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alistair23-linux/fs/xfs/linux-2.6/xfs_buf.h
Dave Chinner 0e6e847ffe xfs: stop using the page cache to back the buffer cache 
Now that the buffer cache has it's own LRU, we do not need to use
the page cache to provide persistent caching and reclaim
infrastructure. Convert the buffer cache to use alloc_pages()
instead of the page cache. This will remove all the overhead of page
cache management from setup and teardown of the buffers, as well as
needing to mark pages accessed as we find buffers in the buffer
cache.

By avoiding the page cache, we also remove the need to keep state in
the page_private(page) field for persistant storage across buffer
free/buffer rebuild and so all that code can be removed. This also
fixes the long-standing problem of not having enough bits in the
page_private field to track all the state needed for a 512
sector/64k page setup.

It also removes the need for page locking during reads as the pages
are unique to the buffer and nobody else will be attempting to
access them.

Finally, it removes the buftarg address space lock as a point of
global contention on workloads that allocate and free buffers
quickly such as when creating or removing large numbers of inodes in
parallel. This remove the 16TB limit on filesystem size on 32 bit
machines as the page index (32 bit) is no longer used for lookups
of metadata buffers - the buffer cache is now solely indexed by disk
address which is stored in a 64 bit field in the buffer.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>
2011-03-26 09:16:45 +11:00

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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 <asm/system.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))
#define xfs_buf_ctob(pp) ((pp) * PAGE_CACHE_SIZE)
#define xfs_buf_btoc(dd) (((dd) + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT)
#define xfs_buf_btoct(dd) ((dd) >> PAGE_CACHE_SHIFT)
#define xfs_buf_poff(aa) ((aa) & ~PAGE_CACHE_MASK)
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_MAPPED (1 << 2) /* buffer mapped (b_addr valid) */
#define XBF_ASYNC (1 << 4) /* initiator will not wait for completion */
#define XBF_DONE (1 << 5) /* all pages in the buffer uptodate */
#define XBF_DELWRI (1 << 6) /* buffer has dirty pages */
#define XBF_STALE (1 << 7) /* buffer has been staled, do not find it */
#define XBF_ORDERED (1 << 11)/* use ordered writes */
#define XBF_READ_AHEAD (1 << 12)/* asynchronous read-ahead */
#define XBF_LOG_BUFFER (1 << 13)/* this is a buffer used for the log */
/* flags used only as arguments to access routines */
#define XBF_LOCK (1 << 14)/* lock requested */
#define XBF_TRYLOCK (1 << 15)/* lock requested, but do not wait */
#define XBF_DONT_BLOCK (1 << 16)/* do not block in current thread */
/* flags used only internally */
#define _XBF_PAGES (1 << 18)/* backed by refcounted pages */
#define _XBF_RUN_QUEUES (1 << 19)/* run block device task queue */
#define _XBF_KMEM (1 << 20)/* backed by heap memory */
#define _XBF_DELWRI_Q (1 << 21)/* buffer on delwri queue */
typedef unsigned int xfs_buf_flags_t;
#define XFS_BUF_FLAGS \
{ XBF_READ, "READ" }, \
{ XBF_WRITE, "WRITE" }, \
{ XBF_MAPPED, "MAPPED" }, \
{ XBF_ASYNC, "ASYNC" }, \
{ XBF_DONE, "DONE" }, \
{ XBF_DELWRI, "DELWRI" }, \
{ XBF_STALE, "STALE" }, \
{ XBF_ORDERED, "ORDERED" }, \
