nfsd4: use recall_lock for delegation hashing

This fixes a bug in the handling of the fi_delegations list.

nfs4_setlease does not hold the recall_lock when adding to it. The
client_mutex is held, which prevents against concurrent list changes,
but nfsd_break_deleg_cb does not hold while walking it. New delegations
could theoretically creep onto the list while we're walking it there.

Signed-off-by: Benny Halevy <bhalevy@primarydata.com>
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 15 insertions, 5 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 01a0e4384500..05ca64c4599d 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -433,12 +433,21 @@ static void unhash_stid(struct nfs4_stid *s)
         s->sc_type = 0;
 }
 
+static void
+hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
+{
+        lockdep_assert_held(&recall_lock);
+
+        list_add(&dp->dl_perfile, &fp->fi_delegations);
+        list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
+}
+
 /* Called under the state lock. */
 static void
 unhash_delegation(struct nfs4_delegation *dp)
 {
-        list_del_init(&dp->dl_perclnt);
         spin_lock(&recall_lock);
+        list_del_init(&dp->dl_perclnt);
         list_del_init(&dp->dl_perfile);
         list_del_init(&dp->dl_recall_lru);
         spin_unlock(&recall_lock);
@@ -3065,11 +3074,12 @@ static int nfs4_setlease(struct nfs4_delegation *dp)
         status = vfs_setlease(fl->fl_file, fl->fl_type, &fl);
         if (status)
                 goto out_free;
-        list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
         fp->fi_lease = fl;
         fp->fi_deleg_file = get_file(fl->fl_file);
         atomic_set(&fp->fi_delegees, 1);
-        list_add(&dp->dl_perfile, &fp->fi_delegations);
+        spin_lock(&recall_lock);
+        hash_delegation_locked(dp, fp);
+        spin_unlock(&recall_lock);
         return 0;
 out_free:
         locks_free_lock(fl);
@@ -3090,9 +3100,8 @@ static int nfs4_set_delegation(struct nfs4_delegation *dp, struct nfs4_file *fp)
                 spin_unlock(&recall_lock);
                 return -EAGAIN;
         }
-        list_add(&dp->dl_perfile, &fp->fi_delegations);
+        hash_delegation_locked(dp, fp);
         spin_unlock(&recall_lock);
-        list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
         return 0;
 }
 
@@ -4903,6 +4912,7 @@ static u64 nfsd_find_all_delegations(struct nfs4_client *clp, u64 max,
         struct nfs4_delegation *dp, *next;
         u64 count = 0;
 
+        lockdep_assert_held(&recall_lock);
         list_for_each_entry_safe(dp, next, &clp->cl_delegations, dl_perclnt) {
                 if (victims)
                         list_move(&dp->dl_recall_lru, victims);