nfsd4: use recall_lock for delegation hashing

commit 931ee56c67573eb4e51c8a4e78598d965b8b059e upstream.

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>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
[bwh: Backported to 3.2:
 - Adjust context
 - Also remove a list_del_init() in nfs4_setlease() which would now be
   before the corresponding list_add()
 - Drop change to nfsd_find_all_delegations(), which doesn't exist]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index b2e0a5585aed63b7db6c92a8fb1508df750938b9..7e1a7a8f23700b15af7eb74cdd4c59e7df56e60f 100644 (file)
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -337,13 +337,22 @@ static void unhash_stid(struct nfs4_stid *s)
        idr_remove(stateids, s->sc_stateid.si_opaque.so_id);
 }
 
+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)
 {
        unhash_stid(&dp->dl_stid);
-       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);
@@ -2810,10 +2819,8 @@ static int nfs4_setlease(struct nfs4_delegation *dp, int flag)
        if (!fl)
                return -ENOMEM;
        fl->fl_file = find_readable_file(fp);
-       list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
        status = vfs_setlease(fl->fl_file, fl->fl_type, &fl);
        if (status) {
-               list_del_init(&dp->dl_perclnt);
                locks_free_lock(fl);
                return -ENOMEM;
        }
@@ -2821,7 +2828,9 @@ static int nfs4_setlease(struct nfs4_delegation *dp, int flag)
        fp->fi_deleg_file = fl->fl_file;
        get_file(fp->fi_deleg_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;
 }
 
@@ -2837,9 +2846,8 @@ static int nfs4_set_delegation(struct nfs4_delegation *dp, int flag)
                return -EAGAIN;
        }
        atomic_inc(&fp->fi_delegees);
-       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;
 }