[mirror_ubuntu-zesty-kernel.git] / fs / xfs / xfs_buf.h

/*
 * 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/dax.h>
#include <linux/buffer_head.h>
#include <linux/uio.h>
#include <linux/list_lru.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_NO_IOACCT	 (1 << 3) /* bypass I/O accounting (non-LRU bufs) */
#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 */
#define XBF_WRITE_FAIL	 (1 << 24)/* async writes have failed on this buffer */

/* 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_IN_FLIGHT	 (1 << 25) /* I/O in flight, for accounting purposes */

typedef unsigned int xfs_buf_flags_t;

#define XFS_BUF_FLAGS \
	{ XBF_READ,		"READ" }, \
	{ XBF_WRITE,		"WRITE" }, \
	{ XBF_READ_AHEAD,	"READ_AHEAD" }, \
	{ XBF_NO_IOACCT,	"NO_IOACCT" }, \
	{ XBF_ASYNC,		"ASYNC" }, \
	{ XBF_DONE,		"DONE" }, \
	{ XBF_STALE,		"STALE" }, \
	{ XBF_WRITE_FAIL,	"WRITE_FAIL" }, \
	{ 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_IN_FLIGHT,	"IN_FLIGHT" }


/*
 * Internal state flags.
 */
#define XFS_BSTATE_DISPOSE	 (1 << 0)	/* buffer being discarded */

/*
 * The xfs_buftarg contains 2 notions of "sector size" -
 *
 * 1) The metadata sector size, which is the minimum unit and
 *    alignment of IO which will be performed by metadata operations.
 * 2) The device logical sector size
 *
 * The first is specified at mkfs time, and is stored on-disk in the
 * superblock's sb_sectsize.
 *
 * The latter is derived from the underlying device, and controls direct IO
 * alignment constraints.
 */
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_meta_sectorsize;
	size_t			bt_meta_sectormask;
	size_t			bt_logical_sectorsize;
	size_t			bt_logical_sectormask;

	/* LRU control structures */
	struct shrinker		bt_shrinker;
	struct list_lru		bt_lru;

	struct percpu_counter	bt_io_count;
} 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) };

struct xfs_buf_ops {
	char *name;
	void (*verify_read)(struct xfs_buf *);
	void (*verify_write)(struct xfs_buf *);
};

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 rhash_head	b_rhash_head;	/* pag buffer hash 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 */
	spinlock_t		b_lock;		/* internal state lock */
	unsigned int		b_state;	/* internal state flags */
	int			b_io_error;	/* internal IO error state */
	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_ioend_work;
	struct workqueue_struct	*b_ioend_wq;	/* I/O completion wq */
	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 */
	int			b_error;	/* error code on I/O */

	/*
	 * async write failure retry count. Initialised to zero on the first
	 * failure, then when it exceeds the maximum configured without a
	 * success the write is considered to be failed permanently and the
	 * iodone handler will take appropriate action.
	 *
	 * For retry timeouts, we record the jiffie of the first failure. This
	 * means that we can change the retry timeout for buffers already under
	 * I/O and thus avoid getting stuck in a retry loop with a long timeout.
	 *
	 * last_error is used to ensure that we are getting repeated errors, not
	 * different errors. e.g. a block device might change ENOSPC to EIO when
	 * a failure timeout occurs, so we want to re-initialise the error
	 * retry behaviour appropriately when that happens.
	 */
	int			b_retries;
	unsigned long		b_first_retry_time; /* in jiffies */
	int			b_last_error;

	const struct xfs_buf_ops	*b_ops;

#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,
			       const struct xfs_buf_ops *ops);
void xfs_buf_readahead_map(struct xfs_buftarg *target,
			       struct xfs_buf_map *map, int nmaps,
			       const struct xfs_buf_ops *ops);

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,
	const struct xfs_buf_ops *ops)
{
	DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
	return xfs_buf_read_map(target, &map, 1, flags, ops);
}

