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   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
  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 TAS_BUFFER_FNS(Lock, locked)
 118 BUFFER_FNS(Req, req)
 119 TAS_BUFFER_FNS(Req, req)
 120 BUFFER_FNS(Mapped, mapped)
 121 BUFFER_FNS(New, new)
 122 BUFFER_FNS(Async_Read, async_read)
 123 BUFFER_FNS(Async_Write, async_write)
 124 BUFFER_FNS(Delay, delay)
 125 BUFFER_FNS(Boundary, boundary)
 126 BUFFER_FNS(Write_EIO, write_io_error)
 127 BUFFER_FNS(Ordered, ordered)
 128 BUFFER_FNS(Eopnotsupp, eopnotsupp)
 129
 130 #define bh_offset(bh)           ((unsigned long)(bh)->b_data & ~PAGE_MASK)
 131 #define touch_buffer(bh)        mark_page_accessed(bh->b_page)
 132
 133 /* If we *know* page->private refers to buffer_heads */
 134 #define page_buffers(page)                                      \
 135         ({                                                      \
 136                 BUG_ON(!PagePrivate(page));                     \
 137                 ((struct buffer_head *)page_private(page));     \
 138         })
 139 #define page_has_buffers(page)  PagePrivate(page)
 140
 141 /*
 142  * Declarations
 143  */
 144
 145 void FASTCALL(mark_buffer_dirty(struct buffer_head *bh));
 146 void init_buffer(struct buffer_head *, bh_end_io_t *, void *);
 147 void set_bh_page(struct buffer_head *bh,
 148                 struct page *page, unsigned long offset);
 149 int try_to_free_buffers(struct page *);
 150 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 151                 int retry);
 152 void create_empty_buffers(struct page *, unsigned long,
 153                         unsigned long b_state);
 154 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
 155 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
 156
 157 /* Things to do with buffers at mapping->private_list */
 158 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
 159 int inode_has_buffers(struct inode *);
 160 void invalidate_inode_buffers(struct inode *);
 161 int remove_inode_buffers(struct inode *inode);
 162 int sync_mapping_buffers(struct address_space *mapping);
 163 void unmap_underlying_metadata(struct block_device *bdev, sector_t block);
 164
 165 void mark_buffer_async_write(struct buffer_head *bh);
 166 void invalidate_bdev(struct block_device *, int);
 167 int sync_blockdev(struct block_device *bdev);
 168 void __wait_on_buffer(struct buffer_head *);
 169 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
 170 int fsync_bdev(struct block_device *);
 171 struct super_block *freeze_bdev(struct block_device *);
 172 void thaw_bdev(struct block_device *, struct super_block *);
 173 int fsync_super(struct super_block *);
 174 int fsync_no_super(struct block_device *);
 175 struct buffer_head *__find_get_block(struct block_device *, sector_t, int);
 176 struct buffer_head * __getblk(struct block_device *, sector_t, int);
 177 void __brelse(struct buffer_head *);
 178 void __bforget(struct buffer_head *);
 179 void __breadahead(struct block_device *, sector_t block, int size);
 180 struct buffer_head *__bread(struct block_device *, sector_t block, int size);
 181 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 182 void free_buffer_head(struct buffer_head * bh);
 183 void FASTCALL(unlock_buffer(struct buffer_head *bh));
 184 void FASTCALL(__lock_buffer(struct buffer_head *bh));
 185 void ll_rw_block(int, int, struct buffer_head * bh[]);
 186 int sync_dirty_buffer(struct buffer_head *bh);
 187 int submit_bh(int, struct buffer_head *);
 188 void write_boundary_block(struct block_device *bdev,
 189                         sector_t bblock, unsigned blocksize);
 190
 191 extern int buffer_heads_over_limit;
 192
 193 /*
 194  * Generic address_space_operations implementations for buffer_head-backed
 195  * address_spaces.
