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xfs: introduced uncached buffer read primitve 

To avoid the need to use cached buffers for single-shot or buffers
cached at the filesystem level, introduce a new buffer read
primitive that bypasses the cache an reads directly from disk.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
This commit is contained in:
Dave Chinner 2010-09-24 21:58:31 +10:00 committed by Alex Elder
parent 686865f76e
commit 5adc94c247
2 changed files with 37 additions and 0 deletions
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34
fs/xfs/linux-2.6/xfs_buf.c
View File

@ -638,6 +638,40 @@ xfs_buf_readahead(
xfs_buf_read(target, ioff, isize, flags);
}
/*
* Read an uncached buffer from disk. Allocates and returns a locked
* buffer containing the disk contents or nothing.
*/
struct xfs_buf *
xfs_buf_read_uncached(
struct xfs_mount *mp,
struct xfs_buftarg *target,
xfs_daddr_t daddr,
size_t length,
int flags)
{
xfs_buf_t *bp;
int error;
bp = xfs_buf_get_uncached(target, length, flags);
if (!bp)
return NULL;
/* set up the buffer for a read IO */
xfs_buf_lock(bp);
XFS_BUF_SET_ADDR(bp, daddr);
XFS_BUF_READ(bp);
XFS_BUF_BUSY(bp);
xfsbdstrat(mp, bp);
error = xfs_iowait(bp);
if (error || bp->b_error) {
xfs_buf_relse(bp);
return NULL;
}
return bp;
}
xfs_buf_t *
xfs_buf_get_empty(
size_t len,

3
fs/xfs/linux-2.6/xfs_buf.h
View File

@ -218,6 +218,9 @@ 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,
xfs_buf_flags_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 *);