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nfsd: ensure that delegation stateid hash references are only put once

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It's possible that a DELEGRETURN could race with (e.g.) client expiry,
in which case we could end up putting the delegation hash reference more
than once.

Have unhash_delegation_locked return a bool that indicates whether it
was already unhashed. In the case of destroy_delegation we only
conditionally put the hash reference if that returns true.

The other callers of unhash_delegation_locked call it while walking
list_heads that shouldn't yet be detached. If we find that it doesn't
return true in those cases, then throw a WARN_ON as that indicates that
we have a partially hashed delegation, and that something is likely very
wrong.

Tested-by: Andrew W Elble <aweits@rit.edu>
Tested-by: Anna Schumaker <Anna.Schumaker@netapp.com>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Jeff Layton 2015-08-24 12:41:48 -04:00 committed by J. Bruce Fields
parent e85687393f
commit 3fcbbd244e
1 changed files with 17 additions and 9 deletions
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26
fs/nfsd/nfs4state.c
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@ -777,13 +777,16 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
}
static void
static bool
unhash_delegation_locked(struct nfs4_delegation *dp)
{
struct nfs4_file *fp = dp->dl_stid.sc_file;
lockdep_assert_held(&state_lock);
if (list_empty(&dp->dl_perfile))
return false;
dp->dl_stid.sc_type = NFS4_CLOSED_DELEG_STID;
/* Ensure that deleg break won't try to requeue it */
++dp->dl_time;
@ -792,16 +795,21 @@ unhash_delegation_locked(struct nfs4_delegation *dp)
list_del_init(&dp->dl_recall_lru);
list_del_init(&dp->dl_perfile);
spin_unlock(&fp->fi_lock);
return true;
}
static void destroy_delegation(struct nfs4_delegation *dp)
{
bool unhashed;
spin_lock(&state_lock);
unhash_delegation_locked(dp);
unhashed = unhash_delegation_locked(dp);
spin_unlock(&state_lock);
put_clnt_odstate(dp->dl_clnt_odstate);
nfs4_put_deleg_lease(dp->dl_stid.sc_file);
nfs4_put_stid(&dp->dl_stid);
if (unhashed) {
put_clnt_odstate(dp->dl_clnt_odstate);
nfs4_put_deleg_lease(dp->dl_stid.sc_file);
nfs4_put_stid(&dp->dl_stid);
}
}
static void revoke_delegation(struct nfs4_delegation *dp)
@ -1730,7 +1738,7 @@ __destroy_client(struct nfs4_client *clp)
spin_lock(&state_lock);
while (!list_empty(&clp->cl_delegations)) {
dp = list_entry(clp->cl_delegations.next, struct nfs4_delegation, dl_perclnt);
unhash_delegation_locked(dp);
WARN_ON(!unhash_delegation_locked(dp));
list_add(&dp->dl_recall_lru, &reaplist);
}
spin_unlock(&state_lock);
@ -4357,7 +4365,7 @@ nfs4_laundromat(struct nfsd_net *nn)
new_timeo = min(new_timeo, t);
break;
}
unhash_delegation_locked(dp);
WARN_ON(!unhash_delegation_locked(dp));
list_add(&dp->dl_recall_lru, &reaplist);
}
spin_unlock(&state_lock);
@ -6314,7 +6322,7 @@ static u64 nfsd_find_all_delegations(struct nfs4_client *clp, u64 max,
continue;
atomic_inc(&clp->cl_refcount);
unhash_delegation_locked(dp);
WARN_ON(!unhash_delegation_locked(dp));
list_add(&dp->dl_recall_lru, victims);
}
++count;
@ -6645,7 +6653,7 @@ nfs4_state_shutdown_net(struct net *net)
spin_lock(&state_lock);
list_for_each_safe(pos, next, &nn->del_recall_lru) {
dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru);
unhash_delegation_locked(dp);
WARN_ON(!unhash_delegation_locked(dp));
list_add(&dp->dl_recall_lru, &reaplist);
}
spin_unlock(&state_lock);