{ XBF_READ_AHEAD, "READ_AHEAD" }, \
{ XBF_LOCK, "LOCK" }, /* should never be set */\
{ XBF_TRYLOCK, "TRYLOCK" }, /* ditto */\
{ XBF_DONT_BLOCK, "DONT_BLOCK" }, /* ditto */\
{ _XBF_PAGES, "PAGES" }, \
{ _XBF_RUN_QUEUES, "RUN_QUEUES" }, \
{ _XBF_KMEM, "KMEM" }, \
{ _XBF_DELWRI_Q, "DELWRI_Q" }
typedef enum {
XBT_FORCE_SLEEP = 0,
XBT_FORCE_FLUSH = 1,
} xfs_buftarg_flags_t;
typedef struct xfs_bufhash {
struct list_head bh_list;
spinlock_t bh_lock;
} xfs_bufhash_t;
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;
/* per device delwri queue */
struct task_struct *bt_task;
struct list_head bt_delwrite_queue;
spinlock_t bt_delwrite_lock;
unsigned long bt_flags;
/* 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
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_off_t b_file_offset; /* offset in file */
size_t b_buffer_length;/* size of buffer in bytes */
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 */
struct list_head b_lru; /* lru list */
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) */
xfs_daddr_t b_bn; /* block number for I/O */
size_t b_count_desired;/* desired transfer size */
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;
void *b_fspriv2;
struct page **b_pages; /* array of page pointers */
struct page *b_page_array[XB_PAGES]; /* inline pages */
unsigned long b_queuetime; /* time buffer was queued */
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 */
extern xfs_buf_t *_xfs_buf_find(xfs_buftarg_t *, xfs_off_t, size_t,
xfs_buf_flags_t, xfs_buf_t *);
#define xfs_incore(buftarg,blkno,len,lockit) \
_xfs_buf_find(buftarg, blkno ,len, lockit, NULL)
extern xfs_buf_t *xfs_buf_get(xfs_buftarg_t *, xfs_off_t, size_t,
xfs_buf_flags_t);
extern xfs_buf_t *xfs_buf_read(xfs_buftarg_t *, xfs_off_t, size_t,
xfs_buf_flags_t);
extern xfs_buf_t *xfs_buf_get_empty(size_t, xfs_buftarg_t *);
extern xfs_buf_t *xfs_buf_get_uncached(struct xfs_buftarg *, size_t, int);
extern int xfs_buf_associate_memory(xfs_buf_t *, void *, size_t);
extern void xfs_buf_hold(xfs_buf_t *);
extern void xfs_buf_readahead(xfs_buftarg_t *, xfs_off_t, size_t);
struct xfs_buf *xfs_buf_read_uncached(struct xfs_mount *mp,
struct xfs_buftarg *target,
xfs_daddr_t daddr, size_t length, int flags);
/* 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_cond_lock(xfs_buf_t *);
extern int xfs_buf_lock_value(xfs_buf_t *);
extern void xfs_buf_lock(xfs_buf_t *);
extern void xfs_buf_unlock(xfs_buf_t *);
/* Buffer Read and Write Routines */
extern int xfs_bwrite(struct xfs_mount *mp, struct xfs_buf *bp);
extern void xfs_bdwrite(void *mp, xfs_buf_t *bp);
extern void xfsbdstrat(struct xfs_mount *, struct xfs_buf *);
extern int xfs_bdstrat_cb(struct xfs_buf *);
extern void xfs_buf_ioend(xfs_buf_t *, int);
extern void xfs_buf_ioerror(xfs_buf_t *, int);
extern int 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 void xfs_buf_delwri_dequeue(xfs_buf_t *);
extern void xfs_buf_delwri_promote(xfs_buf_t *);
/* Buffer Daemon Setup Routines */
extern int xfs_buf_init(void);
extern void xfs_buf_terminate(void);
#define xfs_buf_target_name(target) \
({ char __b[BDEVNAME_SIZE]; bdevname((target)->bt_bdev, __b); __b; })
#define XFS_BUF_BFLAGS(bp) ((bp)->b_flags)
#define XFS_BUF_ZEROFLAGS(bp) ((bp)->b_flags &= \
~(XBF_READ|XBF_WRITE|XBF_ASYNC|XBF_DELWRI|XBF_ORDERED))
void xfs_buf_stale(struct xfs_buf *bp);
#define XFS_BUF_STALE(bp) xfs_buf_stale(bp);