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

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);
int xfs_buf_read_uncached(struct xfs_buftarg *target, xfs_daddr_t daddr,
			  size_t numblks, int flags, struct xfs_buf **bpp,
			  const struct xfs_buf_ops *ops);
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 xfs_buf_ioend(struct xfs_buf *bp);
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_submit(struct xfs_buf *bp);
extern int xfs_buf_submit_wait(struct xfs_buf *bp);
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)

/* Buffer Utility Routines */
extern void *xfs_buf_offset(struct xfs_buf *, size_t);
extern void xfs_buf_stale(struct xfs_buf *bp);

/* 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);

/*
 * 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_maps[0].bm_bn)
#define XFS_BUF_SET_ADDR(bp, bno)	((bp)->b_maps[0].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);
}

static inline int
xfs_buf_verify_cksum(struct xfs_buf *bp, unsigned long cksum_offset)
{
	return xfs_verify_cksum(bp->b_addr, BBTOB(bp->b_length),
				cksum_offset);
}

static inline void
xfs_buf_update_cksum(struct xfs_buf *bp, unsigned long cksum_offset)
{
	xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length),
			 cksum_offset);
}

/*
 *	Handling of buftargs.
 */
extern xfs_buftarg_t *xfs_alloc_buftarg(struct xfs_mount *,
			struct block_device *);
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);

