From:   Scott Mayhew <smayhew@redhat.com>
To:     bfields@fieldses.org, jlayton@kernel.org
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH] nfsd: CB_RECALL can race with FREE_STATEID
Date:   Thu, 18 Apr 2019 09:24:00 -0400
Message-Id: <20190418132400.24161-1-smayhew@redhat.com>
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk

While trying to track down some issues involving large numbers of
delegations being recalled/revoked, I caught the server setting
SEQ4_STATUS_CB_PATH_DOWN while the client was actively responding to
CB_RECALLs.  It turns out that the client had already done a
TEST_STATEID and FREE_STATEID for a delegation being recalled by the
time it received the CB_RECALL.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
---
 fs/nfsd/nfs4state.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 6a45fb00c5fc..e88e429133a8 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3958,6 +3958,14 @@ static int nfsd4_cb_recall_done(struct nfsd4_callback *cb,
 			rpc_delay(task, 2 * HZ);
 			return 0;
 		}
+		/*
+		 * Race: client may have done a FREE_STATEID before
+		 * receiving the CB_RECALL.
+		 */
+		if (dp->dl_stid.sc_type == NFS4_REVOKED_DELEG_STID &&
+				refcount_read(&dp->dl_stid.sc_count) == 1 &&
+				list_empty(&dp->dl_recall_lru))
+			return 1;
 		/*FALLTHRU*/
 	default:
 		return -1;
-- 
2.17.2