[PATCH 2/2] nfsd: only set file_lock.fl_lmops in nfsd4_lockt if a stateowner is found

[Jeff Layton <jlayton@redhat.com>]

nfsd4_lockt does a search for a lockstateowner when building the lock
struct to test. If one is found, it'll set fl_owner to it. Regardless of
whether that happens, it'll also set fl_lmops.

If a lockstateowner is not found, then we'll have fl_owner set to NULL
and fl_lmops set pointing to nfsd_posix_mng_ops. Other parts of the
NFSv4 server code assume that fl_owner will point to a valid
nfs4_stateowner if fl_lmops is set this way.

This behavior exposed a bug in DLM's GETLK implementation where it
wasn't clearing out the fields in the file_lock before filling in
conflicting lock info. While we were able to fix this in DLM, it
still seems pointless and dangerous to set the fl_lmops this way
when we have a NULL lockstateowner.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 fs/nfsd/nfs4state.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 88db7d3..07d196a 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -2867,11 +2867,13 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 
 	lockt->lt_stateowner = find_lockstateowner_str(inode,
 			&lockt->lt_clientid, &lockt->lt_owner);
-	if (lockt->lt_stateowner)
+	if (lockt->lt_stateowner) {
 		file_lock.fl_owner = (fl_owner_t)lockt->lt_stateowner;
+		file_lock.fl_lmops = &nfsd_posix_mng_ops;
+	}
+
 	file_lock.fl_pid = current->tgid;
 	file_lock.fl_flags = FL_POSIX;
-	file_lock.fl_lmops = &nfsd_posix_mng_ops;
 
 	file_lock.fl_start = lockt->lt_offset;
 	file_lock.fl_end = last_byte_offset(lockt->lt_offset, lockt->lt_length);
-- 
1.5.5.6