#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__ */
Commit	Line	Data
	1	/*
	2	* Copyright (c) 2000-2005 Silicon Graphics, Inc.
	3	* All Rights Reserved.
	4	*
	5	* This program is free software; you can redistribute it and/or
	6	* modify it under the terms of the GNU General Public License as
	7	* published by the Free Software Foundation.
	8	*
	9	* This program is distributed in the hope that it would be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; if not, write the Free Software Foundation,
	16	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	17	*/
	18	#ifndef __XFS_BUF_H__
	19	#define __XFS_BUF_H__
	20
	21	#include <linux/list.h>
	22	#include <linux/types.h>
	23	#include <linux/spinlock.h>
	24	#include <linux/mm.h>
	25	#include <linux/fs.h>
	26	#include <linux/dax.h>
	27	#include <linux/buffer_head.h>
	28	#include <linux/uio.h>
	29	#include <linux/list_lru.h>
	30
	31	/*
	32	* Base types
	33	*/
	34
	35	#define XFS_BUF_DADDR_NULL ((xfs_daddr_t) (-1LL))
	36
	37	typedef enum {
	38	XBRW_READ = 1, /* transfer into target memory */
	39	XBRW_WRITE = 2, /* transfer from target memory */
	40	XBRW_ZERO = 3, /* Zero target memory */
	41	} xfs_buf_rw_t;
	42
	43	#define XBF_READ (1 << 0) /* buffer intended for reading from device */
	44	#define XBF_WRITE (1 << 1) /* buffer intended for writing to device */
	45	#define XBF_READ_AHEAD (1 << 2) /* asynchronous read-ahead */
	46	#define XBF_NO_IOACCT (1 << 3) /* bypass I/O accounting (non-LRU bufs) */
	47	#define XBF_ASYNC (1 << 4) /* initiator will not wait for completion */
	48	#define XBF_DONE (1 << 5) /* all pages in the buffer uptodate */
	49	#define XBF_STALE (1 << 6) /* buffer has been staled, do not find it */
	50	#define XBF_WRITE_FAIL (1 << 24)/* async writes have failed on this buffer */
	51
	52	/* I/O hints for the BIO layer */
	53	#define XBF_SYNCIO (1 << 10)/* treat this buffer as synchronous I/O */
	54	#define XBF_FUA (1 << 11)/* force cache write through mode */
	55	#define XBF_FLUSH (1 << 12)/* flush the disk cache before a write */
	56
	57	/* flags used only as arguments to access routines */
	58	#define XBF_TRYLOCK (1 << 16)/* lock requested, but do not wait */
	59	#define XBF_UNMAPPED (1 << 17)/* do not map the buffer */
	60
	61	/* flags used only internally */
	62	#define _XBF_PAGES (1 << 20)/* backed by refcounted pages */
	63	#define _XBF_KMEM (1 << 21)/* backed by heap memory */
	64	#define _XBF_DELWRI_Q (1 << 22)/* buffer on a delwri queue */
	65	#define _XBF_COMPOUND (1 << 23)/* compound buffer */
	66	#define _XBF_IN_FLIGHT (1 << 25) /* I/O in flight, for accounting purposes */
	67
	68	typedef unsigned int xfs_buf_flags_t;
	69
	70	#define XFS_BUF_FLAGS \
	71	{ XBF_READ, "READ" }, \
	72	{ XBF_WRITE, "WRITE" }, \
	73	{ XBF_READ_AHEAD, "READ_AHEAD" }, \
	74	{ XBF_NO_IOACCT, "NO_IOACCT" }, \
	75	{ XBF_ASYNC, "ASYNC" }, \
	76	{ XBF_DONE, "DONE" }, \
	77	{ XBF_STALE, "STALE" }, \
	78	{ XBF_WRITE_FAIL, "WRITE_FAIL" }, \
	79	{ XBF_SYNCIO, "SYNCIO" }, \
	80	{ XBF_FUA, "FUA" }, \
	81	{ XBF_FLUSH, "FLUSH" }, \
	82	{ XBF_TRYLOCK, "TRYLOCK" }, /* should never be set */\
	83	{ XBF_UNMAPPED, "UNMAPPED" }, /* ditto */\
	84	{ _XBF_PAGES, "PAGES" }, \
	85	{ _XBF_KMEM, "KMEM" }, \
	86	{ _XBF_DELWRI_Q, "DELWRI_Q" }, \
	87	{ _XBF_COMPOUND, "COMPOUND" }, \
	88	{ _XBF_IN_FLIGHT, "IN_FLIGHT" }
	89
	90
	91	/*
	92	* Internal state flags.
	93	*/
	94	#define XFS_BSTATE_DISPOSE (1 << 0) /* buffer being discarded */
	95
	96	/*
	97	* The xfs_buftarg contains 2 notions of "sector size" -
	98	*
	99	* 1) The metadata sector size, which is the minimum unit and
