nfs3: NULL fdentry check before removing from fdcache

Suppose a file name 1 is created and some data is written to it. After this
another 512 files are newly created and written to. When the the 513th file is
created and an fd_t opened for it, it results in 1's fd_t being replaced in the
fd-lru with 513th file's fd_t. This is the correct behaviour resulting in all
refs getting unref from the fd_t of 1 and the fd and all related state being
freed.

But, in some workloads, some refs are still pending even after the fd_t is
removed from LRU, resulting in the fd still being bound to the inode. In
nfs3svc_remove_cbk, while removing the inode state, we also ensure that any
fd_ts in the cache for this inode are also removed. While removing the fd_t,
this situation where the fd_t has replaced with another, even while a ref
remains on the fd_t, results in a crash in the fdcache_remove path in
nfs3svc_remove_cbk. This happens because the fd_ctx_get results in a NULL value
because the ctx was already deleted when this fd_t was removed from fd-lru
earlier. This patch fixes the crash by introducing a NULL check.

Signed-off-by: Shehjar Tikoo <shehjart@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 885 ([NFS Xlator] Crash in nfs3_fdcache_update)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=885

0 files changed, 0 insertions, 0 deletions