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nfsd: don't allow CLOSE to proceed until refcount on stateid drops

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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@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Jeff Layton 2014-07-29 21:34:33 -04:00 committed by J. Bruce Fields
parent d3134b1049
commit b401be22b5
1 changed files with 20 additions and 1 deletions
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21
fs/nfsd/nfs4state.c
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@ -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);