#define XFS_BUF_UNSTALE(bp) ((bp)->b_flags &= ~XBF_STALE)
#define XFS_BUF_ISSTALE(bp) ((bp)->b_flags & XBF_STALE)
#define XFS_BUF_SUPER_STALE(bp) do { \
XFS_BUF_STALE(bp); \
xfs_buf_delwri_dequeue(bp); \
XFS_BUF_DONE(bp); \
} while (0)
#define XFS_BUF_DELAYWRITE(bp) ((bp)->b_flags |= XBF_DELWRI)
#define XFS_BUF_UNDELAYWRITE(bp) xfs_buf_delwri_dequeue(bp)
#define XFS_BUF_ISDELAYWRITE(bp) ((bp)->b_flags & XBF_DELWRI)
#define XFS_BUF_ERROR(bp,no) xfs_buf_ioerror(bp,no)
#define XFS_BUF_GETERROR(bp) xfs_buf_geterror(bp)
#define XFS_BUF_ISERROR(bp) (xfs_buf_geterror(bp) ? 1 : 0)
#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_BUSY(bp) do { } while (0)
#define XFS_BUF_UNBUSY(bp) do { } while (0)
#define XFS_BUF_ISBUSY(bp) (1)
#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_ORDERED(bp) ((bp)->b_flags |= XBF_ORDERED)
#define XFS_BUF_UNORDERED(bp) ((bp)->b_flags &= ~XBF_ORDERED)
#define XFS_BUF_ISORDERED(bp) ((bp)->b_flags & XBF_ORDERED)
#define XFS_BUF_HOLD(bp) xfs_buf_hold(bp)
#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)
#define XFS_BUF_IODONE_FUNC(bp) ((bp)->b_iodone)
#define XFS_BUF_SET_IODONE_FUNC(bp, func) ((bp)->b_iodone = (func))
#define XFS_BUF_CLR_IODONE_FUNC(bp) ((bp)->b_iodone = NULL)
#define XFS_BUF_FSPRIVATE(bp, type) ((type)(bp)->b_fspriv)
#define XFS_BUF_SET_FSPRIVATE(bp, val) ((bp)->b_fspriv = (void*)(val))
#define XFS_BUF_FSPRIVATE2(bp, type) ((type)(bp)->b_fspriv2)
#define XFS_BUF_SET_FSPRIVATE2(bp, val) ((bp)->b_fspriv2 = (void*)(val))
#define XFS_BUF_SET_START(bp) do { } while (0)
#define XFS_BUF_PTR(bp) (xfs_caddr_t)((bp)->b_addr)
#define XFS_BUF_SET_PTR(bp, val, cnt) xfs_buf_associate_memory(bp, val, cnt)
#define XFS_BUF_ADDR(bp) ((bp)->b_bn)
#define XFS_BUF_SET_ADDR(bp, bno) ((bp)->b_bn = (xfs_daddr_t)(bno))
#define XFS_BUF_OFFSET(bp) ((bp)->b_file_offset)
#define XFS_BUF_SET_OFFSET(bp, off) ((bp)->b_file_offset = (off))
#define XFS_BUF_COUNT(bp) ((bp)->b_count_desired)
#define XFS_BUF_SET_COUNT(bp, cnt) ((bp)->b_count_desired = (cnt))
#define XFS_BUF_SIZE(bp) ((bp)->b_buffer_length)
#define XFS_BUF_SET_SIZE(bp, cnt) ((bp)->b_buffer_length = (cnt))
static inline void
xfs_buf_set_ref(
struct xfs_buf *bp,
int lru_ref)
{
atomic_set(&bp->b_lru_ref, lru_ref);
}
#define XFS_BUF_SET_VTYPE_REF(bp, type, ref) xfs_buf_set_ref(bp, ref)
#define XFS_BUF_SET_VTYPE(bp, type) do { } while (0)
#define XFS_BUF_ISPINNED(bp) atomic_read(&((bp)->b_pin_count))
#define XFS_BUF_VALUSEMA(bp) xfs_buf_lock_value(bp)
#define XFS_BUF_CPSEMA(bp) (xfs_buf_cond_lock(bp) == 0)
#define XFS_BUF_VSEMA(bp) xfs_buf_unlock(bp)
#define XFS_BUF_PSEMA(bp,x) xfs_buf_lock(bp)
#define XFS_BUF_FINISH_IOWAIT(bp) complete(&bp->b_iowait);
#define XFS_BUF_SET_TARGET(bp, target) ((bp)->b_target = (target))
#define XFS_BUF_TARGET(bp) ((bp)->b_target)
#define XFS_BUFTARG_NAME(target) xfs_buf_target_name(target)
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);
extern int xfs_flush_buftarg(xfs_buftarg_t *, int);
#ifdef CONFIG_KDB_MODULES
extern struct list_head *xfs_get_buftarg_list(void);
#endif
#define xfs_getsize_buftarg(buftarg) block_size((buftarg)->bt_bdev)
#define xfs_readonly_buftarg(buftarg) bdev_read_only((buftarg)->bt_bdev)
#define xfs_binval(buftarg) xfs_flush_buftarg(buftarg, 1)
#define XFS_bflush(buftarg) xfs_flush_buftarg(buftarg, 1)
#endif /* __XFS_BUF_H__ */
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