[PATCH] xfs: make log devices with write back caches work
Christoph Hellwig
hch at infradead.org
Fri May 27 11:41:37 CDT 2011
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 at lst.de>
Index: xfs/fs/xfs/linux-2.6/xfs_file.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_file.c 2011-05-27 13:07:41.260498122 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_file.c 2011-05-27 17:37:30.152495811 +0200
@@ -131,19 +131,32 @@ xfs_file_fsync(
{
struct inode *inode = file->f_mapping->host;
struct xfs_inode *ip = XFS_I(inode);
+ struct xfs_mount *mp = ip->i_mount;
struct xfs_trans *tp;
int error = 0;
int log_flushed = 0;
trace_xfs_file_fsync(ip);
- if (XFS_FORCED_SHUTDOWN(ip->i_mount))
+ if (XFS_FORCED_SHUTDOWN(mp))
return -XFS_ERROR(EIO);
xfs_iflags_clear(ip, XFS_ITRUNCATED);
xfs_ioend_wait(ip);
+ if (mp->m_flags & XFS_MOUNT_BARRIER) {
+ /*
+ * If we have an RT and/or log subvolume we need to make sure
+ * to flush the write cache on the device that the data
+ * resides before commit the transaction.
+ */
+ if (XFS_IS_REALTIME_INODE(ip))
+ xfs_blkdev_issue_flush(mp->m_rtdev_targp);
+ else if (mp->m_logdev_targp != mp->m_ddev_targp)
+ xfs_blkdev_issue_flush(mp->m_ddev_targp);
+ }
+
/*
* We always need to make sure that the required inode state is safe on
* disk. The inode might be clean but we still might need to force the
@@ -175,9 +188,9 @@ xfs_file_fsync(
* updates. The sync transaction will also force the log.
*/
xfs_iunlock(ip, XFS_ILOCK_SHARED);
- tp = xfs_trans_alloc(ip->i_mount, XFS_TRANS_FSYNC_TS);
+ tp = xfs_trans_alloc(mp, XFS_TRANS_FSYNC_TS);
error = xfs_trans_reserve(tp, 0,
- XFS_FSYNC_TS_LOG_RES(ip->i_mount), 0, 0, 0);
+ XFS_FSYNC_TS_LOG_RES(mp), 0, 0, 0);
if (error) {
xfs_trans_cancel(tp, 0);
return -error;
@@ -209,28 +222,23 @@ xfs_file_fsync(
* force the log.
*/
if (xfs_ipincount(ip)) {
- error = _xfs_log_force_lsn(ip->i_mount,
+ error = _xfs_log_force_lsn(mp,
ip->i_itemp->ili_last_lsn,
XFS_LOG_SYNC, &log_flushed);
}
xfs_iunlock(ip, XFS_ILOCK_SHARED);
}
- if (ip->i_mount->m_flags & XFS_MOUNT_BARRIER) {
- /*
- * If the log write didn't issue an ordered tag we need
- * to flush the disk cache for the data device now.
- */
- if (!log_flushed)
- xfs_blkdev_issue_flush(ip->i_mount->m_ddev_targp);
-
- /*
- * If this inode is on the RT dev we need to flush that
- * cache as well.
- */
- if (XFS_IS_REALTIME_INODE(ip))
- xfs_blkdev_issue_flush(ip->i_mount->m_rtdev_targp);
- }
+ /*
+ * Flush the write cache on the data volume, if the data for this
+ * inode actually resides on it, and the transaction commit did
+ * not flush it yet.
+ */
+ if ((mp->m_flags & XFS_MOUNT_BARRIER) &&
+ mp->m_logdev_targp == mp->m_ddev_targp &&
+ !XFS_IS_REALTIME_INODE(ip) &&
+ !log_flushed)
+ xfs_blkdev_issue_flush(mp->m_ddev_targp);
return -error;
}
Index: xfs/fs/xfs/linux-2.6/xfs_super.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_super.c 2011-05-27 13:07:41.272495356 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_super.c 2011-05-27 15:37:11.673496345 +0200
@@ -627,68 +627,6 @@ xfs_blkdev_put(
blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
}
-/*
- * Try to write out the superblock using barriers.
