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authorChristoph Hellwig <hch@lst.de>2011-07-08 14:36:36 +0200
committerChristoph Hellwig <hch@lst.de>2011-07-08 14:36:36 +0200
commite163cbde981c5988c3e80ca29589132336f18a72 (patch)
tree735c72c28476969eddd4a39d878bb194f3609888 /fs/xfs
parent1d5ae5dfeee024d51fb2c0205035d7611a8f0c86 (diff)
downloadop-kernel-dev-e163cbde981c5988c3e80ca29589132336f18a72.zip
op-kernel-dev-e163cbde981c5988c3e80ca29589132336f18a72.tar.gz
xfs: avoid a few disk cache flushes
There is no need for a pre-flush when doing writing the second part of a split log buffer, and if we are using an external log there is no need to do a full cache flush of the log device at all given that all writes to it use the FUA flag. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Alex Elder <aelder@sgi.com> Reviewed-by: Dave Chinner <dchinner@redhat.com>
Diffstat (limited to 'fs/xfs')
-rw-r--r--fs/xfs/xfs_log.c18
1 files changed, 12 insertions, 6 deletions
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 4c2d30e..0ef5eb6 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1371,15 +1371,21 @@ xlog_sync(xlog_t *log,
bp->b_flags |= XBF_SYNCIO;
if (log->l_mp->m_flags & XFS_MOUNT_BARRIER) {
+ bp->b_flags |= XBF_FUA;
+
/*
- * If we have an external log device, flush the data device
- * before flushing the log to make sure all meta data
- * written back from the AIL actually made it to disk
- * before writing out the new log tail LSN in the log buffer.
+ * Flush the data device before flushing the log to make
+ * sure all meta data written back from the AIL actually made
+ * it to disk before stamping the new log tail LSN into the
+ * log buffer. For an external log we need to issue the
+ * flush explicitly, and unfortunately synchronously here;
+ * for an internal log we can simply use the block layer
+ * state machine for preflushes.
*/
if (log->l_mp->m_logdev_targp != log->l_mp->m_ddev_targp)
xfs_blkdev_issue_flush(log->l_mp->m_ddev_targp);
- bp->b_flags |= XBF_FUA | XBF_FLUSH;
+ else
+ bp->b_flags |= XBF_FLUSH;
}
ASSERT(XFS_BUF_ADDR(bp) <= log->l_logBBsize-1);
@@ -1414,7 +1420,7 @@ xlog_sync(xlog_t *log,
XFS_BUF_ASYNC(bp);
bp->b_flags |= XBF_SYNCIO;
if (log->l_mp->m_flags & XFS_MOUNT_BARRIER)
- bp->b_flags |= XBF_FUA | XBF_FLUSH;
+ bp->b_flags |= XBF_FUA;
dptr = XFS_BUF_PTR(bp);
/*
* Bump the cycle numbers at the start of each block
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