commit 58a437502736a026d6dac40d16f46572eea40088
author Gui Hecheng <guihecheng@cmss.chinamobile.com> Tue Nov 08 06:04:55 2016
committer Frank S. Filz <ffilzlnx@mindspring.com> Tue Nov 15 19:51:52 2016
tree 763cd12912289a9ab850e39f04c6a8104a83fa42
parent 4e14f0463a2832f3d127c477a42918488779647d

FSAL_VFS: fix segfault when export two subdirs with FSAL_VFS and FSAL_XFS

I export 2 subdirs /dir1, /dir2 of a xfs filesystem, /dir1 with FSAL_XFS
and /dir2 with FSAL_VFS. This export behavior results with only /dir1
exported successfully which is expected.
But when I try to do 'systemctl stop nfs-ganesha', I got a segfault:

kernel: ganesha.nfsd[58288]: segfault at 7f757901a340 ip 00007f757901a340 \
sp 00007f74ef4e94b8 error 15

This is because the failed export of /dir2 forgets to cleanup the export
entry of the FSAL_VFS module upon failure, and the destroy_fsals() got
bad pointers.

Adding a detach_export will fix it.
I tried to clarify the err return paths at the same time.

Change-Id: I02b91e19c789bbf34a8aeda14c3a3faba814bc8b
Signed-off-by: Gui Hecheng <guihecheng@cmss.chinamobile.com>