nfs: make it possible to disable nfs.mount-rmtab

When there are many NFS-clients doing very often mount/unmount actions,
the updating of the 'rmtab' can become a bottleneck and cause delays. In
these situations, the output of 'showmount' may be less important than
the responsiveness of the (un)mounting.

By setting 'nfs.mount-rmtab' to the value "/-", the cache file is not
updated anymore, and the entries are only kept in memory.

Cherry picked from commit 40407afb529f6e5fa2f79e9778c2f527122d75eb:
> Cherry picked from commit 331ef6e1a86bfc0a93f8a9dec6ad35c417873849:
>> BUG: 1169317
>> Change-Id: I40c4d8d754932f86fb2b1b2588843390464c773d
>> Reported-by: Cyril Peponnet <cyril@peponnet.fr>
>> Signed-off-by: Niels de Vos <ndevos@redhat.com>
>> Reviewed-on: http://review.gluster.org/9223
>> Tested-by: Gluster Build System <jenkins@build.gluster.com>
>> Reviewed-by: soumya k <skoduri@redhat.com>
>> Reviewed-by: jiffin tony Thottan <jthottan@redhat.com>
>> Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
>
> This change also contains the fixes to the test-case from:
>>
>> nfs: fix spurious failure in bug-1166862.t
>>
>> In some environments, "showmount" could return an NFS-client that does
>> not start with "1". This would cause the test-case to fail. The check is
>> incorrect, the number of lines should get counted instead.
>>
>> Also moving the test-case to the .../nfs/... subdirectory.
>>
>> Cherry picked from commit ee9b35a780607daddc2832b9af5ed6bf414aebc0:
>> BUG: 1166862
>> Change-Id: Ic03aa8145ca57d78aea01564466e924b03bb302a
>> Signed-off-by: Niels de Vos <ndevos@redhat.com>
>> Reviewed-on: http://review.gluster.org/10419
>> Tested-by: Gluster Build System <jenkins@build.gluster.com>
>> Reviewed-by: Vijay Bellur <vbellur@redhat.com>
>>
>
> Change-Id: I40c4d8d754932f86fb2b1b2588843390464c773d
> BUG: 1215385
> Signed-off-by: Niels de Vos <ndevos@redhat.com>
> Reviewed-on: http://review.gluster.org/10379
> Tested-by: NetBSD Build System
> Tested-by: Gluster Build System <jenkins@build.gluster.com>
> Reviewed-by: Vijay Bellur <vbellur@redhat.com>

Change-Id: I40c4d8d754932f86fb2b1b2588843390464c773d
BUG: 1234096
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/11335
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Raghavendra Bhat <raghavendra@redhat.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/xlators/nfs/server/src/nfs.c b/xlators/nfs/server/src/nfs.c
index c149119bf4d..e3258abf023 100644
--- a/xlators/nfs/server/src/nfs.c
+++ b/xlators/nfs/server/src/nfs.c
@@ -881,6 +881,12 @@ nfs_init_state (xlator_t *this)
                         gf_log (GF_NFS, GF_LOG_ERROR, "Failed to parse dict");
                         goto free_foppool;
                 }
+
+                /* check if writing the rmtab is disabled*/
+                if (nfs->rmtab && strcmp ("/-", nfs->rmtab) == 0) {
+                        GF_FREE (nfs->rmtab);
+                        nfs->rmtab = NULL;
+                }
         }
 
         /* support both options rpc-auth.ports.insecure and
@@ -1109,7 +1115,13 @@ nfs_reconfigure_state (xlator_t *this, dict_t *options)
                 }
                 gf_path_strip_trailing_slashes (rmtab);
         }
-        if (strcmp (nfs->rmtab, rmtab) != 0) {
+        /* check if writing the rmtab is disabled*/
+        if (strcmp ("/-", rmtab) == 0) {
+                GF_FREE (nfs->rmtab);
+                nfs->rmtab = NULL;
+                gf_log (GF_NFS, GF_LOG_INFO,
+                                "Disabled writing of nfs.mount-rmtab");
+        } else if (!nfs->rmtab || strcmp (nfs->rmtab, rmtab) != 0) {
                 mount_rewrite_rmtab (nfs->mstate, rmtab);
                 gf_log (GF_NFS, GF_LOG_INFO,
                                 "Reconfigured nfs.mount-rmtab path: %s",
@@ -1857,7 +1869,8 @@ struct volume_options options[] = {
                          "list all the NFS-clients that have connected "
                          "through the MOUNT protocol. If this is on shared "
                          "storage, all GlusterFS servers will update and "
-                         "output (with 'showmount') the same list."
+                         "output (with 'showmount') the same list. Set to "
+                         "\"/-\" to disable."
         },
         { .key = {OPT_SERVER_RPC_STATD},
           .type = GF_OPTION_TYPE_PATH,