libgfchangelog: Fix faulty reference to xlator context

Problem:
libgfchangelog initializes global xlator on library load (via
constructor: _ctor) and mangles it's xlator context thereby
messing with certain important members of the command structure.
On receiving an RPC disconnection event, if the point-of-execution
was in libgfchangelogs context, accessing ->cmd_args during RPC
notify resulted in a segfault.

Fix:
Since the libarary needs to be able to work with processes that
have a notion of an xlator (THIS in particular) and without it,
care needs to be taken to allocate the global xlator when needed.
Moreover, the actual fix is to use the correct xlator context
in both cases. A new API is introduces when needs to be invoked
by the conusmer (although this could have been done during
register() call, keeping it a separate API makes thing flexible
and easy).

Test:
The issue is observed when a brick process goes offline. This is
triggered when test cases (.t's) are run in bulk, since each
test essestially spawns bricks processes (on volume start) and
terminates them (volume stop). Since bitrot daemon, as of now,
spawns upon volume start, the issue is much observed when the
volume is taken offline at the end of each test case. With this
fix, running the basic and core test cases along with building
the linux kernel has passed without daemon segfaults.

Thanks to Johnny (rabhat@) for helping in debugging the issue
(and with the fix :)).

Change-Id: I8d3022bf749590b2ee816504ed9b1dfccc65559a
BUG: 1170075
Signed-off-by: Venky Shankar <vshankar@redhat.com>
Reviewed-on: http://review.gluster.org/9953
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>

0 files changed, 0 insertions, 0 deletions