cluster/tier: readdirp to cold tier only

It is possible a file would get migrated in the middle
of a readdir operation. If there are four subvolumes A,B,C,D,
and if readdir reads them in order and reaches subvol B,
then, if a file is moved from D to A, it will not be included
in the readdir output.

This phenonema has pre-existed in DHT migration but is more
apparent in tiering.

When a file is moved off the hashed subvolume a T file is created.
For tiering, we will make the cold subvolume the hashed subvolume.
This will ensure the creation of a T file. Readdir will not skip T
files in the tier translator.

Making the cold subvolume the hashed subvolume ensures the T
files created on promotions or creates will be less likely to
fill the volume.

Creates still put the data on the hot subvolume.

Change-Id: Ifde557d3d0e94a4570ca9f115adee3db2ee75407
BUG:  1281598
Signed-off-by: Dan Lambright <dlambrig@redhat.com>
Reviewed-on: http://review.gluster.org/12530
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Reviewed-by: N Balachandran <nbalacha@redhat.com>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/xlators/cluster/dht/src/tier-common.h b/xlators/cluster/dht/src/tier-common.h
new file mode 100644
index 00000000000..93a71f75252
--- /dev/null
+++ b/xlators/cluster/dht/src/tier-common.h
@@ -0,0 +1,26 @@
+/*
+  Copyright (c) 2015 Red Hat, Inc. <http://www.redhat.com>
+  This file is part of GlusterFS.
+
+  This file is licensed to you under your choice of the GNU Lesser
+  General Public License, version 3 or any later version (LGPLv3 or
+  later), or the GNU General Public License, version 2 (GPLv2), in all
+  cases as published by the Free Software Foundation.
+*/
+
+#ifndef _TIER_COMMON_H_
+#define _TIER_COMMON_H_
+
+int32_t
+tier_readdirp (call_frame_t *frame,
+               xlator_t *this,
+               fd_t     *fd,
+               size_t    size, off_t off, dict_t *dict);
+
+int
+tier_readdir (call_frame_t *frame,
+              xlator_t *this, fd_t *fd, size_t size,
+              off_t yoff, dict_t *xdata);
+
+#endif
+