From: Olga Kornievskaia <kolga@netapp.com>
Date: Thu, 20 Aug 2020 18:52:43 -0400
Subject: [PATCH] NFSv4.1 handle ERR_DELAY error reclaiming locking state on
 delegation recall
Git-commit: 3d7a9520f0c3e6a68b6de8c5812fc8b6d7a52626
Patch-mainline: v5.9
References: git-fixes

A client should be able to handle getting an ERR_DELAY error
while doing a LOCK call to reclaim state due to delegation being
recalled. This is a transient error that can happen due to server
moving its volumes and invalidating its file location cache and
upon reference to it during the LOCK call needing to do an
expensive lookup (leading to an ERR_DELAY error on a PUTFH).

Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/nfs4proc.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -6848,7 +6848,12 @@ int nfs4_lock_delegation_recall(struct f
 	err = nfs4_set_lock_state(state, fl);
 	if (err != 0)
 		return err;
-	err = _nfs4_do_setlk(state, F_SETLK, fl, NFS_LOCK_NEW);
+	do {
+		err = _nfs4_do_setlk(state, F_SETLK, fl, NFS_LOCK_NEW);
+		if (err != -NFS4ERR_DELAY)
+			break;
+		ssleep(1);
+	} while (err == -NFS4ERR_DELAY);
 	return nfs4_handle_delegation_recall_error(server, state, stateid, fl, err);
 }