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@xxxxxx>
Index: xfs/fs/xfs/linux-2.6/xfs_file.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_file.c 2011-06-09 11:50:25.239644994 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_file.c 2011-06-16 13:27:37.680255105 +0200
@@ -131,19 +131,34 @@ 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 the device used for file data
+ * first. This is to ensure newly written file data make
+ * it to disk before logging the new inode size in case of
+ * an extending write.
+ */
+ 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 +190,9 @@ 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 +224,25 @@ 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);
- }
+ /*
+ * If we only have a single device, and the log force about was
+ * a no-op we might have to flush the data device cache here.
+ * This can only happen for fdatasync/O_DSYNC if we were overwriting
+ * an already allocated file and thus do not have any metadata to
+ * commit.
+ */
+ 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 2011-06-16 13:10:42.240306517 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_super.c 2011-06-16 13:11:53.650302901 +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)
@@ -1240,14 +1178,6 @@ 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;
@@ -1282,8 +1212,6 @@ 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
@@ -1465,9 +1393,6 @@ 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 2011-06-09 11:50:25.266311660 +0200
+++ xfs/fs/xfs/xfs_log.c 2011-06-16 13:25:08.210262674 +0200
@@ -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);
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