[PATCH 16/23] nvmet: fix access to nvmet_ns::enable using nvmet_subsys::lock

[Nilay Shroff <nilay@linux.ibm.com>]

nvmet_ns::enable is protected by nvmet_subsys::lock. The clang
context analyser complains about accessing ns->enabled without
subsys->lock in nvmet_ns_enable_show():

drivers/nvme/target/configfs.c:741:50: error: reading variable 'enabled' requires holding mutex 'to_nvmet_ns(item).subsys->lock'
      [-Werror,-Wthread-safety-analysis]
  741 |         return sprintf(page, "%d\n", to_nvmet_ns(item)->enabled);
      |                                                         ^

Fix the above error by acquiring ns->susbsys->lock before
accessing ns->enabled in nvmet_ns_enable_show().

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/target/configfs.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 34d79fadbf15..ba44d404ad56 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -737,7 +737,14 @@ CONFIGFS_ATTR(nvmet_ns_, ana_grpid);
 
 static ssize_t nvmet_ns_enable_show(struct config_item *item, char *page)
 {
-	return sprintf(page, "%d\n", to_nvmet_ns(item)->enabled);
+	struct nvmet_ns *ns = to_nvmet_ns(item);
+	ssize_t ret;
+
+	mutex_lock(&ns->subsys->lock);
+	ret = sprintf(page, "%d\n", ns->enabled);
+	mutex_unlock(&ns->subsys->lock);
+
+	return ret;
 }
 
 static ssize_t nvmet_ns_enable_store(struct config_item *item,
-- 
2.53.0