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/fs.h>
  13 #include <linux/linkage.h>
  14 #include <linux/pagemap.h>
  15 #include <linux/wait.h>
  16 #include <linux/atomic.h>
  17
  18 #ifdef CONFIG_BLOCK
  19
  20 enum bh_state_bits {
  21         BH_Uptodate,    /* Contains valid data */
  22         BH_Dirty,       /* Is dirty */
  23         BH_Lock,        /* Is locked */
  24         BH_Req,         /* Has been submitted for I/O */
  25
  26         BH_Mapped,      /* Has a disk mapping */
  27         BH_New,         /* Disk mapping was newly created by get_block */
  28         BH_Async_Read,  /* Is under end_buffer_async_read I/O */
  29         BH_Async_Write, /* Is under end_buffer_async_write I/O */
  30         BH_Delay,       /* Buffer is not yet allocated on disk */
  31         BH_Boundary,    /* Block is followed by a discontiguity */
  32         BH_Write_EIO,   /* I/O error on write */
  33         BH_Unwritten,   /* Buffer is allocated on disk but not written */
  34         BH_Quiet,       /* Buffer Error Prinks to be quiet */
  35         BH_Meta,        /* Buffer contains metadata */
  36         BH_Prio,        /* Buffer should be submitted with REQ_PRIO */
  37         BH_Defer_Completion, /* Defer AIO completion to workqueue */
  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_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         spinlock_t b_uptodate_lock;     /* Used by the first bh in a page, to
  77                                          * serialise IO completion of other
  78                                          * buffers in the page */
  79 };
  80
  81 /*
  82  * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
  83  * and buffer_foo() functions.
  84  * To avoid reset buffer flags that are already set, because that causes
  85  * a costly cache line transition, check the flag first.
  86  */
  87 #define BUFFER_FNS(bit, name)                                           \
  88 static __always_inline void set_buffer_##name(struct buffer_head *bh)   \
  89 {                                                                       \
  90         if (!test_bit(BH_##bit, &(bh)->b_state))                        \
  91                 set_bit(BH_##bit, &(bh)->b_state);                      \
  92 }                                                                       \
  93 static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
  94 {                                                                       \
  95         clear_bit(BH_##bit, &(bh)->b_state);                            \
  96 }                                                                       \
  97 static __always_inline int buffer_##name(const struct buffer_head *bh)  \
  98 {                                                                       \
  99         return test_bit(BH_##bit, &(bh)->b_state);                      \
 100 }
 101
 102 /*
 103  * test_set_buffer_foo() and test_clear_buffer_foo()
 104  */
 105 #define TAS_BUFFER_FNS(bit, name)                                       \
 106 static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
 107 {                                                                       \
 108         return test_and_set_bit(BH_##bit, &(bh)->b_state);              \
 109 }                                                                       \
 110 static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \
 111 {                                                                       \
 112         return test_and_clear_bit(BH_##bit, &(bh)->b_state);            \
 113 }                                                                       \
 114
 115 /*
 116  * Emit the buffer bitops functions.   Note that there are also functions
 117  * of the form "mark_buffer_foo()".  These are higher-level functions which
 118  * do something in addition to setting a b_state bit.
 119  */
 120 BUFFER_FNS(Uptodate, uptodate)
 121 BUFFER_FNS(Dirty, dirty)
 122 TAS_BUFFER_FNS(Dirty, dirty)
 123 BUFFER_FNS(Lock, locked)
 124 BUFFER_FNS(Req, req)
 125 TAS_BUFFER_FNS(Req, req)
 126 BUFFER_FNS(Mapped, mapped)
 127 BUFFER_FNS(New, new)
 128 BUFFER_FNS(Async_Read, async_read)
 129 BUFFER_FNS(Async_Write, async_write)
 130 BUFFER_FNS(Delay, delay)
 131 BUFFER_FNS(Boundary, boundary)
 132 BUFFER_FNS(Write_EIO, write_io_error)
 133 BUFFER_FNS(Unwritten, unwritten)
 134 BUFFER_FNS(Meta, meta)
 135 BUFFER_FNS(Prio, prio)
 136 BUFFER_FNS(Defer_Completion, defer_completion)
 137
 138 #define bh_offset(bh)           ((unsigned long)(bh)->b_data & ~PAGE_MASK)
 139
 140 /* If we *know* page->private refers to buffer_heads */
 141 #define page_buffers(page)                                      \
 142         ({                                                      \
 143                 BUG_ON(!PagePrivate(page));                     \
 144                 ((struct buffer_head *)page_private(page));     \
 145         })
 146 #define page_has_buffers(page)  PagePrivate(page)
 147 #define folio_buffers(folio)            folio_get_private(folio)
 148
 149 void buffer_check_dirty_writeback(struct folio *folio,
 150                                      bool *dirty, bool *writeback);
 151
 152 /*
 153  * Declarations
 154  */
 155
 156 void mark_buffer_dirty(struct buffer_head *bh);