	100	* alignment of IO which will be performed by metadata operations.
	101	* 2) The device logical sector size
	102	*
	103	* The first is specified at mkfs time, and is stored on-disk in the
	104	* superblock's sb_sectsize.
	105	*
	106	* The latter is derived from the underlying device, and controls direct IO
	107	* alignment constraints.
	108	*/
	109	typedef struct xfs_buftarg {
	110	dev_t bt_dev;
	111	struct block_device *bt_bdev;
	112	struct backing_dev_info *bt_bdi;
	113	struct xfs_mount *bt_mount;
	114	unsigned int bt_meta_sectorsize;
	115	size_t bt_meta_sectormask;
	116	size_t bt_logical_sectorsize;
	117	size_t bt_logical_sectormask;
	118
	119	/* LRU control structures */
	120	struct shrinker bt_shrinker;
	121	struct list_lru bt_lru;
	122
	123	struct percpu_counter bt_io_count;
	124	} xfs_buftarg_t;
	125
	126	struct xfs_buf;
	127	typedef void (xfs_buf_iodone_t)(struct xfs_buf );
	128
	129
	130	#define XB_PAGES 2
	131
	132	struct xfs_buf_map {
	133	xfs_daddr_t bm_bn; /* block number for I/O */
	134	int bm_len; /* size of I/O */
	135	};
	136
	137	#define DEFINE_SINGLE_BUF_MAP(map, blkno, numblk) \
	138	struct xfs_buf_map (map) = { .bm_bn = (blkno), .bm_len = (numblk) };
	139
	140	struct xfs_buf_ops {
	141	char *name;
	142	void (verify_read)(struct xfs_buf );
	143	void (verify_write)(struct xfs_buf );
	144	};
	145
	146	typedef struct xfs_buf {
	147	/*
	148	* first cacheline holds all the fields needed for an uncontended cache
	149	* hit to be fully processed. The semaphore straddles the cacheline
	150	* boundary, but the counter and lock sits on the first cacheline,
	151	* which is the only bit that is touched if we hit the semaphore
	152	* fast-path on locking.
	153	*/
	154	struct rhash_head b_rhash_head; /* pag buffer hash node */
	155	xfs_daddr_t b_bn; /* block number of buffer */
	156	int b_length; /* size of buffer in BBs */
	157	atomic_t b_hold; /* reference count */
	158	atomic_t b_lru_ref; /* lru reclaim ref count */
	159	xfs_buf_flags_t b_flags; /* status flags */
	160	struct semaphore b_sema; /* semaphore for lockables */
	161
	162	/*
	163	* concurrent access to b_lru and b_lru_flags are protected by
	164	* bt_lru_lock and not by b_sema
	165	*/
	166	struct list_head b_lru; /* lru list */
	167	spinlock_t b_lock; /* internal state lock */
	168	unsigned int b_state; /* internal state flags */
	169	int b_io_error; /* internal IO error state */
	170	wait_queue_head_t b_waiters; /* unpin waiters */
	171	struct list_head b_list;
	172	struct xfs_perag b_pag; / contains rbtree root */
	173	xfs_buftarg_t b_target; / buffer target (device) */
	174	void b_addr; / virtual address of buffer */
	175	struct work_struct b_ioend_work;
	176	struct workqueue_struct b_ioend_wq; / I/O completion wq */
	177	xfs_buf_iodone_t b_iodone; /* I/O completion function */
	178	struct completion b_iowait; /* queue for I/O waiters */
	179	void *b_fspriv;
	180	struct xfs_trans *b_transp;
	181	struct page *b_pages; / array of page pointers */
	182	struct page b_page_array[XB_PAGES]; / inline pages */
	183	struct xfs_buf_map b_maps; / compound buffer map */
	184	struct xfs_buf_map __b_map; /* inline compound buffer map */
	185	int b_map_count;
	186	int b_io_length; /* IO size in BBs */
	187	atomic_t b_pin_count; /* pin count */
	188	atomic_t b_io_remaining; /* #outstanding I/O requests */
	189	unsigned int b_page_count; /* size of page array */
	190	unsigned int b_offset; /* page offset in first page */
	191	int b_error; /* error code on I/O */
	192
	193	/*
	194	* async write failure retry count. Initialised to zero on the first
	195	* failure, then when it exceeds the maximum configured without a
