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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         BH_Unwritten,   /* Buffer is allocated on disk but not written */
  38
  39         BH_PrivateStart,/* not a state bit, but the first bit available
  40                          * for private allocation by other entities
  41                          */
  42 };
  43
  44 #define MAX_BUF_PER_PAGE (PAGE_CACHE_SIZE / 512)
  45
  46 struct page;
  47 struct buffer_head;
  48 struct address_space;
  49 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
  50
  51 /*
  52  * Historically, a buffer_head was used to map a single block
  53  * within a page, and of course as the unit of I/O through the
  54  * filesystem and block layers.  Nowadays the basic I/O unit
  55  * is the bio, and buffer_heads are used for extracting block
  56  * mappings (via a get_block_t call), for tracking state within
  57  * a page (via a page_mapping) and for wrapping bio submission
  58  * for backward compatibility reasons (e.g. submit_bh).
  59  */
  60 struct buffer_head {
  61         unsigned long b_state;          /* buffer state bitmap (see above) */
  62         struct buffer_head *b_this_page;/* circular list of page's buffers */
  63         struct page *b_page;            /* the page this bh is mapped to */
  64
  65         sector_t b_blocknr;             /* start block number */
  66         size_t b_size;                  /* size of mapping */
  67         char *b_data;                   /* pointer to data within the page */
  68
  69         struct block_device *b_bdev;
  70         bh_end_io_t *b_end_io;          /* I/O completion */
  71         void *b_private;                /* reserved for b_end_io */
  72         struct list_head b_assoc_buffers; /* associated with another mapping */
  73         struct address_space *b_assoc_map;      /* mapping this buffer is
  74                                                    associated with */
  75         atomic_t b_count;               /* users using this buffer_head */
  76 };
  77
  78 /*
  79  * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
  80  * and buffer_foo() functions.
  81  */
  82 #define BUFFER_FNS(bit, name)                                           \
  83 static inline void set_buffer_##name(struct buffer_head *bh)            \
  84 {                                                                       \
  85         set_bit(BH_##bit, &(bh)->b_state);                              \
  86 }                                                                       \
  87 static inline void clear_buffer_##name(struct buffer_head *bh)          \
  88 {                                                                       \
  89         clear_bit(BH_##bit, &(bh)->b_state);                            \
  90 }                                                                       \
  91 static inline int buffer_##name(const struct buffer_head *bh)           \
  92 {                                                                       \
  93         return test_bit(BH_##bit, &(bh)->b_state);                      \
  94 }
  95
  96 /*
  97  * test_set_buffer_foo() and test_clear_buffer_foo()
  98  */
  99 #define TAS_BUFFER_FNS(bit, name)                                       \
 100 static inline int test_set_buffer_##name(struct buffer_head *bh)        \
 101 {                                                                       \
 102         return test_and_set_bit(BH_##bit, &(bh)->b_state);              \
 103 }                                                                       \
 104 static inline int test_clear_buffer_##name(struct buffer_head *bh)      \
 105 {                                                                       \
 106         return test_and_clear_bit(BH_##bit, &(bh)->b_state);            \
 107 }                                                                       \
 108
 109 /*
 110  * Emit the buffer bitops functions.   Note that there are also functions
 111  * of the form "mark_buffer_foo()".  These are higher-level functions which
 112  * do something in addition to setting a b_state bit.
