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         BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise
  26                           * IO completion of other buffers in the page
  27                           */
  28
  29         BH_Mapped,      /* Has a disk mapping */
  30         BH_New,         /* Disk mapping was newly created by get_block */
  31         BH_Async_Read,  /* Is under end_buffer_async_read I/O */
  32         BH_Async_Write, /* Is under end_buffer_async_write I/O */
  33         BH_Delay,       /* Buffer is not yet allocated on disk */
  34         BH_Boundary,    /* Block is followed by a discontiguity */
  35         BH_Write_EIO,   /* I/O error on write */
  36         BH_Unwritten,   /* Buffer is allocated on disk but not written */
  37         BH_Quiet,       /* Buffer Error Prinks to be quiet */
  38         BH_Meta,        /* Buffer contains metadata */
  39         BH_Prio,        /* Buffer should be submitted with REQ_PRIO */
  40         BH_Defer_Completion, /* Defer AIO completion to workqueue */
  41
  42         BH_PrivateStart,/* not a state bit, but the first bit available
  43                          * for private allocation by other entities
  44                          */
  45 };
  46
  47 #define MAX_BUF_PER_PAGE (PAGE_SIZE / 512)
  48
  49 struct page;
  50 struct buffer_head;
  51 struct address_space;
  52 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
  53
  54 /*
  55  * Historically, a buffer_head was used to map a single block
  56  * within a page, and of course as the unit of I/O through the
  57  * filesystem and block layers.  Nowadays the basic I/O unit
  58  * is the bio, and buffer_heads are used for extracting block
  59  * mappings (via a get_block_t call), for tracking state within
  60  * a page (via a page_mapping) and for wrapping bio submission
  61  * for backward compatibility reasons (e.g. submit_bh).
  62  */
  63 struct buffer_head {
  64         unsigned long b_state;          /* buffer state bitmap (see above) */
  65         struct buffer_head *b_this_page;/* circular list of page's buffers */
  66         struct page *b_page;            /* the page this bh is mapped to */
  67
  68         sector_t b_blocknr;             /* start block number */
  69         size_t b_size;                  /* size of mapping */
  70         char *b_data;                   /* pointer to data within the page */
  71
  72         struct block_device *b_bdev;
  73         bh_end_io_t *b_end_io;          /* I/O completion */
  74         void *b_private;                /* reserved for b_end_io */
  75         struct list_head b_assoc_buffers; /* associated with another mapping */
  76         struct address_space *b_assoc_map;      /* mapping this buffer is
  77                                                    associated with */
  78         atomic_t b_count;               /* users using this buffer_head */
  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
 148 void buffer_check_dirty_writeback(struct page *page,
 149                                      bool *dirty, bool *writeback);
 150
 151 /*
 152  * Declarations
 153  */
 154
 155 void mark_buffer_dirty(struct buffer_head *bh);
 156 void mark_buffer_write_io_error(struct buffer_head *bh);
 157 void init_buffer(struct buffer_head *, bh_end_io_t *, void *);
 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 int try_to_free_buffers(struct page *);
 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 struct buffer_head *__bread_gfp(struct block_device *,
 194                                 sector_t block, unsigned size, gfp_t gfp);
 195 void invalidate_bh_lrus(void);
 196 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 197 void free_buffer_head(struct buffer_head * bh);
 198 void unlock_buffer(struct buffer_head *bh);
 199 void __lock_buffer(struct buffer_head *bh);
 200 void ll_rw_block(int, int, int, struct buffer_head * bh[]);
 201 int sync_dirty_buffer(struct buffer_head *bh);
 202 int __sync_dirty_buffer(struct buffer_head *bh, int op_flags);
 203 void write_dirty_buffer(struct buffer_head *bh, int op_flags);
 204 int submit_bh(int, int, struct buffer_head *);
 205 void write_boundary_block(struct block_device *bdev,
 206                         sector_t bblock, unsigned blocksize);
 207 int bh_uptodate_or_lock(struct buffer_head *bh);
 208 int bh_submit_read(struct buffer_head *bh);
 209 loff_t page_cache_seek_hole_data(struct inode *inode, loff_t offset,
 210                                  loff_t length, int whence);
 211
 212 extern int buffer_heads_over_limit;
 213
 214 /*
 215  * Generic address_space_operations implementations for buffer_head-backed
 216  * address_spaces.