	196	* success the write is considered to be failed permanently and the
	197	* iodone handler will take appropriate action.
	198	*
	199	* For retry timeouts, we record the jiffie of the first failure. This
	200	* means that we can change the retry timeout for buffers already under
	201	* I/O and thus avoid getting stuck in a retry loop with a long timeout.
	202	*
	203	* last_error is used to ensure that we are getting repeated errors, not
	204	* different errors. e.g. a block device might change ENOSPC to EIO when
	205	* a failure timeout occurs, so we want to re-initialise the error
	206	* retry behaviour appropriately when that happens.
	207	*/
	208	int b_retries;
	209	unsigned long b_first_retry_time; /* in jiffies */
	210	int b_last_error;
	211
	212	const struct xfs_buf_ops *b_ops;
	213
	214	#ifdef XFS_BUF_LOCK_TRACKING
	215	int b_last_holder;
	216	#endif
	217	} xfs_buf_t;
	218
	219	/* Finding and Reading Buffers */
	220	struct xfs_buf _xfs_buf_find(struct xfs_buftarg target,
	221	struct xfs_buf_map *map, int nmaps,
	222	xfs_buf_flags_t flags, struct xfs_buf *new_bp);
	223
	224	static inline struct xfs_buf *
	225	xfs_incore(
	226	struct xfs_buftarg *target,
	227	xfs_daddr_t blkno,
	228	size_t numblks,
	229	xfs_buf_flags_t flags)
	230	{
	231	DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
	232	return _xfs_buf_find(target, &map, 1, flags, NULL);
	233	}
	234
	235	struct xfs_buf _xfs_buf_alloc(struct xfs_buftarg target,
	236	struct xfs_buf_map *map, int nmaps,
	237	xfs_buf_flags_t flags);
	238
	239	static inline struct xfs_buf *
	240	xfs_buf_alloc(
	241	struct xfs_buftarg *target,
	242	xfs_daddr_t blkno,
	243	size_t numblks,
	244	xfs_buf_flags_t flags)
	245	{
	246	DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
	247	return _xfs_buf_alloc(target, &map, 1, flags);
	248	}
	249
	250	struct xfs_buf xfs_buf_get_map(struct xfs_buftarg target,
	251	struct xfs_buf_map *map, int nmaps,
	252	xfs_buf_flags_t flags);
	253	struct xfs_buf xfs_buf_read_map(struct xfs_buftarg target,
	254	struct xfs_buf_map *map, int nmaps,
	255	xfs_buf_flags_t flags,
	256	const struct xfs_buf_ops *ops);
	257	void xfs_buf_readahead_map(struct xfs_buftarg *target,
	258	struct xfs_buf_map *map, int nmaps,
	259	const struct xfs_buf_ops *ops);
	260
	261	static inline struct xfs_buf *
	262	xfs_buf_get(
	263	struct xfs_buftarg *target,
	264	xfs_daddr_t blkno,
	265	size_t numblks,
	266	xfs_buf_flags_t flags)
	267	{
	268	DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
	269	return xfs_buf_get_map(target, &map, 1, flags);
	270	}
	271
	272	static inline struct xfs_buf *
	273	xfs_buf_read(
	274	struct xfs_buftarg *target,
	275	xfs_daddr_t blkno,
	276	size_t numblks,
	277	xfs_buf_flags_t flags,
	278	const struct xfs_buf_ops *ops)
	279	{
	280	DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
	281	return xfs_buf_read_map(target, &map, 1, flags, ops);
	282	}
	283
	284	static inline void
	285	xfs_buf_readahead(
	286	struct xfs_buftarg *target,
	287	xfs_daddr_t blkno,
	288	size_t numblks,
	289	const struct xfs_buf_ops *ops)
	290	{
	291	DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
	292	return xfs_buf_readahead_map(target, &map, 1, ops);
	293	}
	294
	295	struct xfs_buf xfs_buf_get_empty(struct xfs_buftarg target, size_t numblks);
	296	void xfs_buf_set_empty(struct xfs_buf *bp, size_t numblks);
	297	int xfs_buf_associate_memory(struct xfs_buf bp, void mem, size_t length);
	298
	299	struct xfs_buf xfs_buf_get_uncached(struct xfs_buftarg target, size_t numblks,
	300	int flags);
	301	int xfs_buf_read_uncached(struct xfs_buftarg *target, xfs_daddr_t daddr,
