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xfs: make log devices with write back caches work

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There's no reason not to support cache flushing on external log devices.
The only thing this really requires is flushing the data device first
both in fsync and log commits.  A side effect is that we also have to
remove the barrier write test during mount, which has been superflous
since the new FLUSH+FUA code anyway.  Also use the chance to flush the
RT subvolume write cache before the fsync commit, which is required
for correct semantics.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
This commit is contained in:
Christoph Hellwig
2011-06-16 12:02:23 +00:00
committed by Alex Elder
parent c46a131c0c
commit a27a263bae
3 changed files with 41 additions and 95 deletions
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11
fs/xfs/xfs_log.c
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@@ -1372,8 +1372,17 @@ xlog_sync(xlog_t *log,
XFS_BUF_ASYNC(bp);
bp->b_flags |= XBF_LOG_BUFFER;
if (log->l_mp->m_flags & XFS_MOUNT_BARRIER)
if (log->l_mp->m_flags & XFS_MOUNT_BARRIER) {
/*
* 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.
*/
if (log->l_mp->m_logdev_targp != log->l_mp->m_ddev_targp)
xfs_blkdev_issue_flush(log->l_mp->m_ddev_targp);
XFS_BUF_ORDERED(bp);
}
ASSERT(XFS_BUF_ADDR(bp) <= log->l_logBBsize-1);
ASSERT(XFS_BUF_ADDR(bp) + BTOBB(count) <= log->l_logBBsize);