@@ -1022,6 +1022,9 @@ static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch)
struct cache_request *cr = container_of(cq, struct cache_request, q);
if (cr->item != ch)
continue;
+ if (test_bit(CACHE_PENDING, &ch->flags))
+ /* Lost a race and it is pending again */
+ break;
if (cr->readers != 0)
continue;
list_del(&cr->q.list);
@@ -1151,6 +1154,7 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
struct cache_request *crq;
char *bp;
int len;
+ int ret = 0;
if (!cache_listeners_exist(detail)) {
warn_no_listener(detail);
@@ -1182,10 +1186,18 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
crq->len = PAGE_SIZE - len;
crq->readers = 0;
spin_lock(&queue_lock);
- list_add_tail(&crq->q.list, &detail->queue);
+ if (test_bit(CACHE_PENDING, &h->flags))
+ list_add_tail(&crq->q.list, &detail->queue);
+ else
+ /* Lost a race, no longer PENDING, so don't enqueue */
+ ret = -EAGAIN;
spin_unlock(&queue_lock);
wake_up(&queue_wait);
- return 0;
+ if (ret == -EAGAIN) {
+ kfree(buf);
+ kfree(crq);
+ }
+ return ret;
}
EXPORT_SYMBOL_GPL(sunrpc_cache_pipe_upcall);
We currently queue an upcall after setting CACHE_PENDING, and dequeue after clearing CACHE_PENDING. So a request should only be present when CACHE_PENDING is set. However we don't combine the test and the enqueue/dequeue in a protected region, so it is possible (if unlikely) for a race to result in a request being queued without CACHE_PENDING set, or a request to be absent despite CACHE_PENDING. So: include a test for CACHE_PENDING inside the regions of enqueue and dequeue where queue_lock is held, and abort the operation if the value is not as expected. With this, it perfectly safe and correct to: - call cache_dequeue() if and only if we have just cleared CACHE_PENDING - call sunrpc_cache_pipe_upcall() (via cache_make_upcall) if and only if we have just set CACHE_PENDING. Reported-by: Bodo Stroesser <bstroesser@ts.fujitsu.com> Signed-off-by: NeilBrown <neilb@suse.de> --- net/sunrpc/cache.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html