glusterd, readdir-ahead: Fix backward incompatibility

Backport of https://review.gluster.org/#/c/16657/

Issue:
Any opion is spcified in two places: In the options[] of xlator
itself and glusterd-volume-set.c. The default value of this option
can be specified in both the places. If its specified only in xlator
then the volfile generated will not have the option and default value,
it will be assigned during graph initialization.
With patch [1] the option rda-request-size was changed from INT to SIZET
type, and default was changed from 131072 to 128KB, but was specified
only in the readdir-ahead.c. Thus with this patch alone the volfile
entry for readdir-ahead looks like:
volume patchy-readdir-ahead
    type performance/readdir-ahead
    subvolumes patchy-read-ahead
end-volume

With patch [2], the default of option rda-request-size was specified
in glusterd-volume-set.c as well(as it was necessary fr parallel readdir).
With this patch the readdir entry in the volfile will look like:
volume patchy-readdir-ahead
    type performance/readdir-ahead
    option rda-cache-limit 10MB
    option rda-request-size 128KB
    option parallel-readdir off
    subvolumes patchy-read-ahead
end-volume


Now consider the server has both these patches and client doesn't.
Server will generate a volfile with entry:

The old clients which thought the option rda-request-size is of type
INT will now recieve the value 128KB which it willn't understand,
and hence fail the mount.

The issue is seen only with the combination of [1] and [2].

Solution:
Instead of specifying 128KB as default in glusterd we specify 131072
so that the old clients will interpret as INT and new ones as 128KB

Credits: Raghavendra G

> Reviewed-on: https://review.gluster.org/16657
> Smoke: Gluster Build System <jenkins@build.gluster.org>
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>
> Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
> Reviewed-by: Atin Mukherjee <amukherj@redhat.com>

Change-Id: I0c269a5890957fd8a38e9a05bdec088645a6688a
BUG: 1423412
Signed-off-by: Poornima G <pgurusid@redhat.com>
Reviewed-on: https://review.gluster.org/16658
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Atin Mukherjee <amukherj@redhat.com>

2 files changed, 2 insertions, 2 deletions

diff --git a/xlators/mgmt/glusterd/src/glusterd-volume-set.c b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
index 6ab4f7cc550..aca7135a2b2 100644
--- a/xlators/mgmt/glusterd/src/glusterd-volume-set.c
+++ b/xlators/mgmt/glusterd/src/glusterd-volume-set.c
@@ -3098,7 +3098,7 @@ struct volopt_map_entry glusterd_volopt_map[] = {
 	{ .key         = "performance.rda-request-size",
 	  .voltype     = "performance/readdir-ahead",
           .option      = "rda-request-size",
-          .value       = "128KB",
+          .value       = "131072",
           .flags       = OPT_FLAG_CLIENT_OPT,
           .type        = DOC,
           .op_version  = GD_OP_VERSION_3_9_1,
diff --git a/xlators/performance/readdir-ahead/src/readdir-ahead.c b/xlators/performance/readdir-ahead/src/readdir-ahead.c
index c6b167725a5..9b0870e2b37 100644
--- a/xlators/performance/readdir-ahead/src/readdir-ahead.c
+++ b/xlators/performance/readdir-ahead/src/readdir-ahead.c
@@ -726,7 +726,7 @@ struct volume_options options[] = {
 	  .type = GF_OPTION_TYPE_SIZET,
 	  .min = 4096,
 	  .max = 131072,
-	  .default_value = "128KB",
+	  .default_value = "131072",
 	  .description = "size of buffer in readdirp calls initiated by "
                          "readdir-ahead ",
 	},