linux/include/linux/buffer_head.h
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   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
  20enum 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
  46struct page;
  47struct buffer_head;
  48struct address_space;
  49typedef 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 */
  60struct 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)                                           \
  88static __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}                                                                       \
  93static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
  94{                                                                       \
  95        clear_bit(BH_##bit, &(bh)->b_state);                            \
  96}                                                                       \
  97static __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)                                       \
 106static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
 107{                                                                       \
 108        return test_and_set_bit(BH_##bit, &(bh)->b_state);              \
 109}                                                                       \
 110static __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 */
 120BUFFER_FNS(Uptodate, uptodate)
 121BUFFER_FNS(Dirty, dirty)
 122TAS_BUFFER_FNS(Dirty, dirty)
 123BUFFER_FNS(Lock, locked)
 124BUFFER_FNS(Req, req)
 125TAS_BUFFER_FNS(Req, req)
 126BUFFER_FNS(Mapped, mapped)
 127BUFFER_FNS(New, new)
 128BUFFER_FNS(Async_Read, async_read)
 129BUFFER_FNS(Async_Write, async_write)
 130BUFFER_FNS(Delay, delay)
 131BUFFER_FNS(Boundary, boundary)
 132BUFFER_FNS(Write_EIO, write_io_error)
 133BUFFER_FNS(Unwritten, unwritten)
 134BUFFER_FNS(Meta, meta)
 135BUFFER_FNS(Prio, prio)
 136BUFFER_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
 148void buffer_check_dirty_writeback(struct page *page,
 149                                     bool *dirty, bool *writeback);
 150
 151/*
 152 * Declarations
 153 */
 154
 155void mark_buffer_dirty(struct buffer_head *bh);
 156void mark_buffer_write_io_error(struct buffer_head *bh);
 157void touch_buffer(struct buffer_head *bh);
 158void set_bh_page(struct buffer_head *bh,
 159                struct page *page, unsigned long offset);
 160int try_to_free_buffers(struct page *);
 161struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 162                bool retry);
 163void create_empty_buffers(struct page *, unsigned long,
 164                        unsigned long b_state);
 165void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
 166void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
 167void end_buffer_async_write(struct buffer_head *bh, int uptodate);
 168
 169/* Things to do with buffers at mapping->private_list */
 170void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
 171int inode_has_buffers(struct inode *);
 172void invalidate_inode_buffers(struct inode *);
 173int remove_inode_buffers(struct inode *inode);
 174int sync_mapping_buffers(struct address_space *mapping);
 175void clean_bdev_aliases(struct block_device *bdev, sector_t block,
 176                        sector_t len);
 177static inline void clean_bdev_bh_alias(struct buffer_head *bh)
 178{
 179        clean_bdev_aliases(bh->b_bdev, bh->b_blocknr, 1);
 180}
 181
 182void mark_buffer_async_write(struct buffer_head *bh);
 183void __wait_on_buffer(struct buffer_head *);
 184wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
 185struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
 186                        unsigned size);
 187struct buffer_head *__getblk_gfp(struct block_device *bdev, sector_t block,
 188                                  unsigned size, gfp_t gfp);
 189void __brelse(struct buffer_head *);
 190void __bforget(struct buffer_head *);
 191void __breadahead(struct block_device *, sector_t block, unsigned int size);
 192void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size,
 193                  gfp_t gfp);
 194struct buffer_head *__bread_gfp(struct block_device *,
 195                                sector_t block, unsigned size, gfp_t gfp);
 196void invalidate_bh_lrus(void);
 197void invalidate_bh_lrus_cpu(int cpu);
 198bool has_bh_in_lru(int cpu, void *dummy);
 199struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
 200void free_buffer_head(struct buffer_head * bh);
 201void unlock_buffer(struct buffer_head *bh);
 202void __lock_buffer(struct buffer_head *bh);
 203void ll_rw_block(int, int, int, struct buffer_head * bh[]);
 204int sync_dirty_buffer(struct buffer_head *bh);
 205int __sync_dirty_buffer(struct buffer_head *bh, int op_flags);
 206void write_dirty_buffer(struct buffer_head *bh, int op_flags);
 207int submit_bh(int, int, struct buffer_head *);
 208void write_boundary_block(struct block_device *bdev,
 209                        sector_t bblock, unsigned blocksize);
 210int bh_uptodate_or_lock(struct buffer_head *bh);
 211int bh_submit_read(struct buffer_head *bh);
 212
 213extern int buffer_heads_over_limit;
 214
 215/*
 216 * Generic address_space_operations implementations for buffer_head-backed
 217 * address_spaces.
