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