pNFS: Always free the session slot on error in nfs4_layoutget_handle_exception

pNFS: Always free the session slot on error in nfs4_layoutget_handle_exception

[ Upstream commit 2dbf8dffbf35fd8f611083b9d9fe74fdccf912a3 ]

Right now, we can call nfs_commit_inode() while holding the session slot,
which could lead to NFSv4 deadlocks. Ensure we only keep the slot if
the server returned a layout that we have to process.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>