- */
-STATIC int
-xfs_barrier_test(
- xfs_mount_t *mp)
-{
- xfs_buf_t *sbp = xfs_getsb(mp, 0);
- int error;
-
- XFS_BUF_UNDONE(sbp);
- XFS_BUF_UNREAD(sbp);
- XFS_BUF_UNDELAYWRITE(sbp);
- XFS_BUF_WRITE(sbp);
- XFS_BUF_UNASYNC(sbp);
- XFS_BUF_ORDERED(sbp);
-
- xfsbdstrat(mp, sbp);
- error = xfs_buf_iowait(sbp);
-
- /*
- * Clear all the flags we set and possible error state in the
- * buffer. We only did the write to try out whether barriers
- * worked and shouldn't leave any traces in the superblock
- * buffer.
- */
- XFS_BUF_DONE(sbp);
- XFS_BUF_ERROR(sbp, 0);
- XFS_BUF_UNORDERED(sbp);
-
- xfs_buf_relse(sbp);
- return error;
-}
-
-STATIC void
-xfs_mountfs_check_barriers(xfs_mount_t *mp)
-{
- int error;
-
- if (mp->m_logdev_targp != mp->m_ddev_targp) {
- xfs_notice(mp,
- "Disabling barriers, not supported with external log device");
- mp->m_flags &= ~XFS_MOUNT_BARRIER;
- return;
- }
-
- if (xfs_readonly_buftarg(mp->m_ddev_targp)) {
- xfs_notice(mp,
- "Disabling barriers, underlying device is readonly");
- mp->m_flags &= ~XFS_MOUNT_BARRIER;
- return;
- }
-
- error = xfs_barrier_test(mp);
- if (error) {
- xfs_notice(mp,
- "Disabling barriers, trial barrier write failed");
- mp->m_flags &= ~XFS_MOUNT_BARRIER;
- return;
- }
-}
-
void
xfs_blkdev_issue_flush(
xfs_buftarg_t *buftarg)
@@ -1239,14 +1177,6 @@ xfs_fs_remount(
switch (token) {
case Opt_barrier:
mp->m_flags |= XFS_MOUNT_BARRIER;
-
- /*
- * Test if barriers are actually working if we can,
- * else delay this check until the filesystem is
- * marked writeable.
- */
- if (!(mp->m_flags & XFS_MOUNT_RDONLY))
- xfs_mountfs_check_barriers(mp);
break;
case Opt_nobarrier:
mp->m_flags &= ~XFS_MOUNT_BARRIER;
@@ -1281,8 +1211,6 @@ xfs_fs_remount(
/* ro -> rw */
if ((mp->m_flags & XFS_MOUNT_RDONLY) && !(*flags & MS_RDONLY)) {
mp->m_flags &= ~XFS_MOUNT_RDONLY;
- if (mp->m_flags & XFS_MOUNT_BARRIER)
- xfs_mountfs_check_barriers(mp);
/*
* If this is the first remount to writeable state we
@@ -1464,9 +1392,6 @@ xfs_fs_fill_super(
if (error)
goto out_free_sb;
- if (mp->m_flags & XFS_MOUNT_BARRIER)
- xfs_mountfs_check_barriers(mp);
-
error = xfs_filestream_mount(mp);
if (error)
goto out_free_sb;
Index: xfs/fs/xfs/xfs_log.c
===================================================================
--- xfs.orig/fs/xfs/xfs_log.c 2011-05-27 13:07:41.284496076 +0200
+++ xfs/fs/xfs/xfs_log.c 2011-05-27 15:37:11.681500020 +0200
@@ -1372,8 +1372,15 @@ 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.
+ */
+ 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);
More information about the xfs
mailing list