include/linux/buffer_head.h

   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 <linux/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_Unwritten,   /* Buffer is allocated on disk but not written */
  36         BH_Quiet,       /* Buffer Error Prinks to be quiet */
  37         BH_Meta,        /* Buffer contains metadata */
  38         BH_Prio,        /* Buffer should be submitted with REQ_PRIO */
  39         BH_Defer_Completion, /* Defer AIO completion to workqueue */
  40
  41         BH_PrivateStart,/* not a state bit, but the first bit available
  42                          * for private allocation by other entities
  43                          */
  44 };
  45
  46 #define MAX_BUF_PER_PAGE (PAGE_SIZE / 512)
  47
  48 struct page;
  49 struct buffer_head;
  50 struct address_space;
  51 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
  52
  53 /*
  54  * Historically, a buffer_head was used to map a single block
  55  * within a page, and of course as the unit of I/O through the
  56  * filesystem and block layers.  Nowadays the basic I/O unit
  57  * is the bio, and buffer_heads are used for extracting block
  58  * mappings (via a get_block_t call), for tracking state within
  59  * a page (via a page_mapping) and for wrapping bio submission
  60  * for backward compatibility reasons (e.g. submit_bh).
  61  */
  62 struct buffer_head {
  63         unsigned long b_state;          /* buffer state bitmap (see above) */
  64         struct buffer_head *b_this_page;/* circular list of page's buffers */
  65         struct page *b_page;            /* the page this bh is mapped to */
  66
  67         sector_t b_blocknr;             /* start block number */
  68         size_t b_size;                  /* size of mapping */
  69         char *b_data;                   /* pointer to data within the page */
  70
  71         struct block_device *b_bdev;
  72         bh_end_io_t *b_end_io;          /* I/O completion */
  73         void *b_private;                /* reserved for b_end_io */
  74         struct list_head b_assoc_buffers; /* associated with another mapping */
  75         struct address_space *b_assoc_map;      /* mapping this buffer is
  76                                                    associated with */
  77         atomic_t b_count;               /* users using this buffer_head */
  78 };
  79
  80 /*
  81  * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
  82  * and buffer_foo() functions.
  83  */
  84 #define BUFFER_FNS(bit, name)                                           \
  85 static __always_inline void set_buffer_##name(struct buffer_head *bh)   \
  86 {                                                                       \
  87         set_bit(BH_##bit, &(bh)->b_state);                              \
  88 }                                                                       \
  89 static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
  90 {                                                                       \
  91         clear_bit(BH_##bit, &(bh)->b_state);                            \
  92 }                                                                       \
  93 static __always_inline int buffer_##name(const struct buffer_head *bh)  \
  94 {                                                                       \
  95         return test_bit(BH_##bit, &(bh)->b_state);                      \
  96 }
  97
  98 /*
  99  * test_set_buffer_foo() and test_clear_buffer_foo()
 100  */
 101 #define TAS_BUFFER_FNS(bit, name)                                       \
 102 static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
 103 {                                                                       \
 104         return test_and_set_bit(BH_##bit, &(bh)->b_state);              \
 105 }                                                                       \
 106 static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \
 107 {                                                                       \
 108         return test_and_clear_bit(BH_##bit, &(bh)->b_state);            \
 109 }                                                                       \
 110
 111 /*
 112  * Emit the buffer bitops functions.   Note that there are also functions
 113  * of the form "mark_buffer_foo()".  These are higher-level functions which
 114  * do something in addition to setting a b_state bit.
 115  */
 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(Unwritten, unwritten)
 129 BUFFER_FNS(Meta, meta)
 130 BUFFER_FNS(Prio, prio)
 131 BUFFER_FNS(Defer_Completion, defer_completion)
 132
 133 static __always_inline void set_buffer_uptodate(struct buffer_head *bh)
 134 {
 135         /*
 136          * If somebody else already set this uptodate, they will
 137          * have done the memory barrier, and a reader will thus
 138          * see *some* valid buffer state.
 139          *
 140          * Any other serialization (with IO errors or whatever that
 141          * might clear the bit) has to come from other state (eg BH_Lock).
