xfs_buf.h

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/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#ifndef __XFS_BUF_H__
#define __XFS_BUF_H__

#include <linux/list.h>
#include <linux/types.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/uio.h>

/*
 *  Base types
 */

#define XFS_BUF_DADDR_NULL  ((xfs_daddr_t) (-1LL))

typedef enum {
    XBRW_READ = 1,          /* transfer into target memory */
    XBRW_WRITE = 2,         /* transfer from target memory */
    XBRW_ZERO = 3,          /* Zero target memory */
} xfs_buf_rw_t;

#define XBF_READ     (1 << 0) /* buffer intended for reading from device */
#define XBF_WRITE    (1 << 1) /* buffer intended for writing to device */
#define XBF_READ_AHEAD   (1 << 2) /* asynchronous read-ahead */
#define XBF_ASYNC    (1 << 4) /* initiator will not wait for completion */
#define XBF_DONE     (1 << 5) /* all pages in the buffer uptodate */
#define XBF_STALE    (1 << 6) /* buffer has been staled, do not find it */

/* I/O hints for the BIO layer */
#define XBF_SYNCIO   (1 << 10)/* treat this buffer as synchronous I/O */
#define XBF_FUA      (1 << 11)/* force cache write through mode */
#define XBF_FLUSH    (1 << 12)/* flush the disk cache before a write */

/* flags used only as arguments to access routines */
#define XBF_TRYLOCK  (1 << 16)/* lock requested, but do not wait */
#define XBF_UNMAPPED     (1 << 17)/* do not map the buffer */

/* flags used only internally */
#define _XBF_PAGES   (1 << 20)/* backed by refcounted pages */
#define _XBF_KMEM    (1 << 21)/* backed by heap memory */
#define _XBF_DELWRI_Q    (1 << 22)/* buffer on a delwri queue */
#define _XBF_COMPOUND    (1 << 23)/* compound buffer */
#define _XBF_LRU_DISPOSE (1 << 24)/* buffer being discarded */

typedef unsigned int xfs_buf_flags_t;

#define XFS_BUF_FLAGS \
    { XBF_READ,     "READ" }, \
    { XBF_WRITE,        "WRITE" }, \
    { XBF_READ_AHEAD,   "READ_AHEAD" }, \
    { XBF_ASYNC,        "ASYNC" }, \
    { XBF_DONE,     "DONE" }, \
    { XBF_STALE,        "STALE" }, \
    { XBF_SYNCIO,       "SYNCIO" }, \
    { XBF_FUA,      "FUA" }, \
    { XBF_FLUSH,        "FLUSH" }, \
    { XBF_TRYLOCK,      "TRYLOCK" },    /* should never be set */\
    { XBF_UNMAPPED,     "UNMAPPED" },   /* ditto */\
    { _XBF_PAGES,       "PAGES" }, \
    { _XBF_KMEM,        "KMEM" }, \
    { _XBF_DELWRI_Q,    "DELWRI_Q" }, \
    { _XBF_COMPOUND,    "COMPOUND" }, \
    { _XBF_LRU_DISPOSE, "LRU_DISPOSE" }

typedef struct xfs_buftarg {
    dev_t           bt_dev;
    struct block_device *bt_bdev;
    struct backing_dev_info *bt_bdi;
    struct xfs_mount    *bt_mount;
    unsigned int        bt_bsize;
    unsigned int        bt_sshift;
    size_t          bt_smask;

    /* LRU control structures */
    struct shrinker     bt_shrinker;
    struct list_head    bt_lru;
    spinlock_t      bt_lru_lock;
    unsigned int        bt_lru_nr;
} xfs_buftarg_t;

struct xfs_buf;
typedef void (*xfs_buf_iodone_t)(struct xfs_buf *);

#define XB_PAGES    2

struct xfs_buf_map {
    xfs_daddr_t     bm_bn;  /* block number for I/O */
    int         bm_len; /* size of I/O */
};

#define DEFINE_SINGLE_BUF_MAP(map, blkno, numblk) \
    struct xfs_buf_map (map) = { .bm_bn = (blkno), .bm_len = (numblk) };

typedef struct xfs_buf {
    /*
     * first cacheline holds all the fields needed for an uncontended cache
     * hit to be fully processed. The semaphore straddles the cacheline
     * boundary, but the counter and lock sits on the first cacheline,
     * which is the only bit that is touched if we hit the semaphore
     * fast-path on locking.
     */
    struct rb_node      b_rbnode;   /* rbtree node */
    xfs_daddr_t     b_bn;       /* block number of buffer */
    int         b_length;   /* size of buffer in BBs */
    atomic_t        b_hold;     /* reference count */
    atomic_t        b_lru_ref;  /* lru reclaim ref count */
    xfs_buf_flags_t     b_flags;    /* status flags */
    struct semaphore    b_sema;     /* semaphore for lockables */

