arbiter: write performance improvement

Problem: The throughput for a 'dd' workload was much less for arbiter
configuration when compared to normal replica-3 volume. There were 2
issues:

i)arbiter_writev was using the request dict as response dict while
unwinding, leading to incorect GLUSTERFS_WRITE_IS_APPEND and
GLUSTERFS_OPEN_FD_COUNT values (=4), leading to immediate post-ops
because is_afr_delayed_changelog_post_op_needed() failed due to
afr_are_multiple_fds_opened() check.

ii) The arbiter code in afr was setting local->transaction.{start and len} =0
to take full file locks. What this meant was even for simultaenous but
non-overlapping writevs, afr_transaction_eager_lock_init() was not
happening because afr_locals_overlap() always stays true. Consequently
is_afr_delayed_changelog_post_op_needed() failed due to
local->delayed_post_op not being set.

Fix:
i) Send appropriate response dict values in arbiter_writev.
ii) Modify flock params instead of local->transaction.{start and len} to
take full file locks in the transaction.

Also changed _fill_writev_xdata() in posix to fill rsp_xdata for
whatever key is requested for.

Change-Id: I1c5fc5e98aba49ade540bb441a022e65b753432a
BUG: 1324004
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reported-by: Robert Rauch <robert.rauch@gns-systems.de>
Reported-by: Russel Purinton <russell.purinton@gmail.com>
Reviewed-on: http://review.gluster.org/13906
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Smoke: Gluster Build System <jenkins@build.gluster.com>
CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>

1 files changed, 21 insertions, 14 deletions

diff --git a/xlators/storage/posix/src/posix.c b/xlators/storage/posix/src/posix.c
index f72c13d9066..8cce4be1c34 100644
--- a/xlators/storage/posix/src/posix.c
+++ b/xlators/storage/posix/src/posix.c
@@ -3055,28 +3055,35 @@ _fill_writev_xdata (fd_t *fd, dict_t *xdata, xlator_t *this, int is_append)
                 goto out;
         }
 
-        if (!xdata || !dict_get (xdata, GLUSTERFS_OPEN_FD_COUNT))
+        if (!xdata)
                 goto out;
 
         rsp_xdata = dict_new();
         if (!rsp_xdata)
                 goto out;
 
-        ret = dict_set_uint32 (rsp_xdata, GLUSTERFS_OPEN_FD_COUNT,
-                               fd->inode->fd_count);
-        if (ret < 0) {
-                gf_msg (this->name, GF_LOG_WARNING, 0, P_MSG_DICT_SET_FAILED,
-                        "%s: Failed to set dictionary value for %s",
-                        uuid_utoa (fd->inode->gfid), GLUSTERFS_OPEN_FD_COUNT);
+        if (dict_get (xdata, GLUSTERFS_OPEN_FD_COUNT)) {
+                ret = dict_set_uint32 (rsp_xdata, GLUSTERFS_OPEN_FD_COUNT,
+                                       fd->inode->fd_count);
+                if (ret < 0) {
+                        gf_msg (this->name, GF_LOG_WARNING, 0,
+                                P_MSG_DICT_SET_FAILED, "%s: Failed to set "
+                                "dictionary value for %s",
+                                uuid_utoa (fd->inode->gfid),
+                                GLUSTERFS_OPEN_FD_COUNT);
+                }
         }
 
-        ret = dict_set_uint32 (rsp_xdata, GLUSTERFS_WRITE_IS_APPEND,
-                               is_append);
-        if (ret < 0) {
-                gf_msg (this->name, GF_LOG_WARNING, 0, P_MSG_DICT_SET_FAILED,
-                        "%s: Failed to set dictionary value for %s",
-                        uuid_utoa (fd->inode->gfid),
-                        GLUSTERFS_WRITE_IS_APPEND);
+        if (dict_get (xdata, GLUSTERFS_WRITE_IS_APPEND)) {
+                ret = dict_set_uint32 (rsp_xdata, GLUSTERFS_WRITE_IS_APPEND,
+                                       is_append);
+                if (ret < 0) {
+                        gf_msg (this->name, GF_LOG_WARNING, 0,
+                                P_MSG_DICT_SET_FAILED, "%s: Failed to set "
+                                "dictionary value for %s",
+                                uuid_utoa (fd->inode->gfid),
+                                GLUSTERFS_WRITE_IS_APPEND);
+                }
         }
 out:
         return rsp_xdata;