This is a note to let you know that I've just added the patch titled
nvmet: fix ns enable/disable possible hang
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nvmet-fix-ns-enable-disable-possible-hang.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0f59a6f91f3db32abd7e55767458eb2777a54305
Author: Sagi Grimberg <sagi@xxxxxxxxxxx>
Date: Tue May 21 23:20:28 2024 +0300
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 <sagi@xxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 5bdc3ba51f7ef..a3d3a1bfd292d 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;
}
