NFSv4.1: Don't lose locks when a server reboots during delegation return

If the server reboots while we are converting a delegation into
OPEN/LOCK stateids as part of a delegation return, the current code
will simply exit with an error. This causes us to lose both
delegation state and locking state (i.e. locking atomicity).

Deal with this by exposing the delegation stateid during delegation
return, so that we can recover the delegation, and then resume
open/lock recovery.

Note that not having to hold the nfs_inode->rwsem across the
calls to nfs_delegation_claim_opens() also fixes a deadlock against
the NFSv4.1 reboot recovery code.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 92584c1ea725..a1e89e270ad8 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -896,6 +896,8 @@ static int can_open_delegated(struct nfs_delegation *delegation, fmode_t fmode)
                 return 0;
         if (test_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags))
                 return 0;
+        if (test_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
+                return 0;
         nfs_mark_delegation_referenced(delegation);
         return 1;
 }
@@ -973,6 +975,7 @@ static int update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_stat
 
         spin_lock(&deleg_cur->lock);
         if (nfsi->delegation != deleg_cur ||
+           test_bit(NFS_DELEGATION_RETURNING, &deleg_cur->flags) ||
             (deleg_cur->type & fmode) != fmode)
                 goto no_delegation_unlock;