nfsd: bump dl_time when unhashing delegation
There's a potential race between a lease break and DELEGRETURN call.
Suppose a lease break comes in and queues the workqueue job for a
delegation, but it doesn't run just yet. Then, a DELEGRETURN comes in
finds the delegation and calls destroy_delegation on it to unhash it and
put its primary reference.
Next, the workqueue job runs and queues the delegation back onto the
del_recall_lru list, issues the CB_RECALL and puts the final reference.
With that, the final reference to the delegation is put, but it's still
on the LRU list.
When we go to unhash a delegation, it's because we intend to get rid of
it soon afterward, so we don't want lease breaks to mess with it once
that occurs. Fix this by bumping the dl_time whenever we unhash a
delegation, to ensure that lease breaks don't monkey with it.
I believe this is a regression due to commit 02e1215f9f7 (nfsd: Avoid
taking state_lock while holding inode lock in nfsd_break_one_deleg).
Prior to that, the state_lock was held in the lm_break callback itself,
and that would have prevented this race.
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 72da0d4..a3a828d 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -660,6 +660,8 @@
spin_lock(&state_lock);
dp->dl_stid.sc_type = NFS4_CLOSED_DELEG_STID;
+ /* Ensure that deleg break won't try to requeue it */
+ ++dp->dl_time;
spin_lock(&fp->fi_lock);
list_del_init(&dp->dl_perclnt);
list_del_init(&dp->dl_recall_lru);