 142          */
 143         if (test_bit(BH_Uptodate, &bh->b_state))
 144                 return;
 145
 146         /*
 147          * make it consistent with folio_mark_uptodate
 148          * pairs with smp_load_acquire in buffer_uptodate
 149          */
 150         smp_mb__before_atomic();
 151         set_bit(BH_Uptodate, &bh->b_state);
 152 }
 153
 154 static __always_inline void clear_buffer_uptodate(struct buffer_head *bh)
 155 {
 156         clear_bit(BH_Uptodate, &bh->b_state);
 157 }
 158
 159 static __always_inline int buffer_uptodate(const struct buffer_head *bh)
 160 {
 161         /*
 162          * make it consistent with folio_test_uptodate
 163          * pairs with smp_mb__before_atomic in set_buffer_uptodate
 164          */
 165         return (smp_load_acquire(&bh->b_state) & (1UL << BH_Uptodate)) != 0;
 166 }
 167
 168 #define bh_offset(bh)           ((unsigned long)(bh)->b_data & ~PAGE_MASK)
 169
 170 /* If we *know* page->private refers to buffer_heads */
 171 #define page_buffers(page)                                      \
 172         ({                                                      \
 173                 BUG_ON(!PagePrivate(page));                     \
 174                 ((struct buffer_head *)page_private(page));     \
 175         })
 176 #define page_has_buffers(page)  PagePrivate(page)
 177
 178 void buffer_check_dirty_writeback(struct page *page,
 179                                      bool *dirty, bool *writeback);
 180
 181 /*
 182  * Declarations
 183  */
 184
 185 void mark_buffer_dirty(struct buffer_head *bh);
 186 void init_buffer(struct buffer_head *, bh_end_io_t *, void *);
 187 void touch_buffer(struct buffer_head *bh);
 188 void set_bh_page(struct buffer_head *bh,
 189                 struct page *page, unsigned long offset);
 190 int try_to_free_buffers(struct page *);
 191 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 192                 int retry);
 193 void create_empty_buffers(struct page *, unsigned long,
 194                         unsigned long b_state);
 195 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
 196 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
 197 void end_buffer_async_write(struct buffer_head *bh, int uptodate);
 198
 199 /* Things to do with buffers at mapping->private_list */
 200 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
 201 int inode_has_buffers(struct inode *);
 202 void invalidate_inode_buffers(struct inode *);
 203 int remove_inode_buffers(struct inode *inode);
 204 int sync_mapping_buffers(struct address_space *mapping);
 205 void unmap_underlying_metadata(struct block_device *bdev, sector_t block);
 206
 207 void mark_buffer_async_write(struct buffer_head *bh);
 208 void __wait_on_buffer(struct buffer_head *);
 209 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
 210 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
 211                         unsigned size);
 212 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
 213                                   unsigned size, gfp_t gfp);
 214 void __brelse(struct buffer_head *);
 215 void __bforget(struct buffer_head *);
 216 void __breadahead(struct block_device *, sector_t block, unsigned int size);
 217 struct buffer_head *__bread_gfp(struct block_device *,
 218                                 sector_t block, unsigned size, gfp_t gfp);
 219 void invalidate_bh_lrus(void);
 220 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 221 void free_buffer_head(struct buffer_head * bh);
 222 void unlock_buffer(struct buffer_head *bh);
 223 void __lock_buffer(struct buffer_head *bh);
 224 void ll_rw_block(int, int, int, struct buffer_head * bh[]);
 225 int sync_dirty_buffer(struct buffer_head *bh);
 226 int __sync_dirty_buffer(struct buffer_head *bh, int op_flags);
 227 void write_dirty_buffer(struct buffer_head *bh, int op_flags);
 228 int _submit_bh(int op, int op_flags, struct buffer_head *bh,
 229                unsigned long bio_flags);
 230 int submit_bh(int, int, struct buffer_head *);
 231 void write_boundary_block(struct block_device *bdev,
 232                         sector_t bblock, unsigned blocksize);
 233 int bh_uptodate_or_lock(struct buffer_head *bh);
 234 int bh_submit_read(struct buffer_head *bh);
 235
 236 extern int buffer_heads_over_limit;
 237
 238 /*
 239  * Generic address_space_operations implementations for buffer_head-backed
 240  * address_spaces.
 241  */
 242 void block_invalidatepage(struct page *page, unsigned int offset,
 243                           unsigned int length);
 244 int block_write_full_page(struct page *page, get_block_t *get_block,
 245                                 struct writeback_control *wbc);
 246 int __block_write_full_page(struct inode *inode, struct page *page,
 247                         get_block_t *get_block, struct writeback_control *wbc,
 248                         bh_end_io_t *handler);
 249 int block_read_full_page(struct page*, get_block_t*);
 250 int block_is_partially_uptodate(struct page *page, unsigned long from,
 251                                 unsigned long count);
 252 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
 253                 unsigned flags, struct page **pagep, get_block_t *get_block);
 254 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
 255                 get_block_t *get_block);
 256 int block_write_end(struct file *, struct address_space *,
 257                                 loff_t, unsigned, unsigned,
 258                                 struct page *, void *);
 259 int generic_write_end(struct file *, struct address_space *,
 260                                 loff_t, unsigned, unsigned,
 261                                 struct page *, void *);
 262 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
 263 void clean_page_buffers(struct page *page);
 264 int cont_write_begin(struct file *, struct address_space *, loff_t,
 265                         unsigned, unsigned, struct page **, void **,
