include/linux/buffer_head.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * include/linux/buffer_head.h
   4  *
   5  * Everything to do with buffer_heads.
   6  */
   7
   8 #ifndef _LINUX_BUFFER_HEAD_H
   9 #define _LINUX_BUFFER_HEAD_H
  10
  11 #include <linux/types.h>
  12 #include <linux/blk_types.h>
  13 #include <linux/fs.h>
  14 #include <linux/linkage.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/wait.h>
  17 #include <linux/atomic.h>
  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
  25         BH_Mapped,      /* Has a disk mapping */
  26         BH_New,         /* Disk mapping was newly created by get_block */
  27         BH_Async_Read,  /* Is under end_buffer_async_read I/O */
  28         BH_Async_Write, /* Is under end_buffer_async_write I/O */
  29         BH_Delay,       /* Buffer is not yet allocated on disk */
  30         BH_Boundary,    /* Block is followed by a discontiguity */
  31         BH_Write_EIO,   /* I/O error on write */
  32         BH_Unwritten,   /* Buffer is allocated on disk but not written */
  33         BH_Quiet,       /* Buffer Error Prinks to be quiet */
  34         BH_Meta,        /* Buffer contains metadata */
  35         BH_Prio,        /* Buffer should be submitted with REQ_PRIO */
  36         BH_Defer_Completion, /* Defer AIO completion to workqueue */
  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_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         union {
  63                 struct page *b_page;    /* the page this bh is mapped to */
  64                 struct folio *b_folio;  /* the folio this bh is mapped to */
  65         };
  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         spinlock_t b_uptodate_lock;     /* Used by the first bh in a page, to
  79                                          * serialise IO completion of other
  80                                          * buffers in the page */
  81 };
  82
  83 /*
  84  * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
  85  * and buffer_foo() functions.
  86  * To avoid reset buffer flags that are already set, because that causes
  87  * a costly cache line transition, check the flag first.
  88  */
  89 #define BUFFER_FNS(bit, name)                                           \
  90 static __always_inline void set_buffer_##name(struct buffer_head *bh)   \
  91 {                                                                       \
  92         if (!test_bit(BH_##bit, &(bh)->b_state))                        \
  93                 set_bit(BH_##bit, &(bh)->b_state);                      \
  94 }                                                                       \
  95 static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
  96 {                                                                       \
  97         clear_bit(BH_##bit, &(bh)->b_state);                            \
  98 }                                                                       \
  99 static __always_inline int buffer_##name(const struct buffer_head *bh)  \
 100 {                                                                       \
 101         return test_bit(BH_##bit, &(bh)->b_state);                      \
 102 }
 103
 104 /*
 105  * test_set_buffer_foo() and test_clear_buffer_foo()
 106  */
 107 #define TAS_BUFFER_FNS(bit, name)                                       \
 108 static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
 109 {                                                                       \
 110         return test_and_set_bit(BH_##bit, &(bh)->b_state);              \
 111 }                                                                       \
 112 static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \
 113 {                                                                       \
 114         return test_and_clear_bit(BH_##bit, &(bh)->b_state);            \
 115 }                                                                       \
 116
 117 /*
 118  * Emit the buffer bitops functions.   Note that there are also functions
 119  * of the form "mark_buffer_foo()".  These are higher-level functions which
 120  * do something in addition to setting a b_state bit.
 121  */
 122 BUFFER_FNS(Dirty, dirty)
 123 TAS_BUFFER_FNS(Dirty, dirty)
 124 BUFFER_FNS(Lock, locked)
 125 BUFFER_FNS(Req, req)
 126 TAS_BUFFER_FNS(Req, req)
 127 BUFFER_FNS(Mapped, mapped)
 128 BUFFER_FNS(New, new)
 129 BUFFER_FNS(Async_Read, async_read)
 130 BUFFER_FNS(Async_Write, async_write)
 131 BUFFER_FNS(Delay, delay)
 132 BUFFER_FNS(Boundary, boundary)
 133 BUFFER_FNS(Write_EIO, write_io_error)
 134 BUFFER_FNS(Unwritten, unwritten)
 135 BUFFER_FNS(Meta, meta)
 136 BUFFER_FNS(Prio, prio)
 137 BUFFER_FNS(Defer_Completion, defer_completion)
 138
 139 static __always_inline void set_buffer_uptodate(struct buffer_head *bh)
 140 {
 141         /*
 142          * If somebody else already set this uptodate, they will
 143          * have done the memory barrier, and a reader will thus
 144          * see *some* valid buffer state.
