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Commit 5adc94c2 authored by Dave Chinner's avatar Dave Chinner Committed by Alex Elder
Browse files

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: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarAlex Elder <aelder@sgi.com>
parent 686865f7

fs/xfs/linux-2.6/xfs_buf.c

+34 −0
Original line number Diff line number Diff line
@@ -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,

fs/xfs/linux-2.6/xfs_buf.h

+3 −0
Original line number Diff line number Diff line
@@ -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 *);