buffer_head.h

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/*
 * include/linux/buffer_head.h
 *
 * Everything to do with buffer_heads.
 */

#ifndef _LINUX_BUFFER_HEAD_H
#define _LINUX_BUFFER_HEAD_H

#include <linux/types.h>
#include <linux/fs.h>
#include <linux/linkage.h>
#include <linux/pagemap.h>
#include <linux/wait.h>
#include <linux/atomic.h>

#ifdef CONFIG_BLOCK

enum bh_state_bits {
    BH_Uptodate,    /* Contains valid data */
    BH_Dirty,   /* Is dirty */
    BH_Lock,    /* Is locked */
    BH_Req,     /* Has been submitted for I/O */
    BH_Uptodate_Lock,/* Used by the first bh in a page, to serialise
              * IO completion of other buffers in the page
              */

    BH_Mapped,  /* Has a disk mapping */
    BH_New,     /* Disk mapping was newly created by get_block */
    BH_Async_Read,  /* Is under end_buffer_async_read I/O */
    BH_Async_Write, /* Is under end_buffer_async_write I/O */
    BH_Delay,   /* Buffer is not yet allocated on disk */
    BH_Boundary,    /* Block is followed by a discontiguity */
    BH_Write_EIO,   /* I/O error on write */
    BH_Unwritten,   /* Buffer is allocated on disk but not written */
    BH_Quiet,   /* Buffer Error Prinks to be quiet */

    BH_PrivateStart,/* not a state bit, but the first bit available
             * for private allocation by other entities
             */
};

#define MAX_BUF_PER_PAGE (PAGE_CACHE_SIZE / 512)

struct page;
struct buffer_head;
struct address_space;
typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);

/*
 * Historically, a buffer_head was used to map a single block
 * within a page, and of course as the unit of I/O through the
 * filesystem and block layers.  Nowadays the basic I/O unit
 * is the bio, and buffer_heads are used for extracting block
 * mappings (via a get_block_t call), for tracking state within
 * a page (via a page_mapping) and for wrapping bio submission
 * for backward compatibility reasons (e.g. submit_bh).
 */
struct buffer_head {
    unsigned long b_state;      /* buffer state bitmap (see above) */
    struct buffer_head *b_this_page;/* circular list of page's buffers */
    struct page *b_page;        /* the page this bh is mapped to */

    sector_t b_blocknr;     /* start block number */
    size_t b_size;          /* size of mapping */
    char *b_data;           /* pointer to data within the page */

    struct block_device *b_bdev;
    bh_end_io_t *b_end_io;      /* I/O completion */
    void *b_private;        /* reserved for b_end_io */
    struct list_head b_assoc_buffers; /* associated with another mapping */
    struct address_space *b_assoc_map;  /* mapping this buffer is
                           associated with */
    atomic_t b_count;       /* users using this buffer_head */
};

/*
 * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
 * and buffer_foo() functions.
 */
#define BUFFER_FNS(bit, name)                       \
static inline void set_buffer_##name(struct buffer_head *bh)        \
{                                   \
    set_bit(BH_##bit, &(bh)->b_state);              \
}                                   \
static inline void clear_buffer_##name(struct buffer_head *bh)      \
{                                   \
    clear_bit(BH_##bit, &(bh)->b_state);                \
}                                   \
static inline int buffer_##name(const struct buffer_head *bh)       \
{                                   \
    return test_bit(BH_##bit, &(bh)->b_state);          \
}

/*
 * test_set_buffer_foo() and test_clear_buffer_foo()
 */
#define TAS_BUFFER_FNS(bit, name)                   \
static inline int test_set_buffer_##name(struct buffer_head *bh)    \
{                                   \
    return test_and_set_bit(BH_##bit, &(bh)->b_state);      \
}                                   \
static inline int test_clear_buffer_##name(struct buffer_head *bh)  \
{                                   \
    return test_and_clear_bit(BH_##bit, &(bh)->b_state);        \
}                                   \