 145          *
 146          * Any other serialization (with IO errors or whatever that
 147          * might clear the bit) has to come from other state (eg BH_Lock).
 148          */
 149         if (test_bit(BH_Uptodate, &bh->b_state))
 150                 return;
 151
 152         /*
 153          * make it consistent with folio_mark_uptodate
 154          * pairs with smp_load_acquire in buffer_uptodate
 155          */
 156         smp_mb__before_atomic();
 157         set_bit(BH_Uptodate, &bh->b_state);
 158 }
 159
 160 static __always_inline void clear_buffer_uptodate(struct buffer_head *bh)
 161 {
 162         clear_bit(BH_Uptodate, &bh->b_state);
 163 }
 164
 165 static __always_inline int buffer_uptodate(const struct buffer_head *bh)
 166 {
 167         /*
 168          * make it consistent with folio_test_uptodate
 169          * pairs with smp_mb__before_atomic in set_buffer_uptodate
 170          */
 171         return test_bit_acquire(BH_Uptodate, &bh->b_state);
 172 }
 173
 174 static inline unsigned long bh_offset(const struct buffer_head *bh)
 175 {
 176         return (unsigned long)(bh)->b_data & (page_size(bh->b_page) - 1);
 177 }
 178
 179 /* If we *know* page->private refers to buffer_heads */
 180 #define page_buffers(page)                                      \
 181         ({                                                      \
 182                 BUG_ON(!PagePrivate(page));                     \
 183                 ((struct buffer_head *)page_private(page));     \
 184         })
 185 #define page_has_buffers(page)  PagePrivate(page)
 186 #define folio_buffers(folio)            folio_get_private(folio)
 187
 188 void buffer_check_dirty_writeback(struct folio *folio,
 189                                      bool *dirty, bool *writeback);
 190
 191 /*
 192  * Declarations
 193  */
 194
 195 void mark_buffer_dirty(struct buffer_head *bh);
 196 void mark_buffer_write_io_error(struct buffer_head *bh);
 197 void touch_buffer(struct buffer_head *bh);
 198 void folio_set_bh(struct buffer_head *bh, struct folio *folio,
 199                   unsigned long offset);
 200 struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size,
 201                                         gfp_t gfp);
 202 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 203                 bool retry);
 204 struct buffer_head *create_empty_buffers(struct folio *folio,
 205                 unsigned long blocksize, unsigned long b_state);
 206 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
 207 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
 208
 209 /* Things to do with buffers at mapping->private_list */
 210 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
 211 int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end,
 212                                   bool datasync);
 213 int generic_buffers_fsync(struct file *file, loff_t start, loff_t end,
 214                           bool datasync);
 215 void clean_bdev_aliases(struct block_device *bdev, sector_t block,
 216                         sector_t len);
 217 static inline void clean_bdev_bh_alias(struct buffer_head *bh)
 218 {
 219         clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
 220 }
 221
 222 void mark_buffer_async_write(struct buffer_head *bh);
 223 void __wait_on_buffer(struct buffer_head *);
 224 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
 225 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
 226                         unsigned size);
 227 struct buffer_head *bdev_getblk(struct block_device *bdev, sector_t block,
 228                 unsigned size, gfp_t gfp);
 229 void __brelse(struct buffer_head *);
 230 void __bforget(struct buffer_head *);
 231 void __breadahead(struct block_device *, sector_t block, unsigned int size);
 232 struct buffer_head *__bread_gfp(struct block_device *,
 233                                 sector_t block, unsigned size, gfp_t gfp);
 234 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 235 void free_buffer_head(struct buffer_head * bh);
 236 void unlock_buffer(struct buffer_head *bh);
 237 void __lock_buffer(struct buffer_head *bh);
 238 int sync_dirty_buffer(struct buffer_head *bh);
 239 int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags);
 240 void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags);
 241 void submit_bh(blk_opf_t, struct buffer_head *);
 242 void write_boundary_block(struct block_device *bdev,
 243                         sector_t bblock, unsigned blocksize);
 244 int bh_uptodate_or_lock(struct buffer_head *bh);
 245 int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait);
 246 void __bh_read_batch(int nr, struct buffer_head *bhs[],
 247                      blk_opf_t op_flags, bool force_lock);
 248
 249 /*
 250  * Generic address_space_operations implementations for buffer_head-backed
 251  * address_spaces.
