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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         atomic_t b_count;               /* users using this buffer_head */
  73 };
  74
  75 /*
  76  * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
  77  * and buffer_foo() functions.
  78  */
  79 #define BUFFER_FNS(bit, name)                                           \
  80 static inline void set_buffer_##name(struct buffer_head *bh)            \
  81 {                                                                       \
  82         set_bit(BH_##bit, &(bh)->b_state);                              \
  83 }                                                                       \
  84 static inline void clear_buffer_##name(struct buffer_head *bh)          \
  85 {                                                                       \
  86         clear_bit(BH_##bit, &(bh)->b_state);                            \
  87 }                                                                       \
  88 static inline int buffer_##name(const struct buffer_head *bh)           \
  89 {                                                                       \
  90         return test_bit(BH_##bit, &(bh)->b_state);                      \
  91 }
  92
  93 /*
  94  * test_set_buffer_foo() and test_clear_buffer_foo()
  95  */
  96 #define TAS_BUFFER_FNS(bit, name)                                       \
  97 static inline int test_set_buffer_##name(struct buffer_head *bh)        \
  98 {                                                                       \
  99         return test_and_set_bit(BH_##bit, &(bh)->b_state);              \
 100 }                                                                       \
 101 static inline int test_clear_buffer_##name(struct buffer_head *bh)      \
 102 {                                                                       \
 103         return test_and_clear_bit(BH_##bit, &(bh)->b_state);            \
 104 }                                                                       \
 105
 106 /*
 107  * Emit the buffer bitops functions.   Note that there are also functions
 108  * of the form "mark_buffer_foo()".  These are higher-level functions which
 109  * do something in addition to setting a b_state bit.
 110  */
 111 BUFFER_FNS(Uptodate, uptodate)
 112 BUFFER_FNS(Dirty, dirty)
 113 TAS_BUFFER_FNS(Dirty, dirty)
 114 BUFFER_FNS(Lock, locked)
 115 TAS_BUFFER_FNS(Lock, locked)
 116 BUFFER_FNS(Req, req)
 117 TAS_BUFFER_FNS(Req, req)
 118 BUFFER_FNS(Mapped, mapped)
 119 BUFFER_FNS(New, new)
 120 BUFFER_FNS(Async_Read, async_read)
 121 BUFFER_FNS(Async_Write, async_write)
 122 BUFFER_FNS(Delay, delay)
 123 BUFFER_FNS(Boundary, boundary)
 124 BUFFER_FNS(Write_EIO, write_io_error)
 125 BUFFER_FNS(Ordered, ordered)
 126 BUFFER_FNS(Eopnotsupp, eopnotsupp)
 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 FASTCALL(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
 155 /* Things to do with buffers at mapping->private_list */
 156 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
 157 int inode_has_buffers(struct inode *);
 158 void invalidate_inode_buffers(struct inode *);
 159 int remove_inode_buffers(struct inode *inode);
 160 int sync_mapping_buffers(struct address_space *mapping);
 161 void unmap_underlying_metadata(struct block_device *bdev, sector_t block);
 162
 163 void mark_buffer_async_write(struct buffer_head *bh);
 164 void invalidate_bdev(struct block_device *, int);
 165 int sync_blockdev(struct block_device *bdev);
 166 void __wait_on_buffer(struct buffer_head *);
 167 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
 168 int fsync_bdev(struct block_device *);
 169 struct super_block *freeze_bdev(struct block_device *);
 170 void thaw_bdev(struct block_device *, struct super_block *);
 171 int fsync_super(struct super_block *);
 172 int fsync_no_super(struct block_device *);
 173 struct buffer_head *__find_get_block(struct block_device *, sector_t, int);
 174 struct buffer_head * __getblk(struct block_device *, sector_t, int);
 175 void __brelse(struct buffer_head *);
 176 void __bforget(struct buffer_head *);
 177 void __breadahead(struct block_device *, sector_t block, int size);
 178 struct buffer_head *__bread(struct block_device *, sector_t block, int size);
 179 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 180 void free_buffer_head(struct buffer_head * bh);
 181 void FASTCALL(unlock_buffer(struct buffer_head *bh));
 182 void FASTCALL(__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
 189 extern int buffer_heads_over_limit;
 190
 191 /*
 192  * Generic address_space_operations implementations for buffer_head-backed
 193  * address_spaces.
 194  */
 195 void block_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 extern int __set_page_dirty_buffers(struct page *page);
 306
 307 #else /* CONFIG_BLOCK */
 308
 309 static inline void buffer_init(void) {}
 310 static inline int try_to_free_buffers(struct page *page) { return 1; }
 311 static inline int sync_blockdev(struct block_device *bdev) { return 0; }
 312 static inline int inode_has_buffers(struct inode *inode) { return 0; }
 313 static inline void invalidate_inode_buffers(struct inode *inode) {}
 314 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 315 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 316 static inline void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers) {}
 317
 318
 319 #endif /* CONFIG_BLOCK */
 320 #endif /* _LINUX_BUFFER_HEAD_H */