 217  */
 218 void block_invalidatepage(struct page *page, unsigned int offset,
 219                           unsigned int length);
 220 int block_write_full_page(struct page *page, get_block_t *get_block,
 221                                 struct writeback_control *wbc);
 222 int __block_write_full_page(struct inode *inode, struct page *page,
 223                         get_block_t *get_block, struct writeback_control *wbc,
 224                         bh_end_io_t *handler);
 225 int block_read_full_page(struct page*, get_block_t*);
 226 int block_is_partially_uptodate(struct page *page, unsigned long from,
 227                                 unsigned long count);
 228 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
 229                 unsigned flags, 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, 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 int 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, unsigned,
 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 attach_page_buffers(struct page *page,
 277                 struct buffer_head *head)
 278 {
 279         get_page(page);
 280         SetPagePrivate(page);
 281         set_page_private(page, (unsigned long)head);
 282 }
 283
 284 static inline void get_bh(struct buffer_head *bh)
 285 {
 286         atomic_inc(&bh->b_count);
 287 }
 288
 289 static inline void put_bh(struct buffer_head *bh)
 290 {
 291         smp_mb__before_atomic();
 292         atomic_dec(&bh->b_count);
 293 }
 294
 295 static inline void brelse(struct buffer_head *bh)
 296 {
 297         if (bh)
 298                 __brelse(bh);
 299 }
 300
 301 static inline void bforget(struct buffer_head *bh)
 302 {
 303         if (bh)
 304                 __bforget(bh);
 305 }
 306
 307 static inline struct buffer_head *
 308 sb_bread(struct super_block *sb, sector_t block)
 309 {
 310         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 311 }
 312
 313 static inline struct buffer_head *
 314 sb_bread_unmovable(struct super_block *sb, sector_t block)
 315 {
 316         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
 317 }
 318
 319 static inline void
 320 sb_breadahead(struct super_block *sb, sector_t block)
 321 {
 322         __breadahead(sb->s_bdev, block, sb->s_blocksize);
 323 }
 324
 325 static inline struct buffer_head *
 326 sb_getblk(struct super_block *sb, sector_t block)
 327 {
 328         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 329 }
 330
 331
 332 static inline struct buffer_head *
 333 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
 334 {
 335         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
 336 }
 337
 338 static inline struct buffer_head *
 339 sb_find_get_block(struct super_block *sb, sector_t block)
 340 {
 341         return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
 342 }
 343
 344 static inline void
 345 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 346 {
 347         set_buffer_mapped(bh);
 348         bh->b_bdev = sb->s_bdev;
 349         bh->b_blocknr = block;
 350         bh->b_size = sb->s_blocksize;
 351 }
 352
 353 static inline void wait_on_buffer(struct buffer_head *bh)
 354 {
 355         might_sleep();
 356         if (buffer_locked(bh))
 357                 __wait_on_buffer(bh);
 358 }
 359
 360 static inline int trylock_buffer(struct buffer_head *bh)
 361 {
 362         return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
 363 }
 364
 365 static inline void lock_buffer(struct buffer_head *bh)
 366 {
 367         might_sleep();
 368         if (!trylock_buffer(bh))
 369                 __lock_buffer(bh);
 370 }
 371
 372 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
 373                                                    sector_t block,
 374                                                    unsigned size)
 375 {
 376         return __getblk_gfp(bdev, block, size, 0);
 377 }
 378
 379 static inline struct buffer_head *__getblk(struct block_device *bdev,
 380                                            sector_t block,
 381                                            unsigned size)
 382 {
 383         return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
 384 }
 385
 386 /**
 387  *  __bread() - reads a specified block and returns the bh
 388  *  @bdev: the block_device to read from
 389  *  @block: number of block
 390  *  @size: size (in bytes) to read
 391  *
 392  *  Reads a specified block, and returns buffer head that contains it.
 393  *  The page cache is allocated from movable area so that it can be migrated.
 394  *  It returns NULL if the block was unreadable.
 395  */
 396 static inline struct buffer_head *
 397 __bread(struct block_device *bdev, sector_t block, unsigned size)
 398 {
 399         return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
 400 }
 401
 402 extern int __set_page_dirty_buffers(struct page *page);
 403
 404 #else /* CONFIG_BLOCK */
 405
 406 static inline void buffer_init(void) {}
 407 static inline int try_to_free_buffers(struct page *page) { return 1; }
 408 static inline int inode_has_buffers(struct inode *inode) { return 0; }
 409 static inline void invalidate_inode_buffers(struct inode *inode) {}
 410 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 411 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 412
 413 #endif /* CONFIG_BLOCK */
 414 #endif /* _LINUX_BUFFER_HEAD_H */