 113  */
 114 BUFFER_FNS(Uptodate, uptodate)
 115 BUFFER_FNS(Dirty, dirty)
 116 TAS_BUFFER_FNS(Dirty, dirty)
 117 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 BUFFER_FNS(Unwritten, unwritten)
 130
 131 #define bh_offset(bh)           ((unsigned long)(bh)->b_data & ~PAGE_MASK)
 132 #define touch_buffer(bh)        mark_page_accessed(bh->b_page)
 133
 134 /* If we *know* page->private refers to buffer_heads */
 135 #define page_buffers(page)                                      \
 136         ({                                                      \
 137                 BUG_ON(!PagePrivate(page));                     \
 138                 ((struct buffer_head *)page_private(page));     \
 139         })
 140 #define page_has_buffers(page)  PagePrivate(page)
 141
 142 /*
 143  * Declarations
 144  */
 145
 146 void mark_buffer_dirty(struct buffer_head *bh);
 147 void init_buffer(struct buffer_head *, bh_end_io_t *, void *);
 148 void set_bh_page(struct buffer_head *bh,
 149                 struct page *page, unsigned long offset);
 150 int try_to_free_buffers(struct page *);
 151 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 152                 int retry);
 153 void create_empty_buffers(struct page *, unsigned long,
 154                         unsigned long b_state);
 155 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
 156 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
 157
 158 /* Things to do with buffers at mapping->private_list */
 159 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
 160 int inode_has_buffers(struct inode *);
 161 void invalidate_inode_buffers(struct inode *);
 162 int remove_inode_buffers(struct inode *inode);
 163 int sync_mapping_buffers(struct address_space *mapping);
 164 void unmap_underlying_metadata(struct block_device *bdev, sector_t block);
 165
 166 void mark_buffer_async_write(struct buffer_head *bh);
 167 void invalidate_bdev(struct block_device *);
 168 int sync_blockdev(struct block_device *bdev);
 169 void __wait_on_buffer(struct buffer_head *);
 170 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
 171 int fsync_bdev(struct block_device *);
 172 struct super_block *freeze_bdev(struct block_device *);
 173 void thaw_bdev(struct block_device *, struct super_block *);
 174 int fsync_super(struct super_block *);
 175 int fsync_no_super(struct block_device *);
 176 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
 177                         unsigned size);
 178 struct buffer_head *__getblk(struct block_device *bdev, sector_t block,
 179                         unsigned size);
 180 void __brelse(struct buffer_head *);
 181 void __bforget(struct buffer_head *);
 182 void __breadahead(struct block_device *, sector_t block, unsigned int size);
 183 struct buffer_head *__bread(struct block_device *, sector_t block, unsigned size);
 184 void invalidate_bh_lrus(void);
 185 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 186 void free_buffer_head(struct buffer_head * bh);
 187 void unlock_buffer(struct buffer_head *bh);
 188 void __lock_buffer(struct buffer_head *bh);
 189 void ll_rw_block(int, int, struct buffer_head * bh[]);
 190 int sync_dirty_buffer(struct buffer_head *bh);
 191 int submit_bh(int, struct buffer_head *);
 192 void write_boundary_block(struct block_device *bdev,
 193                         sector_t bblock, unsigned blocksize);
 194 int bh_uptodate_or_lock(struct buffer_head *bh);
 195 int bh_submit_read(struct buffer_head *bh);
 196
 197 extern int buffer_heads_over_limit;
 198
 199 /*
 200  * Generic address_space_operations implementations for buffer_head-backed
 201  * address_spaces.
 202  */
 203 void block_invalidatepage(struct page *page, unsigned long offset);
 204 int block_write_full_page(struct page *page, get_block_t *get_block,
 205                                 struct writeback_control *wbc);
 206 int block_read_full_page(struct page*, get_block_t*);
 207 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
 208                                 unsigned long from);
 209 int block_write_begin(struct file *, struct address_space *,
 210                                 loff_t, unsigned, unsigned,
 211                                 struct page **, void **, get_block_t*);
 212 int block_write_end(struct file *, struct address_space *,
 213                                 loff_t, unsigned, unsigned,
 214                                 struct page *, void *);
 215 int generic_write_end(struct file *, struct address_space *,
 216                                 loff_t, unsigned, unsigned,
 217                                 struct page *, void *);
 218 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
