From 5adc94c247c3779782c7b0b8b5e28cf50596eb37 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Fri, 24 Sep 2010 21:58:31 +1000 Subject: [PATCH] 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 Reviewed-by: Christoph Hellwig Reviewed-by: Alex Elder --- fs/xfs/linux-2.6/xfs_buf.c | 34 ++++++++++++++++++++++++++++++++++ fs/xfs/linux-2.6/xfs_buf.h | 3 +++ 2 files changed, 37 insertions(+) diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c index eca945b0f88f..22c7bff77ad2 100644 --- a/fs/xfs/linux-2.6/xfs_buf.c +++ b/fs/xfs/linux-2.6/xfs_buf.c @@ -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, diff --git a/fs/xfs/linux-2.6/xfs_buf.h b/fs/xfs/linux-2.6/xfs_buf.h index fb30447091d8..57eedc750ee6 100644 --- a/fs/xfs/linux-2.6/xfs_buf.h +++ b/fs/xfs/linux-2.6/xfs_buf.h @@ -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 *);