 252  */
 253 void block_invalidate_folio(struct folio *folio, size_t offset, size_t length);
 254 int block_write_full_folio(struct folio *folio, struct writeback_control *wbc,
 255                 void *get_block);
 256 int __block_write_full_folio(struct inode *inode, struct folio *folio,
 257                 get_block_t *get_block, struct writeback_control *wbc);
 258 int block_read_full_folio(struct folio *, get_block_t *);
 259 bool block_is_partially_uptodate(struct folio *, size_t from, size_t count);
 260 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
 261                 struct page **pagep, get_block_t *get_block);
 262 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
 263                 get_block_t *get_block);
 264 int block_write_end(struct file *, struct address_space *,
 265                                 loff_t, unsigned, unsigned,
 266                                 struct page *, void *);
 267 int generic_write_end(struct file *, struct address_space *,
 268                                 loff_t, unsigned, unsigned,
 269                                 struct page *, void *);
 270 void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to);
 271 int cont_write_begin(struct file *, struct address_space *, loff_t,
 272                         unsigned, struct page **, void **,
 273                         get_block_t *, loff_t *);
 274 int generic_cont_expand_simple(struct inode *inode, loff_t size);
 275 void block_commit_write(struct page *page, unsigned int from, unsigned int to);
 276 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 277                                 get_block_t get_block);
 278 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 279 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
 280
 281 #ifdef CONFIG_MIGRATION
 282 extern int buffer_migrate_folio(struct address_space *,
 283                 struct folio *dst, struct folio *src, enum migrate_mode);
 284 extern int buffer_migrate_folio_norefs(struct address_space *,
 285                 struct folio *dst, struct folio *src, enum migrate_mode);
 286 #else
 287 #define buffer_migrate_folio NULL
 288 #define buffer_migrate_folio_norefs NULL
 289 #endif
 290
 291 /*
 292  * inline definitions
 293  */
 294
 295 static inline void get_bh(struct buffer_head *bh)
 296 {
 297         atomic_inc(&bh->b_count);
 298 }
 299
 300 static inline void put_bh(struct buffer_head *bh)
 301 {
 302         smp_mb__before_atomic();
 303         atomic_dec(&bh->b_count);
 304 }
 305
 306 static inline void brelse(struct buffer_head *bh)
 307 {
 308         if (bh)
 309                 __brelse(bh);
 310 }
 311
 312 static inline void bforget(struct buffer_head *bh)
 313 {
 314         if (bh)
 315                 __bforget(bh);
 316 }
 317
 318 static inline struct buffer_head *
 319 sb_bread(struct super_block *sb, sector_t block)
 320 {
 321         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 322 }
 323
 324 static inline struct buffer_head *
 325 sb_bread_unmovable(struct super_block *sb, sector_t block)
 326 {
 327         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
 328 }
 329
 330 static inline void
 331 sb_breadahead(struct super_block *sb, sector_t block)
 332 {
 333         __breadahead(sb->s_bdev, block, sb->s_blocksize);
 334 }
 335
 336 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
 337                 sector_t block, unsigned size)
 338 {
 339         gfp_t gfp;
 340
 341         gfp = mapping_gfp_constraint(bdev->bd_inode->i_mapping, ~__GFP_FS);
 342         gfp |= __GFP_NOFAIL;
 343
 344         return bdev_getblk(bdev, block, size, gfp);
 345 }
 346
 347 static inline struct buffer_head *__getblk(struct block_device *bdev,
 348                 sector_t block, unsigned size)
 349 {
 350         gfp_t gfp;
 351
 352         gfp = mapping_gfp_constraint(bdev->bd_inode->i_mapping, ~__GFP_FS);
 353         gfp |= __GFP_MOVABLE | __GFP_NOFAIL;
 354
 355         return bdev_getblk(bdev, block, size, gfp);
 356 }
 357
 358 static inline struct buffer_head *sb_getblk(struct super_block *sb,
 359                 sector_t block)
 360 {
 361         return __getblk(sb->s_bdev, block, sb->s_blocksize);
 362 }
 363
 364 static inline struct buffer_head *sb_getblk_gfp(struct super_block *sb,
 365                 sector_t block, gfp_t gfp)
 366 {
 367         return bdev_getblk(sb->s_bdev, block, sb->s_blocksize, gfp);
 368 }
 369
 370 static inline struct buffer_head *
 371 sb_find_get_block(struct super_block *sb, sector_t block)
 372 {
 373         return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
 374 }
 375
 376 static inline void
 377 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 378 {
