xfs: optimise away log forces on timestamp updates for fdatasync

[deliverable/linux.git] / fs / xfs / xfs_file.c

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index e78feb400e22b22d59228b4f959d5b845848a675..c94699cbc667fd64954ca3ea2d2fe100e872a1c9 100644 (file)
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -242,19 +242,30 @@ xfs_file_fsync(
        }
 
        /*
-        * All metadata updates are logged, which means that we just have
-        * to flush the log up to the latest LSN that touched the inode.
+        * All metadata updates are logged, which means that we just have to
+        * flush the log up to the latest LSN that touched the inode. If we have
+        * concurrent fsync/fdatasync() calls, we need them to all block on the
+        * log force before we clear the ili_fsync_fields field. This ensures
+        * that we don't get a racing sync operation that does not wait for the
+        * metadata to hit the journal before returning. If we race with
+        * clearing the ili_fsync_fields, then all that will happen is the log
+        * force will do nothing as the lsn will already be on disk. We can't
+        * race with setting ili_fsync_fields because that is done under
+        * XFS_ILOCK_EXCL, and that can't happen because we hold the lock shared
+        * until after the ili_fsync_fields is cleared.
         */
        xfs_ilock(ip, XFS_ILOCK_SHARED);
        if (xfs_ipincount(ip)) {
                if (!datasync ||
-                   (ip->i_itemp->ili_fields & ~XFS_ILOG_TIMESTAMP))
+                   (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
                        lsn = ip->i_itemp->ili_last_lsn;
        }
-       xfs_iunlock(ip, XFS_ILOCK_SHARED);
 
-       if (lsn)
+       if (lsn) {
                error = _xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, &log_flushed);
+               ip->i_itemp->ili_fsync_fields = 0;
+       }
+       xfs_iunlock(ip, XFS_ILOCK_SHARED);
 
        /*
         * If we only have a single device, and the log force about was