From b401be22b5cf059290ee98106bc780e087407d45 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Tue, 29 Jul 2014 21:34:33 -0400 Subject: [PATCH] nfsd: don't allow CLOSE to proceed until refcount on stateid drops 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 Signed-off-by: J. Bruce Fields --- fs/nfsd/nfs4state.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index b61319401826..6d26d26751f5 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -85,6 +85,12 @@ 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; @@ -640,8 +646,10 @@ 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; + } idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id); spin_unlock(&clp->cl_lock); s->sc_free(s); @@ -3070,6 +3078,17 @@ 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); -- 2.34.1