Commit 2181e455 authored Jun 20, 2019 by Anton Eidelman Committed by Christoph Hellwig Jun 21, 2019

nvme: fix possible io failures when removing multipathed ns



When a shared namespace is removed, we call blk_cleanup_queue()
when the device can still be accessed as the current path and this can
result in submission to a dying queue. Hence, direct_make_request()
called by our mpath device may fail (propagating the failure to userspace).
Instead, we want to failover this I/O to a different path if one exists.
Thus, before we cleanup the request queue, we make sure that the device is
cleared from the current path nor it can be selected again as such.

Fix this by:
- clear the ns from the head->list and synchronize rcu to make sure there is
  no concurrent path search that restores it as the current path
- clear the mpath current path in order to trigger a subsequent path search
  and sync srcu to wait for any ongoing request submissions
- safely continue to namespace removal and blk_cleanup_queue

Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

parent 4bea364f

drivers/nvme/host/core.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -3344,6 +3344,14 @@ static void nvme_ns_remove(struct nvme_ns *ns)
		return;

		nvme_fault_inject_fini(ns);

		mutex_lock(&ns->ctrl->subsys->lock);
		list_del_rcu(&ns->siblings);
		mutex_unlock(&ns->ctrl->subsys->lock);
		synchronize_rcu(); /* guarantee not available in head->list */
		nvme_mpath_clear_current_path(ns);
		synchronize_srcu(&ns->head->srcu); /* wait for concurrent submissions */

		if (ns->disk && ns->disk->flags & GENHD_FL_UP) {
		del_gendisk(ns->disk);
		blk_cleanup_queue(ns->queue);
		@@ -3351,16 +3359,10 @@ static void nvme_ns_remove(struct nvme_ns *ns)
		blk_integrity_unregister(ns->disk);
		}

		mutex_lock(&ns->ctrl->subsys->lock);
		list_del_rcu(&ns->siblings);
		nvme_mpath_clear_current_path(ns);
		mutex_unlock(&ns->ctrl->subsys->lock);

		down_write(&ns->ctrl->namespaces_rwsem);
		list_del_init(&ns->list);
		up_write(&ns->ctrl->namespaces_rwsem);

		synchronize_srcu(&ns->head->srcu);
		nvme_mpath_check_last_path(ns);
		nvme_put_ns(ns);
		}

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