 157 void mark_buffer_write_io_error(struct buffer_head *bh);
 158 void touch_buffer(struct buffer_head *bh);
 159 void set_bh_page(struct buffer_head *bh,
 160                 struct page *page, unsigned long offset);
 161 bool try_to_free_buffers(struct folio *);
 162 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 163                 bool retry);
 164 void create_empty_buffers(struct page *, unsigned long,
 165                         unsigned long b_state);
 166 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
 167 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
 168 void end_buffer_async_write(struct buffer_head *bh, int uptodate);
 169
 170 /* Things to do with buffers at mapping->private_list */
 171 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
 172 int inode_has_buffers(struct inode *);
 173 void invalidate_inode_buffers(struct inode *);
 174 int remove_inode_buffers(struct inode *inode);
 175 int sync_mapping_buffers(struct address_space *mapping);
 176 void clean_bdev_aliases(struct block_device *bdev, sector_t block,
 177                         sector_t len);
 178 static inline void clean_bdev_bh_alias(struct buffer_head *bh)
 179 {
 180         clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
 181 }
 182
 183 void mark_buffer_async_write(struct buffer_head *bh);
 184 void __wait_on_buffer(struct buffer_head *);
 185 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
 186 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
 187                         unsigned size);
 188 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
 189                                   unsigned size, gfp_t gfp);
 190 void __brelse(struct buffer_head *);
 191 void __bforget(struct buffer_head *);
 192 void __breadahead(struct block_device *, sector_t block, unsigned int size);
 193 void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size,
 194                   gfp_t gfp);
 195 struct buffer_head *__bread_gfp(struct block_device *,
 196                                 sector_t block, unsigned size, gfp_t gfp);
 197 void invalidate_bh_lrus(void);
 198 void invalidate_bh_lrus_cpu(void);
 199 bool has_bh_in_lru(int cpu, void *dummy);
 200 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 201 void free_buffer_head(struct buffer_head * bh);
 202 void unlock_buffer(struct buffer_head *bh);
 203 void __lock_buffer(struct buffer_head *bh);
 204 void ll_rw_block(int, int, int, struct buffer_head * bh[]);
 205 int sync_dirty_buffer(struct buffer_head *bh);
 206 int __sync_dirty_buffer(struct buffer_head *bh, int op_flags);
 207 void write_dirty_buffer(struct buffer_head *bh, int op_flags);
 208 int submit_bh(int, int, struct buffer_head *);
 209 void write_boundary_block(struct block_device *bdev,
 210                         sector_t bblock, unsigned blocksize);
 211 int bh_uptodate_or_lock(struct buffer_head *bh);
 212 int bh_submit_read(struct buffer_head *bh);
 213
 214 extern int buffer_heads_over_limit;
 215
 216 /*
 217  * Generic address_space_operations implementations for buffer_head-backed
 218  * address_spaces.
 219  */
 220 void block_invalidate_folio(struct folio *folio, size_t offset, size_t length);
 221 int block_write_full_page(struct page *page, get_block_t *get_block,
 222                                 struct writeback_control *wbc);
 223 int __block_write_full_page(struct inode *inode, struct page *page,
 224                         get_block_t *get_block, struct writeback_control *wbc,
 225                         bh_end_io_t *handler);
 226 int block_read_full_folio(struct folio *, get_block_t *);
 227 bool block_is_partially_uptodate(struct folio *, size_t from, size_t count);
 228 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
 229                 struct page **pagep, get_block_t *get_block);
 230 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
 231                 get_block_t *get_block);
 232 int block_write_end(struct file *, struct address_space *,
 233                                 loff_t, unsigned, unsigned,
 234                                 struct page *, void *);
 235 int generic_write_end(struct file *, struct address_space *,
 236                                 loff_t, unsigned, unsigned,
 237                                 struct page *, void *);
 238 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
 239 void clean_page_buffers(struct page *page);
 240 int cont_write_begin(struct file *, struct address_space *, loff_t,
 241                         unsigned, struct page **, void **,
 242                         get_block_t *, loff_t *);
 243 int generic_cont_expand_simple(struct inode *inode, loff_t size);
 244 int block_commit_write(struct page *page, unsigned from, unsigned to);
 245 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 246                                 get_block_t get_block);
 247 /* Convert errno to return value from ->page_mkwrite() call */
 248 static inline vm_fault_t block_page_mkwrite_return(int err)
 249 {
 250         if (err == 0)
 251                 return VM_FAULT_LOCKED;
 252         if (err == -EFAULT || err == -EAGAIN)
 253                 return VM_FAULT_NOPAGE;
 254         if (err == -ENOMEM)
 255                 return VM_FAULT_OOM;
 256         /* -ENOSPC, -EDQUOT, -EIO ... */
