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 touch_buffer(struct buffer_head *bh);
 158 void set_bh_page(struct buffer_head *bh,
 159                 struct page *page, unsigned long offset);
 160 int try_to_free_buffers(struct page *);
 161 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 162                 bool retry);
 163 void create_empty_buffers(struct page *, unsigned long,
 164                         unsigned long b_state);
 165 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
 166 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
 167 void end_buffer_async_write(struct buffer_head *bh, int uptodate);
 168
 169 /* Things to do with buffers at mapping->private_list */
 170 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
 171 int inode_has_buffers(struct inode *);
 172 void invalidate_inode_buffers(struct inode *);
 173 int remove_inode_buffers(struct inode *inode);
 174 int sync_mapping_buffers(struct address_space *mapping);
 175 void clean_bdev_aliases(struct block_device *bdev, sector_t block,
 176                         sector_t len);
 177 static inline void clean_bdev_bh_alias(struct buffer_head *bh)
 178 {
 179         clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
 180 }
 181
 182 void mark_buffer_async_write(struct buffer_head *bh);
 183 void __wait_on_buffer(struct buffer_head *);
 184 wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
 185 struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
 186                         unsigned size);
 187 struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
 188                                   unsigned size, gfp_t gfp);
 189 void __brelse(struct buffer_head *);
 190 void __bforget(struct buffer_head *);
 191 void __breadahead(struct block_device *, sector_t block, unsigned int size);
 192 struct buffer_head *__bread_gfp(struct block_device *,
 193                                 sector_t block, unsigned size, gfp_t gfp);
 194 void invalidate_bh_lrus(void);
 195 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 196 void free_buffer_head(struct buffer_head * bh);
 197 void unlock_buffer(struct buffer_head *bh);
 198 void __lock_buffer(struct buffer_head *bh);
 199 void ll_rw_block(int, int, int, struct buffer_head * bh[]);
 200 int sync_dirty_buffer(struct buffer_head *bh);
 201 int __sync_dirty_buffer(struct buffer_head *bh, int op_flags);
 202 void write_dirty_buffer(struct buffer_head *bh, int op_flags);
 203 int submit_bh(int, int, struct buffer_head *);
 204 void write_boundary_block(struct block_device *bdev,
 205                         sector_t bblock, unsigned blocksize);
 206 int bh_uptodate_or_lock(struct buffer_head *bh);
 207 int bh_submit_read(struct buffer_head *bh);
 208
 209 extern int buffer_heads_over_limit;
 210
 211 /*
 212  * Generic address_space_operations implementations for buffer_head-backed
 213  * address_spaces.
 214  */
 215 void block_invalidatepage(struct page *page, unsigned int offset,
 216                           unsigned int length);
 217 int block_write_full_page(struct page *page, get_block_t *get_block,
 218                                 struct writeback_control *wbc);
 219 int __block_write_full_page(struct inode *inode, struct page *page,
 220                         get_block_t *get_block, struct writeback_control *wbc,
 221                         bh_end_io_t *handler);
 222 int block_read_full_page(struct page*, get_block_t*);
 223 int block_is_partially_uptodate(struct page *page, unsigned long from,
 224                                 unsigned long count);
 225 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
 226                 unsigned flags, struct page **pagep, get_block_t *get_block);
 227 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
 228                 get_block_t *get_block);
 229 int block_write_end(struct file *, struct address_space *,
 230                                 loff_t, unsigned, unsigned,
 231                                 struct page *, void *);
 232 int generic_write_end(struct file *, struct address_space *,
 233                                 loff_t, unsigned, unsigned,
 234                                 struct page *, void *);
 235 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
 236 void clean_page_buffers(struct page *page);
 237 int cont_write_begin(struct file *, struct address_space *, loff_t,
 238                         unsigned, unsigned, struct page **, void **,
 239                         get_block_t *, loff_t *);
 240 int generic_cont_expand_simple(struct inode *inode, loff_t size);
 241 int block_commit_write(struct page *page, unsigned from, unsigned to);
 242 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 243                                 get_block_t get_block);
 244 /* Convert errno to return value from ->page_mkwrite() call */
 245 static inline int block_page_mkwrite_return(int err)
 246 {
 247         if (err == 0)
 248                 return VM_FAULT_LOCKED;
 249         if (err == -EFAULT || err == -EAGAIN)
 250                 return VM_FAULT_NOPAGE;
 251         if (err == -ENOMEM)
 252                 return VM_FAULT_OOM;
 253         /* -ENOSPC, -EDQUOT, -EIO ... */