 379         set_buffer_mapped(bh);
 380         bh->b_bdev = sb->s_bdev;
 381         bh->b_blocknr = block;
 382         bh->b_size = sb->s_blocksize;
 383 }
 384
 385 static inline void wait_on_buffer(struct buffer_head *bh)
 386 {
 387         might_sleep();
 388         if (buffer_locked(bh))
 389                 __wait_on_buffer(bh);
 390 }
 391
 392 static inline int trylock_buffer(struct buffer_head *bh)
 393 {
 394         return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
 395 }
 396
 397 static inline void lock_buffer(struct buffer_head *bh)
 398 {
 399         might_sleep();
 400         if (!trylock_buffer(bh))
 401                 __lock_buffer(bh);
 402 }
 403
 404 static inline void bh_readahead(struct buffer_head *bh, blk_opf_t op_flags)
 405 {
 406         if (!buffer_uptodate(bh) && trylock_buffer(bh)) {
 407                 if (!buffer_uptodate(bh))
 408                         __bh_read(bh, op_flags, false);
 409                 else
 410                         unlock_buffer(bh);
 411         }
 412 }
 413
 414 static inline void bh_read_nowait(struct buffer_head *bh, blk_opf_t op_flags)
 415 {
 416         if (!bh_uptodate_or_lock(bh))
 417                 __bh_read(bh, op_flags, false);
 418 }
 419
 420 /* Returns 1 if buffer uptodated, 0 on success, and -EIO on error. */
 421 static inline int bh_read(struct buffer_head *bh, blk_opf_t op_flags)
 422 {
 423         if (bh_uptodate_or_lock(bh))
 424                 return 1;
 425         return __bh_read(bh, op_flags, true);
 426 }
 427
 428 static inline void bh_read_batch(int nr, struct buffer_head *bhs[])
 429 {
 430         __bh_read_batch(nr, bhs, 0, true);
 431 }
 432
 433 static inline void bh_readahead_batch(int nr, struct buffer_head *bhs[],
 434                                       blk_opf_t op_flags)
 435 {
 436         __bh_read_batch(nr, bhs, op_flags, false);
 437 }
 438
 439 /**
 440  *  __bread() - reads a specified block and returns the bh
 441  *  @bdev: the block_device to read from
 442  *  @block: number of block
 443  *  @size: size (in bytes) to read
 444  *
 445  *  Reads a specified block, and returns buffer head that contains it.
 446  *  The page cache is allocated from movable area so that it can be migrated.
 447  *  It returns NULL if the block was unreadable.
 448  */
 449 static inline struct buffer_head *
 450 __bread(struct block_device *bdev, sector_t block, unsigned size)
 451 {
 452         return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
 453 }
 454
 455 /**
 456  * get_nth_bh - Get a reference on the n'th buffer after this one.
 457  * @bh: The buffer to start counting from.
 458  * @count: How many buffers to skip.
 459  *
 460  * This is primarily useful for finding the nth buffer in a folio; in
 461  * that case you pass the head buffer and the byte offset in the folio
 462  * divided by the block size.  It can be used for other purposes, but
 463  * it will wrap at the end of the folio rather than returning NULL or
 464  * proceeding to the next folio for you.
 465  *
 466  * Return: The requested buffer with an elevated refcount.
 467  */
 468 static inline __must_check
 469 struct buffer_head *get_nth_bh(struct buffer_head *bh, unsigned int count)
 470 {
 471         while (count--)
 472                 bh = bh->b_this_page;
 473         get_bh(bh);
 474         return bh;
 475 }
 476
 477 bool block_dirty_folio(struct address_space *mapping, struct folio *folio);
 478
 479 #ifdef CONFIG_BUFFER_HEAD
 480
 481 void buffer_init(void);
 482 bool try_to_free_buffers(struct folio *folio);
 483 int inode_has_buffers(struct inode *inode);
 484 void invalidate_inode_buffers(struct inode *inode);
 485 int remove_inode_buffers(struct inode *inode);
 486 int sync_mapping_buffers(struct address_space *mapping);
 487 void invalidate_bh_lrus(void);
 488 void invalidate_bh_lrus_cpu(void);
 489 bool has_bh_in_lru(int cpu, void *dummy);
 490 extern int buffer_heads_over_limit;
 491
 492 #else /* CONFIG_BUFFER_HEAD */
 493
 494 static inline void buffer_init(void) {}
 495 static inline bool try_to_free_buffers(struct folio *folio) { return true; }
 496 static inline int inode_has_buffers(struct inode *inode) { return 0; }
 497 static inline void invalidate_inode_buffers(struct inode *inode) {}
 498 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 499 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 500 static inline void invalidate_bh_lrus(void) {}
 501 static inline void invalidate_bh_lrus_cpu(void) {}
 502 static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; }
 503 #define buffer_heads_over_limit 0
 504
 505 #endif /* CONFIG_BUFFER_HEAD */
 506 #endif /* _LINUX_BUFFER_HEAD_H */