/*
 * Emit the buffer bitops functions.   Note that there are also functions
 * of the form "mark_buffer_foo()".  These are higher-level functions which
 * do something in addition to setting a b_state bit.
 */
BUFFER_FNS(Uptodate, uptodate)
BUFFER_FNS(Dirty, dirty)
TAS_BUFFER_FNS(Dirty, dirty)
BUFFER_FNS(Lock, locked)
BUFFER_FNS(Req, req)
TAS_BUFFER_FNS(Req, req)
BUFFER_FNS(Mapped, mapped)
BUFFER_FNS(New, new)
BUFFER_FNS(Async_Read, async_read)
BUFFER_FNS(Async_Write, async_write)
BUFFER_FNS(Delay, delay)
BUFFER_FNS(Boundary, boundary)
BUFFER_FNS(Write_EIO, write_io_error)
BUFFER_FNS(Unwritten, unwritten)

#define bh_offset(bh)       ((unsigned long)(bh)->b_data & ~PAGE_MASK)
#define touch_buffer(bh)    mark_page_accessed(bh->b_page)

/* If we *know* page->private refers to buffer_heads */
#define page_buffers(page)                  \
    ({                          \
        BUG_ON(!PagePrivate(page));         \
        ((struct buffer_head *)page_private(page)); \
    })
#define page_has_buffers(page)  PagePrivate(page)

/*
 * Declarations
 */

void mark_buffer_dirty(struct buffer_head *bh);
void init_buffer(struct buffer_head *, bh_end_io_t *, void *);
void set_bh_page(struct buffer_head *bh,
        struct page *page, unsigned long offset);
int try_to_free_buffers(struct page *);
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
        int retry);
void create_empty_buffers(struct page *, unsigned long,
            unsigned long b_state);
void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
void end_buffer_async_write(struct buffer_head *bh, int uptodate);

/* Things to do with buffers at mapping->private_list */
void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
int inode_has_buffers(struct inode *);
void invalidate_inode_buffers(struct inode *);
int remove_inode_buffers(struct inode *inode);
int sync_mapping_buffers(struct address_space *mapping);
void unmap_underlying_metadata(struct block_device *bdev, sector_t block);

void mark_buffer_async_write(struct buffer_head *bh);
void __wait_on_buffer(struct buffer_head *);
wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
            unsigned size);
struct buffer_head *__getblk(struct block_device *bdev, sector_t block,
            unsigned size);
void __brelse(struct buffer_head *);
void __bforget(struct buffer_head *);
void __breadahead(struct block_device *, sector_t block, unsigned int size);
struct buffer_head *__bread(struct block_device *, sector_t block, unsigned size);
void invalidate_bh_lrus(void);
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
void free_buffer_head(struct buffer_head * bh);
void unlock_buffer(struct buffer_head *bh);
void __lock_buffer(struct buffer_head *bh);
void ll_rw_block(int, int, struct buffer_head * bh[]);
int sync_dirty_buffer(struct buffer_head *bh);
int __sync_dirty_buffer(struct buffer_head *bh, int rw);
void write_dirty_buffer(struct buffer_head *bh, int rw);
int submit_bh(int, struct buffer_head *);
void write_boundary_block(struct block_device *bdev,
            sector_t bblock, unsigned blocksize);
int bh_uptodate_or_lock(struct buffer_head *bh);
int bh_submit_read(struct buffer_head *bh);

extern int buffer_heads_over_limit;