 257         return VM_FAULT_SIGBUS;
 258 }
 259 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 260 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
 261 int nobh_write_begin(struct address_space *, loff_t, unsigned len,
 262                                 struct page **, void **, get_block_t*);
 263 int nobh_write_end(struct file *, struct address_space *,
 264                                 loff_t, unsigned, unsigned,
 265                                 struct page *, void *);
 266 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
 267 int nobh_writepage(struct page *page, get_block_t *get_block,
 268                         struct writeback_control *wbc);
 269
 270 void buffer_init(void);
 271
 272 /*
 273  * inline definitions
 274  */
 275
 276 static inline void get_bh(struct buffer_head *bh)
 277 {
 278         atomic_inc(&bh->b_count);
 279 }
 280
 281 static inline void put_bh(struct buffer_head *bh)
 282 {
 283         smp_mb__before_atomic();
 284         atomic_dec(&bh->b_count);
 285 }
 286
 287 static inline void brelse(struct buffer_head *bh)
 288 {
 289         if (bh)
 290                 __brelse(bh);
 291 }
 292
 293 static inline void bforget(struct buffer_head *bh)
 294 {
 295         if (bh)
 296                 __bforget(bh);
 297 }
 298
 299 static inline struct buffer_head *
 300 sb_bread(struct super_block *sb, sector_t block)
 301 {
 302         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 303 }
 304
 305 static inline struct buffer_head *
 306 sb_bread_unmovable(struct super_block *sb, sector_t block)
 307 {
 308         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
 309 }
 310
 311 static inline void
 312 sb_breadahead(struct super_block *sb, sector_t block)
 313 {
 314         __breadahead(sb->s_bdev, block, sb->s_blocksize);
 315 }
 316
 317 static inline void
 318 sb_breadahead_unmovable(struct super_block *sb, sector_t block)
 319 {
 320         __breadahead_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
 321 }
 322
 323 static inline struct buffer_head *
 324 sb_getblk(struct super_block *sb, sector_t block)
 325 {
 326         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 327 }
 328
 329
 330 static inline struct buffer_head *
 331 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
 332 {
 333         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
 334 }
 335
 336 static inline struct buffer_head *
 337 sb_find_get_block(struct super_block *sb, sector_t block)
 338 {
 339         return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
 340 }
 341
 342 static inline void
 343 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 344 {
 345         set_buffer_mapped(bh);
 346         bh->b_bdev = sb->s_bdev;
 347         bh->b_blocknr = block;
 348         bh->b_size = sb->s_blocksize;
 349 }
 350
 351 static inline void wait_on_buffer(struct buffer_head *bh)
 352 {
 353         might_sleep();
 354         if (buffer_locked(bh))
 355                 __wait_on_buffer(bh);
 356 }
 357
 358 static inline int trylock_buffer(struct buffer_head *bh)
 359 {
 360         return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
 361 }
 362
 363 static inline void lock_buffer(struct buffer_head *bh)
 364 {
 365         might_sleep();
 366         if (!trylock_buffer(bh))
 367                 __lock_buffer(bh);
 368 }
 369
 370 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
 371                                                    sector_t block,
 372                                                    unsigned size)
 373 {
 374         return __getblk_gfp(bdev, block, size, 0);
 375 }
 376
 377 static inline struct buffer_head *__getblk(struct block_device *bdev,
 378                                            sector_t block,
 379                                            unsigned size)
 380 {
 381         return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
 382 }
 383
 384 /**
 385  *  __bread() - reads a specified block and returns the bh
 386  *  @bdev: the block_device to read from
 387  *  @block: number of block
 388  *  @size: size (in bytes) to read
 389  *
 390  *  Reads a specified block, and returns buffer head that contains it.
 391  *  The page cache is allocated from movable area so that it can be migrated.
 392  *  It returns NULL if the block was unreadable.
 393  */
 394 static inline struct buffer_head *
 395 __bread(struct block_device *bdev, sector_t block, unsigned size)
 396 {
 397         return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
 398 }
 399
 400 bool block_dirty_folio(struct address_space *mapping, struct folio *folio);
 401
 402 #else /* CONFIG_BLOCK */
 403
 404 static inline void buffer_init(void) {}
 405 static inline bool try_to_free_buffers(struct folio *folio) { return true; }
 406 static inline int inode_has_buffers(struct inode *inode) { return 0; }
 407 static inline void invalidate_inode_buffers(struct inode *inode) {}
 408 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 409 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 410 static inline void invalidate_bh_lrus_cpu(void) {}
 411 static inline bool has_bh_in_lru(int cpu, void *dummy) { return false; }
 412 #define buffer_heads_over_limit 0
 413
 414 #endif /* CONFIG_BLOCK */
 415 #endif /* _LINUX_BUFFER_HEAD_H */