 218 */
 219void block_invalidatepage(struct page *page, unsigned int offset,
 220                          unsigned int length);
 221int block_write_full_page(struct page *page, get_block_t *get_block,
 222                                struct writeback_control *wbc);
 223int __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);
 226int block_read_full_page(struct page*, get_block_t*);
 227int block_is_partially_uptodate(struct page *page, unsigned long from,
 228                                unsigned long count);
 229int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
 230                unsigned flags, struct page **pagep, get_block_t *get_block);
 231int __block_write_begin(struct page *page, loff_t pos, unsigned len,
 232                get_block_t *get_block);
 233int block_write_end(struct file *, struct address_space *,
 234                                loff_t, unsigned, unsigned,
 235                                struct page *, void *);
 236int generic_write_end(struct file *, struct address_space *,
 237                                loff_t, unsigned, unsigned,
 238                                struct page *, void *);
 239void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
 240void clean_page_buffers(struct page *page);
 241int cont_write_begin(struct file *, struct address_space *, loff_t,
 242                        unsigned, unsigned, struct page **, void **,
 243                        get_block_t *, loff_t *);
 244int generic_cont_expand_simple(struct inode *inode, loff_t size);
 245int block_commit_write(struct page *page, unsigned from, unsigned to);
 246int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 247                                get_block_t get_block);
 248/* Convert errno to return value from ->page_mkwrite() call */
 249static inline vm_fault_t block_page_mkwrite_return(int err)
 250{
 251        if (err == 0)
 252                return VM_FAULT_LOCKED;
 253        if (err == -EFAULT || err == -EAGAIN)
 254                return VM_FAULT_NOPAGE;
 255        if (err == -ENOMEM)
 256                return VM_FAULT_OOM;
 257        /* -ENOSPC, -EDQUOT, -EIO ... */
 258        return VM_FAULT_SIGBUS;
 259}
 260sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 261int block_truncate_page(struct address_space *, loff_t, get_block_t *);
 262int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned,
 263                                struct page **, void **, get_block_t*);
 264int nobh_write_end(struct file *, struct address_space *,
 265                                loff_t, unsigned, unsigned,
 266                                struct page *, void *);
 267int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
 268int nobh_writepage(struct page *page, get_block_t *get_block,
 269                        struct writeback_control *wbc);
 270
 271void buffer_init(void);
 272
 273/*
 274 * inline definitions
 275 */
 276
 277static inline void get_bh(struct buffer_head *bh)
 278{
 279        atomic_inc(&bh->b_count);
 280}
 281
 282static inline void put_bh(struct buffer_head *bh)
 283{
 284        smp_mb__before_atomic();
 285        atomic_dec(&bh->b_count);
 286}
 287
 288static inline void brelse(struct buffer_head *bh)
 289{
 290        if (bh)
 291                __brelse(bh);
 292}
 293
 294static inline void bforget(struct buffer_head *bh)
 295{
 296        if (bh)
 297                __bforget(bh);
 298}
 299
 300static inline struct buffer_head *
 301sb_bread(struct super_block *sb, sector_t block)
 302{
 303        return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 304}
 305
 306static inline struct buffer_head *
 307sb_bread_unmovable(struct super_block *sb, sector_t block)
 308{
 309        return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
 310}
 311
 312static inline void
 313sb_breadahead(struct super_block *sb, sector_t block)
 314{
 315        __breadahead(sb->s_bdev, block, sb->s_blocksize);
 316}
 317
 318static inline void
 319sb_breadahead_unmovable(struct super_block *sb, sector_t block)
 320{
 321        __breadahead_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
 322}
 323
 324static inline struct buffer_head *
 325sb_getblk(struct super_block *sb, sector_t block)
 326{
 327        return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
 328}
 329
 330
 331static inline struct buffer_head *
 332sb_getblk_gfp(struct super_block *sb, sector_t block, gfp_t gfp)
 333{
 334        return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, gfp);
 335}
 336
 337static inline struct buffer_head *
 338sb_find_get_block(struct super_block *sb, sector_t block)
 339{
 340        return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
 341}
 342
 343static inline void
 344map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 345{
 346        set_buffer_mapped(bh);
 347        bh->b_bdev = sb->s_bdev;
 348        bh->b_blocknr = block;
 349        bh->b_size = sb->s_blocksize;
 350}
 351
 352static inline void wait_on_buffer(struct buffer_head *bh)
 353{
 354        might_sleep();
 355        if (buffer_locked(bh))
 356                __wait_on_buffer(bh);
 357}
 358
 359static inline int trylock_buffer(struct buffer_head *bh)
 360{
 361        return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
 362}
 363
 364static inline void lock_buffer(struct buffer_head *bh)
 365{
 366        might_sleep();
 367        if (!trylock_buffer(bh))
 368                __lock_buffer(bh);
 369}
 370
 371static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
 372                                                   sector_t block,
 373                                                   unsigned size)
 374{
 375        return __getblk_gfp(bdev, block, size, 0);
 376}
 377
 378static inline struct buffer_head *__getblk(struct block_device *bdev,
 379                                           sector_t block,
 380                                           unsigned size)
 381{
 382        return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
 383}
 384
 385/**
 386 *  __bread() - reads a specified block and returns the bh
 387 *  @bdev: the block_device to read from
 388 *  @block: number of block
 389 *  @size: size (in bytes) to read
 390 *
 391 *  Reads a specified block, and returns buffer head that contains it.
 392 *  The page cache is allocated from movable area so that it can be migrated.
 393 *  It returns NULL if the block was unreadable.
 394 */
 395static inline struct buffer_head *
 396__bread(struct block_device *bdev, sector_t block, unsigned size)
 397{
 398        return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
 399}
 400
 401extern int __set_page_dirty_buffers(struct page *page);
 402
 403#else /* CONFIG_BLOCK */
 404
 405static inline void buffer_init(void) {}
 406static inline int try_to_free_buffers(struct page *page) { return 1; }
 407static inline int inode_has_buffers(struct inode *inode) { return 0; }
 408static inline void invalidate_inode_buffers(struct inode *inode) {}
 409static inline int remove_inode_buffers(struct inode *inode) { return 1; }
 410static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
 411static inline void invalidate_bh_lrus_cpu(int cpu) {}
 412static inline bool has_bh_in_lru(int cpu, void *dummy) { return 0; }
 413#define buffer_heads_over_limit 0
 414
 415#endif /* CONFIG_BLOCK */
 416#endif /* _LINUX_BUFFER_HEAD_H */
 417
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