block *sb, sector_t block)
 279 {
 280         __breadahead(sb->s_bdev, block, sb->s_blocksize);
 281 }
 282
 283 static inline struct buffer_head *
 284 sb_getblk(struct super_block *sb, sector_t block)
 285 {
 286         return __getblk(sb->s_bdev, block, sb->s_blocksize);
 287 }
 288
 289 static inline struct buffer_head *
 290 sb_find_get_block(struct super_block *sb, sector_t block)
 291 {
 292         return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
 293 }
 294
 295 static inline void
 296 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 297 {
 298         set_buffer_mapped(bh);
 299         bh->b_bdev = sb->s_bdev;
 300         bh->b_blocknr = block;
 301         bh->b_size = sb->s_blocksize;
 302 }
 303
 304 static inline void wait_on_buffer(struct buffer_head *bh)
 305 {
 306         might_sleep();
 307         if (buffer_locked(bh))
 308                 __wait_on_buffer(bh);
 309 }
 310
 311 static inline int trylock_buffer(struct buffer_head *bh)
 312 {
 313         return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
 314 }
 315
 316 static inline void lock_buffer(struct buffer_head *bh)
 317 {
 318         might_sleep();
 319         if (!trylock_buffer(bh))
 320                 __lock_buffer(bh);
 321 }
 322
 323 extern int __set_page_dirty_buffers(struct page *page);
 324
 325 #else /* CONFIG_BLOCK */
 326
 327 static inline void buffer_init(void) {}
 328 static inline int try_to_free_buffers(struct page *page) { return 1; }
 329 static inline int inode_has_buffers(struct inode *inode) { return 0; }
 330 static inline void invalidate_inode_buffers(struct inode *inode) {}
 331 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 332 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 333
 334 #endif /* CONFIG_BLOCK */
 335 #endif /* _LINUX_BUFFER_HEAD_H */