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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 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 */