 266                         get_block_t *, loff_t *);
 267 int generic_cont_expand_simple(struct inode *inode, loff_t size);
 268 int block_commit_write(struct page *page, unsigned from, unsigned to);
 269 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 270                                 get_block_t get_block);
 271 /* Convert errno to return value from ->page_mkwrite() call */
 272 static inline int block_page_mkwrite_return(int err)
 273 {
 274         if (err == 0)
 275                 return VM_FAULT_LOCKED;
 276         if (err == -EFAULT || err == -EAGAIN)
 277                 return VM_FAULT_NOPAGE;
 278         if (err == -ENOMEM)
 279                 return VM_FAULT_OOM;
 280         /* -ENOSPC, -EDQUOT, -EIO ... */
 281         return VM_FAULT_SIGBUS;
 282 }
 283 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 284 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
 285 int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned,
 286                                 struct page **, void **, get_block_t*);
 287 int nobh_write_end(struct file *, struct address_space *,
 288                                 loff_t, unsigned, unsigned,
 289                                 struct page *, void *);
 290 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
 291 int nobh_writepage(struct page *page, get_block_t *get_block,
 292                         struct writeback_control *wbc);
 293
 294 void buffer_init(void);
 295
 296 /*
 297  * inline definitions
 298  */
 299
 300 static inline void attach_page_buffers(struct page *page,
 301                 struct buffer_head *head)
 302 {
 303         get_page(page);
 304         SetPagePrivate(page);
 305         set_page_private(page, (unsigned long)head);
 306 }
 307
 308 static inline void get_bh(struct buffer_head *bh)
 309 {
 310         atomic_inc(&bh->b_count);
 311 }
 312
 313 static inline void put_bh(struct buffer_head *bh)
 314 {
 315         smp_mb__before_atomic();
 316         atomic_dec(&bh->b_count);
 317 }
 318
 319 static inline void brelse(struct buffer_head *bh)
 320 {
 321         if (bh)
 322                 __brelse(bh);
 323 }
 324
 325 static inline void bforget(struct buffer_head *bh)
 326 {
 327         if (bh)
 328                 __bforget(bh);
 329 }
 330
 331 static inline struct buffer_head *
 332 sb_bread(struct super_block *sb, sector_t block)
 333 {
 334         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 335 }
 336
 337 static inline struct buffer_head *
 338 sb_bread_unmovable(struct super_block *sb, sector_t block)
 339 {
 340         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
 341 }
 342
 343 static inline void
 344 sb_breadahead(struct super_block *sb, sector_t block)
 345 {
 346         __breadahead(sb->s_bdev, block, sb->s_blocksize);
 347 }
 348
 349 static inline struct buffer_head *
 350 sb_getblk(struct super_block *sb, sector_t block)
 351 {
 352         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 353 }
 354
 355
 356 static inline struct buffer_head *
 357 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
 358 {
 359         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
 360 }
 361
 362 static inline struct buffer_head *
 363 sb_find_get_block(struct super_block *sb, sector_t block)
 364 {
 365         return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
 366 }
 367
 368 static inline void
 369 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 370 {
 371         set_buffer_mapped(bh);
 372         bh->b_bdev = sb->s_bdev;
 373         bh->b_blocknr = block;
 374         bh->b_size = sb->s_blocksize;
 375 }
 376
 377 static inline void wait_on_buffer(struct buffer_head *bh)
 378 {
 379         might_sleep();
 380         if (buffer_locked(bh))
 381                 __wait_on_buffer(bh);
 382 }
 383
 384 static inline int trylock_buffer(struct buffer_head *bh)
 385 {
 386         return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
 387 }
 388
 389 static inline void lock_buffer(struct buffer_head *bh)
 390 {
 391         might_sleep();
 392         if (!trylock_buffer(bh))
 393                 __lock_buffer(bh);
 394 }
 395
 396 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
 397                                                    sector_t block,
 398                                                    unsigned size)
 399 {
 400         return __getblk_gfp(bdev, block, size, 0);
 401 }
 402
 403 static inline struct buffer_head *__getblk(struct block_device *bdev,
 404                                            sector_t block,
 405                                            unsigned size)
 406 {
 407         return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
 408 }
 409
 410 /**
 411  *  __bread() - reads a specified block and returns the bh
 412  *  @bdev: the block_device to read from
 413  *  @block: number of block
 414  *  @size: size (in bytes) to read
 415  *
 416  *  Reads a specified block, and returns buffer head that contains it.
 417  *  The page cache is allocated from movable area so that it can be migrated.
 418  *  It returns NULL if the block was unreadable.
 419  */
 420 static inline struct buffer_head *
 421 __bread(struct block_device *bdev, sector_t block, unsigned size)
 422 {
 423         return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
 424 }
 425
 426 extern int __set_page_dirty_buffers(struct page *page);
 427
 428 #else /* CONFIG_BLOCK */
 429
 430 static inline void buffer_init(void) {}
 431 static inline int try_to_free_buffers(struct page *page) { return 1; }
 432 static inline int inode_has_buffers(struct inode *inode) { return 0; }
 433 static inline void invalidate_inode_buffers(struct inode *inode) {}
 434 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 435 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 436
 437 #endif /* CONFIG_BLOCK */
 438 #endif /* _LINUX_BUFFER_HEAD_H */