[PATCH 20/23] nvmet: fix PCI P2P parameters access using nvmet_subsys::lock

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

The nvmet_ns::p2p_dev and nvmet_ns::use_p2pmem fields are protected by
nvmet_subsys::lock. However, nvmet_ns_p2pmem_show() accesses these
fields without holding the corresponding lock, triggering Clang context
analyzer errors:

drivers/nvme/target/configfs.c:587:42: error: reading variable 'p2p_dev' requires holding mutex 'to_nvmet_ns(item).subsys->lock'
      [-Werror,-Wthread-safety-analysis]
  587 |         return pci_p2pdma_enable_show(page, ns->p2p_dev, ns->use_p2pmem);
      |                                                 ^
drivers/nvme/target/configfs.c:587:55: error: reading variable 'use_p2pmem' requires holding mutex 'to_nvmet_ns(item).subsys->lock'
      [-Werror,-Wthread-safety-analysis]
  587 |         return pci_p2pdma_enable_show(page, ns->p2p_dev, ns->use_p2pmem);
      |                                                              ^

Fix the above errors by acquiring ns->subsys->lock before accessing
PCI P2P parameters in nvmet_ns_p2pmem_show().

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/target/configfs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index a87917381093..7245db64b8dc 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -582,8 +582,13 @@ CONFIGFS_ATTR(nvmet_ns_, device_path);
 static ssize_t nvmet_ns_p2pmem_show(struct config_item *item, char *page)
 {
 	struct nvmet_ns *ns = to_nvmet_ns(item);
+	ssize_t ret;
 
-	return pci_p2pdma_enable_show(page, ns->p2p_dev, ns->use_p2pmem);
+	mutex_lock(&ns->subsys->lock);
+	ret = pci_p2pdma_enable_show(page, ns->p2p_dev, ns->use_p2pmem);
+	mutex_unlock(&ns->subsys->lock);
+
+	return ret;
 }
 
 static ssize_t nvmet_ns_p2pmem_store(struct config_item *item,
-- 
2.53.0