/*
 * 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 <asm/atomic.h>

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_Ordered,     /* ordered write */
        BH_Eopnotsupp,  /* operation not supported (barrier) */

        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 */
        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)
TAS_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(Ordered, ordered)
BUFFER_FNS(Eopnotsupp, eopnotsupp)

#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 FASTCALL(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);

/* 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 invalidate_bdev(struct block_device *, int);
int sync_blockdev(struct block_device *bdev);
void __wait_on_buffer(struct buffer_head *);
wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
int fsync_bdev(struct block_device *);
struct super_block *freeze_bdev(struct block_device *);
void thaw_bdev(struct block_device *, struct super_block *);
int fsync_super(struct super_block *);
int fsync_no_super(struct block_device *);
struct buffer_head *__find_get_block(struct block_device *, sector_t, int);
struct buffer_head * __getblk(struct block_device *, sector_t, int);
void __brelse(struct buffer_head *);
void __bforget(struct buffer_head *);
void __breadahead(struct block_device *, sector_t block, int size);
struct buffer_head *__bread(struct block_device *, sector_t block, int size);
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
void free_buffer_head(struct buffer_head * bh);
void FASTCALL(unlock_buffer(struct buffer_head *bh));
void FASTCALL(__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 submit_bh(int, struct buffer_head *);
void write_boundary_block(struct block_device *bdev,
                        sector_t bblock, unsigned blocksize);

extern int buffer_heads_over_limit;

/*
 * Generic address_space_operations implementations for buffer_head-backed
 * address_spaces.
 */
int try_to_release_page(struct page * page, gfp_t gfp_mask);
void block_invalidatepage(struct page *page, unsigned long offset);
void do_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_read_full_page(struct page*, get_block_t*);
int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*,
                                loff_t *);
int generic_cont_expand(struct inode *inode, loff_t size);
int generic_cont_expand_simple(struct inode *inode, loff_t size);
int block_commit_write(struct page *page, unsigned from, unsigned to);
void block_sync_page(struct page *);
sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
int generic_commit_write(struct file *, struct page *, unsigned, unsigned);
int block_truncate_page(struct address_space *, loff_t, get_block_t *);
int file_fsync(struct file *, struct dentry *, int);
int nobh_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
int nobh_commit_write(struct file *, struct page *, unsigned, unsigned);
int nobh_truncate_page(struct address_space *, loff_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;
}

/*
 * Calling wait_on_buffer() for a zero-ref buffer is illegal, so we call into
 * __wait_on_buffer() just to trip a debug check.  Because debug code in inline
 * functions is bloaty.
 */
static inline void wait_on_buffer(struct buffer_head *bh)
{
        might_sleep();
        if (buffer_locked(bh) || atomic_read(&bh->b_count) == 0)
                __wait_on_buffer(bh);
}

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

#endif /* _LINUX_BUFFER_HEAD_H */