    /*
     * concurrent access to b_lru and b_lru_flags are protected by
     * bt_lru_lock and not by b_sema
     */
    struct list_head    b_lru;      /* lru list */
    xfs_buf_flags_t     b_lru_flags;    /* internal lru status flags */
    wait_queue_head_t   b_waiters;  /* unpin waiters */
    struct list_head    b_list;
    struct xfs_perag    *b_pag;     /* contains rbtree root */
    xfs_buftarg_t       *b_target;  /* buffer target (device) */
    void            *b_addr;    /* virtual address of buffer */
    struct work_struct  b_iodone_work;
    xfs_buf_iodone_t    b_iodone;   /* I/O completion function */
    struct completion   b_iowait;   /* queue for I/O waiters */
    void            *b_fspriv;
    struct xfs_trans    *b_transp;
    struct page     **b_pages;  /* array of page pointers */
    struct page     *b_page_array[XB_PAGES]; /* inline pages */
    struct xfs_buf_map  *b_maps;    /* compound buffer map */
    struct xfs_buf_map  b_map;      /* inline compound buffer map */
    int         b_map_count;
    int         b_io_length;    /* IO size in BBs */
    atomic_t        b_pin_count;    /* pin count */
    atomic_t        b_io_remaining; /* #outstanding I/O requests */
    unsigned int        b_page_count;   /* size of page array */
    unsigned int        b_offset;   /* page offset in first page */
    unsigned short      b_error;    /* error code on I/O */

#ifdef XFS_BUF_LOCK_TRACKING
    int         b_last_holder;
#endif
} xfs_buf_t;


/* Finding and Reading Buffers */
struct xfs_buf *_xfs_buf_find(struct xfs_buftarg *target,
                  struct xfs_buf_map *map, int nmaps,
                  xfs_buf_flags_t flags, struct xfs_buf *new_bp);

static inline struct xfs_buf *
xfs_incore(
    struct xfs_buftarg  *target,
    xfs_daddr_t     blkno,
    size_t          numblks,
    xfs_buf_flags_t     flags)
{
    DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
    return _xfs_buf_find(target, &map, 1, flags, NULL);
}

struct xfs_buf *_xfs_buf_alloc(struct xfs_buftarg *target,
                   struct xfs_buf_map *map, int nmaps,
                   xfs_buf_flags_t flags);

static inline struct xfs_buf *
xfs_buf_alloc(
    struct xfs_buftarg  *target,
    xfs_daddr_t     blkno,
    size_t          numblks,
    xfs_buf_flags_t     flags)
{
    DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
    return _xfs_buf_alloc(target, &map, 1, flags);
}

struct xfs_buf *xfs_buf_get_map(struct xfs_buftarg *target,
                   struct xfs_buf_map *map, int nmaps,
                   xfs_buf_flags_t flags);
struct xfs_buf *xfs_buf_read_map(struct xfs_buftarg *target,
                   struct xfs_buf_map *map, int nmaps,
                   xfs_buf_flags_t flags);
void xfs_buf_readahead_map(struct xfs_buftarg *target,
                   struct xfs_buf_map *map, int nmaps);

static inline struct xfs_buf *
xfs_buf_get(
    struct xfs_buftarg  *target,
    xfs_daddr_t     blkno,
    size_t          numblks,
    xfs_buf_flags_t     flags)
{
    DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
    return xfs_buf_get_map(target, &map, 1, flags);
}

static inline struct xfs_buf *
xfs_buf_read(
    struct xfs_buftarg  *target,
    xfs_daddr_t     blkno,
    size_t          numblks,
    xfs_buf_flags_t     flags)
{
    DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
    return xfs_buf_read_map(target, &map, 1, flags);
}

static inline void
xfs_buf_readahead(
    struct xfs_buftarg  *target,
    xfs_daddr_t     blkno,
    size_t          numblks)
{
    DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
    return xfs_buf_readahead_map(target, &map, 1);
}

struct xfs_buf *xfs_buf_get_empty(struct xfs_buftarg *target, size_t numblks);
void xfs_buf_set_empty(struct xfs_buf *bp, size_t numblks);
int xfs_buf_associate_memory(struct xfs_buf *bp, void *mem, size_t length);

struct xfs_buf *xfs_buf_get_uncached(struct xfs_buftarg *target, size_t numblks,
                int flags);
struct xfs_buf *xfs_buf_read_uncached(struct xfs_buftarg *target,
                xfs_daddr_t daddr, size_t numblks, int flags);
void xfs_buf_hold(struct xfs_buf *bp);

/* Releasing Buffers */
extern void xfs_buf_free(xfs_buf_t *);
extern void xfs_buf_rele(xfs_buf_t *);

/* Locking and Unlocking Buffers */
extern int xfs_buf_trylock(xfs_buf_t *);
extern void xfs_buf_lock(xfs_buf_t *);
extern void xfs_buf_unlock(xfs_buf_t *);
#define xfs_buf_islocked(bp) \
    ((bp)->b_sema.count <= 0)

