From d55a166c961714e18907f4723252f72097cd2d23 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Tue, 22 Jul 2014 13:52:06 -0400 Subject: [PATCH] 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 Signed-off-by: Jeff Layton Signed-off-by: J. Bruce Fields --- fs/nfsd/nfs4state.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 72da0d44e66b..a3a828d17563 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -660,6 +660,8 @@ unhash_delegation(struct nfs4_delegation *dp) 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); -- 2.20.1