	302	size_t numblks, int flags, struct xfs_buf **bpp,
	303	const struct xfs_buf_ops *ops);
	304	void xfs_buf_hold(struct xfs_buf *bp);
	305
	306	/* Releasing Buffers */
	307	extern void xfs_buf_free(xfs_buf_t *);
	308	extern void xfs_buf_rele(xfs_buf_t *);
	309
	310	/* Locking and Unlocking Buffers */
	311	extern int xfs_buf_trylock(xfs_buf_t *);
	312	extern void xfs_buf_lock(xfs_buf_t *);
	313	extern void xfs_buf_unlock(xfs_buf_t *);
	314	#define xfs_buf_islocked(bp) \
	315	((bp)->b_sema.count <= 0)
	316
	317	/* Buffer Read and Write Routines */
	318	extern int xfs_bwrite(struct xfs_buf *bp);
	319	extern void xfs_buf_ioend(struct xfs_buf *bp);
	320	extern void xfs_buf_ioerror(xfs_buf_t *, int);
	321	extern void xfs_buf_ioerror_alert(struct xfs_buf , const char func);
	322	extern void xfs_buf_submit(struct xfs_buf *bp);
	323	extern int xfs_buf_submit_wait(struct xfs_buf *bp);
	324	extern void xfs_buf_iomove(xfs_buf_t , size_t, size_t, void ,
	325	xfs_buf_rw_t);
	326	#define xfs_buf_zero(bp, off, len) \
	327	xfs_buf_iomove((bp), (off), (len), NULL, XBRW_ZERO)
	328
	329	/* Buffer Utility Routines */
	330	extern void xfs_buf_offset(struct xfs_buf , size_t);
	331	extern void xfs_buf_stale(struct xfs_buf *bp);
	332
	333	/* Delayed Write Buffer Routines */
	334	extern bool xfs_buf_delwri_queue(struct xfs_buf , struct list_head );
	335	extern int xfs_buf_delwri_submit(struct list_head *);
	336	extern int xfs_buf_delwri_submit_nowait(struct list_head *);
	337
	338	/* Buffer Daemon Setup Routines */
	339	extern int xfs_buf_init(void);
	340	extern void xfs_buf_terminate(void);
	341
	342	/*
	343	* These macros use the IO block map rather than b_bn. b_bn is now really
	344	* just for the buffer cache index for cached buffers. As IO does not use b_bn
	345	* anymore, uncached buffers do not use b_bn at all and hence must modify the IO
	346	* map directly. Uncached buffers are not allowed to be discontiguous, so this
	347	* is safe to do.
	348	*
	349	* In future, uncached buffers will pass the block number directly to the io
	350	* request function and hence these macros will go away at that point.
	351	*/
	352	#define XFS_BUF_ADDR(bp) ((bp)->b_maps[0].bm_bn)
	353	#define XFS_BUF_SET_ADDR(bp, bno) ((bp)->b_maps[0].bm_bn = (xfs_daddr_t)(bno))
	354
	355	static inline void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
	356	{
	357	atomic_set(&bp->b_lru_ref, lru_ref);
	358	}
	359
	360	static inline int xfs_buf_ispinned(struct xfs_buf *bp)
	361	{
	362	return atomic_read(&bp->b_pin_count);
	363	}
	364
	365	static inline void xfs_buf_relse(xfs_buf_t *bp)
	366	{
	367	xfs_buf_unlock(bp);
	368	xfs_buf_rele(bp);
	369	}
	370
	371	static inline int
	372	xfs_buf_verify_cksum(struct xfs_buf *bp, unsigned long cksum_offset)
	373	{
	374	return xfs_verify_cksum(bp->b_addr, BBTOB(bp->b_length),
	375	cksum_offset);
	376	}
	377
	378	static inline void
	379	xfs_buf_update_cksum(struct xfs_buf *bp, unsigned long cksum_offset)
	380	{
	381	xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length),
	382	cksum_offset);
	383	}
	384
	385	/*
	386	* Handling of buftargs.
	387	*/
	388	extern xfs_buftarg_t xfs_alloc_buftarg(struct xfs_mount ,
	389	struct block_device *);
	390	extern void xfs_free_buftarg(struct xfs_mount , struct xfs_buftarg );
	391	extern void xfs_wait_buftarg(xfs_buftarg_t *);
	392	extern int xfs_setsize_buftarg(xfs_buftarg_t *, unsigned int);
	393
	394	#define xfs_getsize_buftarg(buftarg) block_size((buftarg)->bt_bdev)
	395	#define xfs_readonly_buftarg(buftarg) bdev_read_only((buftarg)->bt_bdev)
	396
	397	#endif /* __XFS_BUF_H__ */