/* Buffer Read and Write Routines */
extern int xfs_bwrite(struct xfs_buf *bp);

extern void xfsbdstrat(struct xfs_mount *, struct xfs_buf *);

extern void xfs_buf_ioend(xfs_buf_t *,  int);
extern void xfs_buf_ioerror(xfs_buf_t *, int);
extern void xfs_buf_ioerror_alert(struct xfs_buf *, const char *func);
extern void xfs_buf_iorequest(xfs_buf_t *);
extern int xfs_buf_iowait(xfs_buf_t *);
extern void xfs_buf_iomove(xfs_buf_t *, size_t, size_t, void *,
                xfs_buf_rw_t);
#define xfs_buf_zero(bp, off, len) \
        xfs_buf_iomove((bp), (off), (len), NULL, XBRW_ZERO)

static inline int xfs_buf_geterror(xfs_buf_t *bp)
{
    return bp ? bp->b_error : ENOMEM;
}

/* Buffer Utility Routines */
extern xfs_caddr_t xfs_buf_offset(xfs_buf_t *, size_t);

/* Delayed Write Buffer Routines */
extern bool xfs_buf_delwri_queue(struct xfs_buf *, struct list_head *);
extern int xfs_buf_delwri_submit(struct list_head *);
extern int xfs_buf_delwri_submit_nowait(struct list_head *);

/* Buffer Daemon Setup Routines */
extern int xfs_buf_init(void);
extern void xfs_buf_terminate(void);

#define XFS_BUF_ZEROFLAGS(bp) \
    ((bp)->b_flags &= ~(XBF_READ|XBF_WRITE|XBF_ASYNC| \
                XBF_SYNCIO|XBF_FUA|XBF_FLUSH))

void xfs_buf_stale(struct xfs_buf *bp);
#define XFS_BUF_UNSTALE(bp) ((bp)->b_flags &= ~XBF_STALE)
#define XFS_BUF_ISSTALE(bp) ((bp)->b_flags & XBF_STALE)

#define XFS_BUF_DONE(bp)    ((bp)->b_flags |= XBF_DONE)
#define XFS_BUF_UNDONE(bp)  ((bp)->b_flags &= ~XBF_DONE)
#define XFS_BUF_ISDONE(bp)  ((bp)->b_flags & XBF_DONE)

#define XFS_BUF_ASYNC(bp)   ((bp)->b_flags |= XBF_ASYNC)
#define XFS_BUF_UNASYNC(bp) ((bp)->b_flags &= ~XBF_ASYNC)
#define XFS_BUF_ISASYNC(bp) ((bp)->b_flags & XBF_ASYNC)

#define XFS_BUF_READ(bp)    ((bp)->b_flags |= XBF_READ)
#define XFS_BUF_UNREAD(bp)  ((bp)->b_flags &= ~XBF_READ)
#define XFS_BUF_ISREAD(bp)  ((bp)->b_flags & XBF_READ)

#define XFS_BUF_WRITE(bp)   ((bp)->b_flags |= XBF_WRITE)
#define XFS_BUF_UNWRITE(bp) ((bp)->b_flags &= ~XBF_WRITE)
#define XFS_BUF_ISWRITE(bp) ((bp)->b_flags & XBF_WRITE)

/*
 * These macros use the IO block map rather than b_bn. b_bn is now really
 * just for the buffer cache index for cached buffers. As IO does not use b_bn
 * anymore, uncached buffers do not use b_bn at all and hence must modify the IO
 * map directly. Uncached buffers are not allowed to be discontiguous, so this
 * is safe to do.
 *
 * In future, uncached buffers will pass the block number directly to the io
 * request function and hence these macros will go away at that point.
 */
#define XFS_BUF_ADDR(bp)        ((bp)->b_map.bm_bn)
#define XFS_BUF_SET_ADDR(bp, bno)   ((bp)->b_map.bm_bn = (xfs_daddr_t)(bno))

static inline void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
{
    atomic_set(&bp->b_lru_ref, lru_ref);
}

static inline int xfs_buf_ispinned(struct xfs_buf *bp)
{
    return atomic_read(&bp->b_pin_count);
}

static inline void xfs_buf_relse(xfs_buf_t *bp)
{
    xfs_buf_unlock(bp);
    xfs_buf_rele(bp);
}

/*
 *  Handling of buftargs.
 */
extern xfs_buftarg_t *xfs_alloc_buftarg(struct xfs_mount *,
            struct block_device *, int, const char *);
extern void xfs_free_buftarg(struct xfs_mount *, struct xfs_buftarg *);
extern void xfs_wait_buftarg(xfs_buftarg_t *);
extern int xfs_setsize_buftarg(xfs_buftarg_t *, unsigned int, unsigned int);

#define xfs_getsize_buftarg(buftarg)    block_size((buftarg)->bt_bdev)
#define xfs_readonly_buftarg(buftarg)   bdev_read_only((buftarg)->bt_bdev)

#endif  /* __XFS_BUF_H__ */