xfs: unlock the inode before log force in xfs_fs_nfs_commit_metadata

Only read the LSN we need to push to with the ilock held, and then release
it before we do the log force to improve concurrency.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_export.c

@@ -229,16 +229,16 @@ xfs_fs_nfs_commit_metadata(
 {
 	struct xfs_inode	*ip = XFS_I(inode);
 	struct xfs_mount	*mp = ip->i_mount;
-	int			error = 0;
+	xfs_lsn_t		lsn = 0;
 
 	xfs_ilock(ip, XFS_ILOCK_SHARED);
-	if (xfs_ipincount(ip)) {
-		error = _xfs_log_force_lsn(mp, ip->i_itemp->ili_last_lsn,
-				XFS_LOG_SYNC, NULL);
-	}
+	if (xfs_ipincount(ip))
+		lsn = ip->i_itemp->ili_last_lsn;
 	xfs_iunlock(ip, XFS_ILOCK_SHARED);
 
-	return error;
+	if (!lsn)
+		return 0;
+	return _xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, NULL);
 }
 
 const struct export_operations xfs_export_operations = {