Once we remove client_mutex protection, it'll be possible to have an
in-flight operation using an openstateid when a CLOSE call comes in.
If that happens, we can't just put the sc_file reference and clear its
pointer without risking an oops.
Fix this by ensuring that v4.0 CLOSE operations wait for the refcount
to drop before proceeding to do so.
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
---
fs/nfsd/nfs4state.c | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 2a03efc42803..296d75d93de4 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -86,6 +86,12 @@ static DEFINE_MUTEX(client_mutex);
*/
static DEFINE_SPINLOCK(state_lock);
+/*
+ * A waitqueue for all in-progress 4.0 CLOSE operations that are waiting for
+ * the refcount on the open stateid to drop.
+ */
+static DECLARE_WAIT_QUEUE_HEAD(close_wq);
+
static struct kmem_cache *openowner_slab;
static struct kmem_cache *lockowner_slab;
static struct kmem_cache *file_slab;
@@ -662,8 +668,10 @@ static void nfs4_put_stid(struct nfs4_stid *s)
might_lock(&clp->cl_lock);
- if (!atomic_dec_and_lock(&s->sc_count, &clp->cl_lock))
+ if (!atomic_dec_and_lock(&s->sc_count, &clp->cl_lock)) {
+ wake_up_all(&close_wq);
return;
+ }
remove_stid_locked(clp, s);
spin_unlock(&clp->cl_lock);
s->sc_free(s);
@@ -3090,11 +3098,23 @@ move_to_close_lru(struct nfs4_ol_stateid *s, struct net *net)
dprintk("NFSD: move_to_close_lru nfs4_openowner %p\n", oo);
+ /*
+ * We know that we hold one reference via nfsd4_close, and another
+ * "persistent" reference for the client. If the refcount is higher
+ * than 2, then there are still calls in progress that are using this
+ * stateid. We can't put the sc_file reference until they are finished.
+ * Wait for the refcount to drop to 2. Since it has been unhashed,
+ * there should be no danger of the refcount going back up again at
+ * this point.
+ */
+ wait_event(close_wq, atomic_read(&s->st_stid.sc_count) == 2);
+
release_all_access(s);
if (s->st_stid.sc_file) {
put_nfs4_file(s->st_stid.sc_file);
s->st_stid.sc_file = NULL;
}
+
release_last_closed_stateid(oo);
oo->oo_last_closed_stid = s;
list_move_tail(&oo->oo_close_lru, &nn->close_lru);
--
1.9.3
--
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