NFSv4.1: Keep a reference on lock states while checking

While walking the list of lock_states, keep a reference on each
nfs4_lock_state to be checked, otherwise the lock state could be removed
while the check performs TEST_STATEID and possible FREE_STATEID.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 2d1481eb1929..e6dc95e0f97e 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2564,15 +2564,23 @@ static void nfs41_check_delegation_stateid(struct nfs4_state *state)
 static int nfs41_check_expired_locks(struct nfs4_state *state)
 {
         int status, ret = NFS_OK;
-        struct nfs4_lock_state *lsp;
+        struct nfs4_lock_state *lsp, *prev = NULL;
         struct nfs_server *server = NFS_SERVER(state->inode);
 
         if (!test_bit(LK_STATE_IN_USE, &state->flags))
                 goto out;
+
+        spin_lock(&state->state_lock);
         list_for_each_entry(lsp, &state->lock_states, ls_locks) {
                 if (test_bit(NFS_LOCK_INITIALIZED, &lsp->ls_flags)) {
                         struct rpc_cred *cred = lsp->ls_state->owner->so_cred;
 
+                        atomic_inc(&lsp->ls_count);
+                        spin_unlock(&state->state_lock);
+
+                        nfs4_put_lock_state(prev);
+                        prev = lsp;
+
                         status = nfs41_test_and_free_expired_stateid(server,
                                         &lsp->ls_stateid,
                                         cred);
@@ -2585,10 +2593,14 @@ static int nfs41_check_expired_locks(struct nfs4_state *state)
                                         set_bit(NFS_LOCK_LOST, &lsp->ls_flags);
                         } else if (status != NFS_OK) {
                                 ret = status;
-                                break;
+                                nfs4_put_lock_state(prev);
+                                goto out;
                         }
+                        spin_lock(&state->state_lock);
                 }
-        };
+        }
+        spin_unlock(&state->state_lock);
+        nfs4_put_lock_state(prev);
 out:
         return ret;
 }