Commit b7b9c227 authored Apr 25, 2016 by Ming Lin Committed by Jens Axboe May 02, 2016

nvme: fix nvme_ns_remove() deadlock



On receipt of a namespace attribute changed AER, we acquire the
namespace mutex lock before proceeding to scan and validate the
namespace list. In case of namespace detach/delete command,
nvme_ns_remove function deadlocks trying to acquire the already held
lock.

All callers, except nvme_remove_namespaces(), of nvme_ns_remove()
already held namespaces_mutex. So we can simply fix the deadlock by
not acquiring the mutex in nvme_ns_remove() and acquiring it in
nvme_remove_namespaces().

Reported-by: Sunad Bhandary S <sunad.s@samsung.com>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimerg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent 0bf77e9d

drivers/nvme/host/core.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -1452,6 +1452,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)

		static void nvme_ns_remove(struct nvme_ns *ns)
		{
		lockdep_assert_held(&ns->ctrl->namespaces_mutex);

		if (test_and_set_bit(NVME_NS_REMOVING, &ns->flags))
		return;

		@@ -1464,9 +1466,7 @@ static void nvme_ns_remove(struct nvme_ns *ns)
		blk_mq_abort_requeue_list(ns->queue);
		blk_cleanup_queue(ns->queue);
		}
		mutex_lock(&ns->ctrl->namespaces_mutex);
		list_del_init(&ns->list);
		mutex_unlock(&ns->ctrl->namespaces_mutex);
		synchronize_rcu();
		nvme_put_ns(ns);
		}
		@@ -1580,8 +1580,10 @@ void nvme_remove_namespaces(struct nvme_ctrl *ctrl)
		{
		struct nvme_ns ns, next;

		mutex_lock(&ctrl->namespaces_mutex);
		list_for_each_entry_safe(ns, next, &ctrl->namespaces, list)
		nvme_ns_remove(ns);
		mutex_unlock(&ctrl->namespaces_mutex);
		}
		EXPORT_SYMBOL_GPL(nvme_remove_namespaces);

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