/*
 * Generic address_space_operations implementations for buffer_head-backed
 * address_spaces.
 */
void block_invalidatepage(struct page *page, unsigned long offset);
int block_write_full_page(struct page *page, get_block_t *get_block,
                struct writeback_control *wbc);
int block_write_full_page_endio(struct page *page, get_block_t *get_block,
            struct writeback_control *wbc, bh_end_io_t *handler);
int block_read_full_page(struct page*, get_block_t*);
int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
                unsigned long from);
int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
        unsigned flags, struct page **pagep, get_block_t *get_block);
int __block_write_begin(struct page *page, loff_t pos, unsigned len,
        get_block_t *get_block);
int block_write_end(struct file *, struct address_space *,
                loff_t, unsigned, unsigned,
                struct page *, void *);
int generic_write_end(struct file *, struct address_space *,
                loff_t, unsigned, unsigned,
                struct page *, void *);
void page_zero_new_buffers(struct page *page, unsigned from, unsigned to);
int cont_write_begin(struct file *, struct address_space *, loff_t,
            unsigned, unsigned, struct page **, void **,
            get_block_t *, loff_t *);
int generic_cont_expand_simple(struct inode *inode, loff_t size);
int block_commit_write(struct page *page, unsigned from, unsigned to);
int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
                get_block_t get_block);
int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
                get_block_t get_block);
/* Convert errno to return value from ->page_mkwrite() call */
static inline int block_page_mkwrite_return(int err)
{
    if (err == 0)
        return VM_FAULT_LOCKED;
    if (err == -EFAULT)
        return VM_FAULT_NOPAGE;
    if (err == -ENOMEM)
        return VM_FAULT_OOM;
    if (err == -EAGAIN)
        return VM_FAULT_RETRY;
    /* -ENOSPC, -EDQUOT, -EIO ... */
    return VM_FAULT_SIGBUS;
}
sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
int block_truncate_page(struct address_space *, loff_t, get_block_t *);
int nobh_write_begin(struct address_space *, loff_t, unsigned, unsigned,
                struct page **, void **, get_block_t*);
int nobh_write_end(struct file *, struct address_space *,
                loff_t, unsigned, unsigned,
                struct page *, void *);
int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
int nobh_writepage(struct page *page, get_block_t *get_block,
                        struct writeback_control *wbc);

void buffer_init(void);

/*
 * inline definitions
 */

static inline void attach_page_buffers(struct page *page,
        struct buffer_head *head)
{
    page_cache_get(page);
    SetPagePrivate(page);
    set_page_private(page, (unsigned long)head);
}

static inline void get_bh(struct buffer_head *bh)
{
        atomic_inc(&bh->b_count);
}

static inline void put_bh(struct buffer_head *bh)
{
        smp_mb__before_atomic_dec();
        atomic_dec(&bh->b_count);
}

static inline void brelse(struct buffer_head *bh)
{
    if (bh)
        __brelse(bh);
}

static inline void bforget(struct buffer_head *bh)
{
    if (bh)
        __bforget(bh);
}

static inline struct buffer_head *
sb_bread(struct super_block *sb, sector_t block)
{
    return __bread(sb->s_bdev, block, sb->s_blocksize);
}

static inline void
sb_breadahead(struct super_block *sb, sector_t block)
{
    __breadahead(sb->s_bdev, block, sb->s_blocksize);
}

static inline struct buffer_head *
sb_getblk(struct super_block *sb, sector_t block)
{
    return __getblk(sb->s_bdev, block, sb->s_blocksize);
}

static inline struct buffer_head *
sb_find_get_block(struct super_block *sb, sector_t block)
{
    return __find_get_block(sb->s_bdev, block, sb->s_blocksize);
}

static inline void
map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
{
    set_buffer_mapped(bh);
    bh->b_bdev = sb->s_bdev;
    bh->b_blocknr = block;
    bh->b_size = sb->s_blocksize;
}

static inline void wait_on_buffer(struct buffer_head *bh)
{
    might_sleep();
    if (buffer_locked(bh))
        __wait_on_buffer(bh);
}

static inline int trylock_buffer(struct buffer_head *bh)
{
    return likely(!test_and_set_bit_lock(BH_Lock, &bh->b_state));
}

static inline void lock_buffer(struct buffer_head *bh)
{
    might_sleep();
    if (!trylock_buffer(bh))
        __lock_buffer(bh);
}

extern int __set_page_dirty_buffers(struct page *page);

#else /* CONFIG_BLOCK */

static inline void buffer_init(void) {}
static inline int try_to_free_buffers(struct page *page) { return 1; }
static inline int inode_has_buffers(struct inode *inode) { return 0; }
static inline void invalidate_inode_buffers(struct inode *inode) {}
static inline int remove_inode_buffers(struct inode *inode) { return 1; }
static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }

#endif /* CONFIG_BLOCK */
#endif /* _LINUX_BUFFER_HEAD_H */