From 81f9b2a9a8c52d1c154cfc9bb957fcf556428ea9 Mon Sep 17 00:00:00 2001 From: Sagi Grimberg Date: Tue, 21 May 2024 23:20:28 +0300 Subject: [PATCH] nvmet: fix ns enable/disable possible hang [ Upstream commit f97914e35fd98b2b18fb8a092e0a0799f73afdfe ] When disabling an nvmet namespace, there is a period where the subsys->lock is released, as the ns disable waits for backend IO to complete, and the ns percpu ref to be properly killed. The original intent was to avoid taking the subsystem lock for a prolong period as other processes may need to acquire it (for example new incoming connections). However, it opens up a window where another process may come in and enable the ns, (re)intiailizing the ns percpu_ref, causing the disable sequence to hang. Solve this by taking the global nvmet_config_sem over the entire configfs enable/disable sequence. Fixes: a07b4970f464 ("nvmet: add a generic NVMe target") Signed-off-by: Sagi Grimberg Reviewed-by: Christoph Hellwig Reviewed-by: Chaitanya Kulkarni Signed-off-by: Keith Busch Signed-off-by: Sasha Levin --- drivers/nvme/target/configfs.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c index 5bdc3ba51f7e..a3d3a1bfd292 100644 --- a/drivers/nvme/target/configfs.c +++ b/drivers/nvme/target/configfs.c @@ -530,10 +530,18 @@ static ssize_t nvmet_ns_enable_store(struct config_item *item, if (strtobool(page, &enable)) return -EINVAL; + /* + * take a global nvmet_config_sem because the disable routine has a + * window where it releases the subsys-lock, giving a chance to + * a parallel enable to concurrently execute causing the disable to + * have a misaccounting of the ns percpu_ref. + */ + down_write(&nvmet_config_sem); if (enable) ret = nvmet_ns_enable(ns); else nvmet_ns_disable(ns); + up_write(&nvmet_config_sem); return ret ? ret : count; }