From 5e416b11b4a941040ee04a5f2883df3980a3f733 Mon Sep 17 00:00:00 2001 From: Anton Eidelman Date: Mon, 12 Aug 2019 23:00:36 +0300 Subject: [PATCH] nvme-multipath: fix possible I/O hang when paths are updated [ Upstream commit 504db087aaccdb32af61539916409f7dca31ceb5 ] nvme_state_set_live() making a path available triggers requeue_work in order to resubmit requests that ended up on requeue_list when no paths were available. This requeue_work may race with concurrent nvme_ns_head_make_request() that do not observe the live path yet. Such concurrent requests may by made by either: - New IO submission. - Requeue_work triggered by nvme_failover_req() or another ana_work. A race may cause requeue_work capture the state of requeue_list before more requests get onto the list. These requests will stay on the list forever unless requeue_work is triggered again. In order to prevent such race, nvme_state_set_live() should synchronize_srcu(&head->srcu) before triggering the requeue_work and prevent nvme_ns_head_make_request referencing an old snapshot of the path list. Reviewed-by: Christoph Hellwig Signed-off-by: Anton Eidelman Signed-off-by: Sagi Grimberg Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/nvme/host/multipath.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index 05d6371..f57feb8 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -323,6 +323,7 @@ static void nvme_mpath_set_live(struct nvme_ns *ns) "failed to create id group.\n"); } + synchronize_srcu(&ns->head->srcu); kblockd_schedule_work(&ns->head->requeue_work); } -- 2.7.4