 196  */
 197 void block_invalidatepage(struct page *page, unsigned long offset);
 198 int block_write_full_page(struct page *page, get_block_t *get_block,
 199                                 struct writeback_control *wbc);
 200 int block_read_full_page(struct page*, get_block_t*);
 201 int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
 202 int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*,
 203                                 loff_t *);
 204 int generic_cont_expand(struct inode *inode, loff_t size);
 205 int generic_cont_expand_simple(struct inode *inode, loff_t size);
 206 int block_commit_write(struct page *page, unsigned from, unsigned to);
 207 void block_sync_page(struct page *);
 208 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 209 int generic_commit_write(struct file *, struct page *, unsigned, unsigned);
 210 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
 211 int file_fsync(struct file *, struct dentry *, int);
 212 int nobh_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
 213 int nobh_commit_write(struct file *, struct page *, unsigned, unsigned);
 214 int nobh_truncate_page(struct address_space *, loff_t);
 215 int nobh_writepage(struct page *page, get_block_t *get_block,
 216                         struct writeback_control *wbc);
 217
 218 void buffer_init(void);
 219
 220 /*
 221  * inline definitions
 222  */
 223
 224 static inline void attach_page_buffers(struct page *page,
 225                 struct buffer_head *head)
 226 {
 227         page_cache_get(page);
 228         SetPagePrivate(page);
 229         set_page_private(page, (unsigned long)head);
 230 }
 231
 232 static inline void get_bh(struct buffer_head *bh)
 233 {
 234         atomic_inc(&bh->b_count);
 235 }
 236
 237 static inline void put_bh(struct buffer_head *bh)
 238 {
 239         smp_mb__before_atomic_dec();
 240         atomic_dec(&bh->b_count);
 241 }
 242
 243 static inline void brelse(struct buffer_head *bh)
 244 {
 245         if (bh)
 246                 __brelse(bh);
 247 }
 248
 249 static inline void bforget(struct buffer_head *bh)
 250 {
 251         if (bh)
 252                 __bforget(bh);
 253 }
 254
 255 static inline struct buffer_head *
 256 sb_bread(struct super_block *sb, sector_t block)
 257 {
 258         return __bread(sb->s_bdev, block, sb->s_blocksize);
 259 }
 260
 261 static inline void
 262 sb_breadahead(struct super_block *sb, sector_t block)
 263 {
 264         __breadahead(sb->s_bdev, block, sb->s_blocksize);
 265 }
 266
 267 static inline struct buffer_head *
 268 sb_getblk(struct super_block *sb, sector_t block)
 269 {
 270         return __getblk(sb->s_bdev, block, sb->s_blocksize);
 271 }
 272
 273 static inline struct buffer_head *
 274 sb_find_get_block(struct super_block *sb, sector_t block)
 275 {
 276         return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
 277 }
 278
 279 static inline void
 280 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 281 {
 282         set_buffer_mapped(bh);
 283         bh->b_bdev = sb->s_bdev;
 284         bh->b_blocknr = block;
 285         bh->b_size = sb->s_blocksize;
 286 }
 287
 288 /*
 289  * Calling wait_on_buffer() for a zero-ref buffer is illegal, so we call into
 290  * __wait_on_buffer() just to trip a debug check.  Because debug code in inline
 291  * functions is bloaty.
 292  */
 293 static inline void wait_on_buffer(struct buffer_head *bh)
 294 {
 295         might_sleep();
 296         if (buffer_locked(bh) || atomic_read(&bh->b_count) == 0)
 297                 __wait_on_buffer(bh);
 298 }
 299
 300 static inline void lock_buffer(struct buffer_head *bh)
 301 {
 302         might_sleep();
 303         if (test_set_buffer_locked(bh))
 304                 __lock_buffer(bh);
 305 }
 306
 307 extern int __set_page_dirty_buffers(struct page *page);
 308
 309 #else /* CONFIG_BLOCK */
 310
 311 static inline void buffer_init(void) {}
 312 static inline int try_to_free_buffers(struct page *page) { return 1; }
 313 static inline int sync_blockdev(struct block_device *bdev) { return 0; }
 314 static inline int inode_has_buffers(struct inode *inode) { return 0; }
 315 static inline void invalidate_inode_buffers(struct inode *inode) {}
 316 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 317 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 318 static inline void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers) {}
 319
 320
 321 #endif /* CONFIG_BLOCK */
 322 #endif /* _LINUX_BUFFER_HEAD_H */