 254         return VM_FAULT_SIGBUS;
 255 }
 256 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 257 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
 258 int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned,
 259                                 struct page **, void **, get_block_t*);
 260 int nobh_write_end(struct file *, struct address_space *,
 261                                 loff_t, unsigned, unsigned,
 262                                 struct page *, void *);
 263 int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
 264 int nobh_writepage(struct page *page, get_block_t *get_block,
 265                         struct writeback_control *wbc);
 266
 267 void buffer_init(void);
 268
 269 /*
 270  * inline definitions
 271  */
 272
 273 static inline void attach_page_buffers(struct page *page,
 274                 struct buffer_head *head)
 275 {
 276         get_page(page);
 277         SetPagePrivate(page);
 278         set_page_private(page, (unsigned long)head);
 279 }
 280
 281 static inline void get_bh(struct buffer_head *bh)
 282 {
 283         atomic_inc(&bh->b_count);
 284 }
 285
 286 static inline void put_bh(struct buffer_head *bh)
 287 {
 288         smp_mb__before_atomic();
 289         atomic_dec(&bh->b_count);
 290 }
 291
 292 static inline void brelse(struct buffer_head *bh)
 293 {
 294         if (bh)
 295                 __brelse(bh);
 296 }
 297
 298 static inline void bforget(struct buffer_head *bh)
 299 {
 300         if (bh)
 301                 __bforget(bh);
 302 }
 303
 304 static inline struct buffer_head *
 305 sb_bread(struct super_block *sb, sector_t block)
 306 {
 307         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 308 }
 309
 310 static inline struct buffer_head *
 311 sb_bread_unmovable(struct super_block *sb, sector_t block)
 312 {
 313         return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
 314 }
 315
 316 static inline void
 317 sb_breadahead(struct super_block *sb, sector_t block)
 318 {
 319         __breadahead(sb->s_bdev, block, sb->s_blocksize);
 320 }
 321
 322 static inline struct buffer_head *
 323 sb_getblk(struct super_block *sb, sector_t block)
 324 {
 325         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 326 }
 327
 328
 329 static inline struct buffer_head *
 330 sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
 331 {
 332         return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
 333 }
 334
 335 static inline struct buffer_head *
 336 sb_find_get_block(struct super_block *sb, sector_t block)
 337 {
 338         return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
 339 }
 340
 341 static inline void
 342 map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 343 {
 344         set_buffer_mapped(bh);
 345         bh->b_bdev = sb->s_bdev;
 346         bh->b_blocknr = block;
 347         bh->b_size = sb->s_blocksize;
 348 }
 349
 350 static inline void wait_on_buffer(struct buffer_head *bh)
 351 {
 352         might_sleep();
 353         if (buffer_locked(bh))
 354                 __wait_on_buffer(bh);
 355 }
 356
 357 static inline int trylock_buffer(struct buffer_head *bh)
 358 {
 359         return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
 360 }
 361
 362 static inline void lock_buffer(struct buffer_head *bh)
 363 {
 364         might_sleep();
 365         if (!trylock_buffer(bh))
 366                 __lock_buffer(bh);
 367 }
 368
 369 static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
 370                                                    sector_t block,
 371                                                    unsigned size)
 372 {
 373         return __getblk_gfp(bdev, block, size, 0);
 374 }
 375
 376 static inline struct buffer_head *__getblk(struct block_device *bdev,
 377                                            sector_t block,
 378                                            unsigned size)
 379 {
 380         return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
 381 }
 382
 383 /**
 384  *  __bread() - reads a specified block and returns the bh
 385  *  @bdev: the block_device to read from
 386  *  @block: number of block
 387  *  @size: size (in bytes) to read
 388  *
 389  *  Reads a specified block, and returns buffer head that contains it.
 390  *  The page cache is allocated from movable area so that it can be migrated.
 391  *  It returns NULL if the block was unreadable.
 392  */
 393 static inline struct buffer_head *
 394 __bread(struct block_device *bdev, sector_t block, unsigned size)
 395 {
 396         return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
 397 }
 398
 399 extern int __set_page_dirty_buffers(struct page *page);
 400
 401 #else /* CONFIG_BLOCK */
 402
 403 static inline void buffer_init(void) {}
 404 static inline int try_to_free_buffers(struct page *page) { return 1; }
 405 static inline int inode_has_buffers(struct inode *inode) { return 0; }
 406 static inline void invalidate_inode_buffers(struct inode *inode) {}
 407 static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 408 static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 409
 410 #endif /* CONFIG_BLOCK */
 411 #endif /* _LINUX_BUFFER_HEAD_H */