 219 int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
 220 int cont_write_begin(struct file *, struct address_space *, loff_t,
 221                         unsigned, unsigned, struct page **, void **,
 222                         get_block_t *, loff_t *);
 223 int generic_cont_expand_simple(struct inode *inode, loff_t size);
 224 int block_commit_write(struct page *page, unsigned from, unsigned to);
 225 int block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
 226                                 get_block_t get_block);
 227 void block_sync_page(struct page *);
 228 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 229 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
 230 int file_fsync(struct file *, struct dentry *, int);
 231 int nobh_write_begin(struct file *, struct address_space *,
 232                                 loff_t, unsigned, unsigned,
 233                                 struct page **, void **, get_block_t*);
 234 int nobh_write_end(struct file *, struct address_space *,
 235                                 loff_t, unsigned, unsigned,
 236                                 struct page *, void *);
 237 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
 238 int nobh_writepage(struct page *page, get_block_t *get_block,
 239                         struct writeback_control *wbc);
 240
 241 void buffer_init(void);
 242
 243 /*
 244  * inline definitions
 245  */
 246
 247 static inline void attach_page_buffers(struct page *page,
 248                 struct buffer_head *head)
 249 {
 250         page_cache_get(page);
 251         SetPagePrivate(page);
 252         set_page_private(page, (unsigned long)head);
 253 }
 254
 255 static inline void get_bh(struct buffer_head *bh)
 256 {
 257         atomic_inc(&bh->b_count);
 258 }
 259
 260 static inline void put_bh(struct buffer_head *bh)
 261 {
 262         smp_mb__before_atomic_dec();
 263         atomic_dec(&bh->b_count);
 264 }
 265
 266 static inline void brelse(struct buffer_head *bh)
 267 {
 268         if (bh)
 269                 __brelse(bh);
 270 }
 271
 272 static inline void bforget(struct buffer_head *bh)
 273 {
 274         if (bh)
 275                 __bforget(bh);
 276 }
 277
 278 static inline struct buffer_head *
 279 sb_bread(struct super_block *sb, sector_t block)
 280 {
 281         return __bread(sb->s_bdev, block, sb->s_blocksize);
 282 }
 283
 284 static inline void
 285 sb_breadahead(struct super_block *sb, sector_t block)
 286 {
 287         __breadahead(sb->s_bdev, block, sb->s_blocksize);
 288 }
 289
 290 static inline struct buffer_head *
 291 sb_getblk(struct super_block *sb, sector_t block)
 292 {
 293         return __getblk(sb->s_bdev, block, sb->s_blocksize);
 294 }
 295
 296 static inline struct buffer_head *
 297 sb_find_get_block(struct super_block *sb, sector_t block)
 298 {
 299         return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
 300 }
 301
 302 static inline void
 303 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 304 {
 305         set_buffer_mapped(bh);
 306         bh->b_bdev = sb->s_bdev;
 307         bh->b_blocknr = block;
 308         bh->b_size = sb->s_blocksize;
 309 }
 310
 311 /*
 312  * Calling wait_on_buffer() for a zero-ref buffer is illegal, so we call into
 313  * __wait_on_buffer() just to trip a debug check.  Because debug code in inline
 314  * functions is bloaty.
 315  */
 316 static inline void wait_on_buffer(struct buffer_head *bh)
 317 {
 318         might_sleep();
 319         if (buffer_locked(bh) || atomic_read(&bh->b_count) == 0)
 320                 __wait_on_buffer(bh);
 321 }
 322
 323 static inline int trylock_buffer(struct buffer_head *bh)
 324 {
 325         return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
 326 }
 327
 328 static inline void lock_buffer(struct buffer_head *bh)
 329 {
 330         might_sleep();
 331         if (!trylock_buffer(bh))
 332                 __lock_buffer(bh);
 333 }
 334
 335 extern int __set_page_dirty_buffers(struct page *page);
 336
 337 #else /* CONFIG_BLOCK */
 338
 339 static inline void buffer_init(void) {}
 340 static inline int try_to_free_buffers(struct page *page) { return 1; }
 341 static inline int sync_blockdev(struct block_device *bdev) { return 0; }
 342 static inline int inode_has_buffers(struct inode *inode) { return 0; }
 343 static inline void invalidate_inode_buffers(struct inode *inode) {}
 344 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 345 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 346 static inline void invalidate_bdev(struct block_device *bdev) {}
 347
 348
 349 #endif /* CONFIG_BLOCK */
 350 #endif /* _LINUX_BUFFER_HEAD_H */