geo-rep / gsyncd: fix cleanup of temporary mounts

[This is a "forward port" of fafd5c17, http://review.gluster.com/2908]

The "finally" clause that was meant to cleanup after the
temp mount has not covered the case of getting signalled
(eg. by monitor, upon worker timing out).

So here we "outsource" the cleanup to an ephemeral child process.
Child calls setsid(2) so it won't be bothered by internal process
management. We use a pipe in between worker and the cleanup child;
when child sees the worker end getting closed, it performs the cleanup.
Worker end can get closed either because worker closes it (normal case),
or because worker has terminated (faulty case) -- thus as bonus, we get
a nice uniform handling with no need to differentiate between normal and
faulty cases.

The faulty case that was seen IRL -- ie., users of maintainance mounts
hang in chdir(2) to mount point -- can be simulated for testing purposes
by applying the following patch:

  diff --git a/xlators/mount/fuse/src/fuse-bridge.c b/xlators/mount/fuse/src/fuse-bridge.c
  index acd3c68..1ce5dc1 100644
  --- a/xlators/mount/fuse/src/fuse-bridge.c
  +++ b/xlators/mount/fuse/src/fuse-bridge.c
  @@ -2918,7 +2918,7 @@ fuse_init (xlator_t *this, fuse_in_header_t *finh, void *msg)
           if (fini->minor < 9)
                   *priv->msg0_len_p = sizeof(*finh) + FUSE_COMPAT_WRITE_IN_SIZE;
   #endif
  -        ret = send_fuse_obj (this, finh, &fino);
  +        ret = priv->client_pid_set ? 0 : send_fuse_obj (this, finh, &fino);
           if (ret == 0)
                   gf_log ("glusterfs-fuse", GF_LOG_INFO,
                           "FUSE inited with protocol versions:"

Change-Id: I14bad56a60a7fa82d0104fa4b9a20f4e42a7186f
BUG: 786291
Signed-off-by: Csaba Henk <csaba@redhat.com>
Reviewed-on: http://review.gluster.com/3259
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-by: Anand Avati <avati@redhat.com>

0 files changed, 0 insertions, 0 deletions