[PATCH 3.2 058/125] nfsd4: use recall_lock for delegation hashing

Ben Hutchings
2014-07-08T19:19:24Z

From: Benny Halevy <bhalevy@primarydata.com>

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>
---
fs/nfsd/nfs4state.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -337,13 +337,22 @@ static void unhash_stid(struct nfs4_stid
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_del
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_del
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 nf
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;
}