[PATCH 10/23] nvmet: add context annotation for nvmet_ns::nguid

[Nilay Shroff]

The nvmet_ns::nguid field is protected by nvmet_subsys::lock. Annotate
it with __guarded_by(&subsys->lock) so that the clang context analyzer
can validate accesses to this field.

Some accesses to nvmet_ns::nguid in the I/O hotpath do not require
holding nvmet_subsys::lock, as the namespace reference guarantees that
the namespace remains valid and the field is not modified while I/O is
in flight. However, the clang context analyzer cannot express this
access pattern directly.

Introduce nvmet_ns_nguid() as an inline helper annotated with
__context_unsafe() to allow these accesses without requiring the
subsystem lock. Convert the relevant accesses in the I/O hotpath and
request-processing paths to use this helper.

Additionally, acquire ns->subsys->lock in nvmet_ns_device_nguid_show()
before accessing ns->nguid, since this configfs control path does not
hold the lock.

Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
---
 drivers/nvme/target/admin-cmd.c | 7 ++++---
 drivers/nvme/target/configfs.c  | 9 ++++++++-
 drivers/nvme/target/nvmet.h     | 4 +++-
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 7cdf13351678..d784498ca720 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -934,7 +934,7 @@ static void nvmet_execute_identify_ns(struct nvmet_req *req)
 	 */
 	id->endgid = cpu_to_le16(nvmet_ns_nsid(req->ns));
 
-	memcpy(&id->nguid, &req->ns->nguid, sizeof(id->nguid));
+	memcpy(&id->nguid, nvmet_ns_nguid(req->ns), sizeof(id->nguid));
 
 	id->lbaf[0].ds = nvmet_ns_blksize_shift(req->ns);
 
@@ -1094,10 +1094,11 @@ static void nvmet_execute_identify_desclist(struct nvmet_req *req)
 		if (status)
 			goto out;
 	}
-	if (memchr_inv(req->ns->nguid, 0, sizeof(req->ns->nguid))) {
+	if (memchr_inv(nvmet_ns_nguid(req->ns), 0, sizeof(req->ns->nguid))) {
 		status = nvmet_copy_ns_identifier(req, NVME_NIDT_NGUID,
 						  NVME_NIDT_NGUID_LEN,
-						  &req->ns->nguid, &off);
+						  nvmet_ns_nguid(req->ns),
+						  &off);
 		if (status)
 			goto out;
 	}
diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 27c50fa533e7..cd2c301bc69a 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -643,7 +643,14 @@ CONFIGFS_ATTR(nvmet_ns_, device_uuid);
 
 static ssize_t nvmet_ns_device_nguid_show(struct config_item *item, char *page)
 {
-	return sprintf(page, "%pUb\n", &to_nvmet_ns(item)->nguid);
+	struct nvmet_ns *ns = to_nvmet_ns(item);
+	ssize_t ret;
+
+	mutex_lock(&ns->subsys->lock);
+	ret = sprintf(page, "%pUb\n", &ns->nguid);
+	mutex_unlock(&ns->subsys->lock);
+
+	return ret;
 }
 
 static ssize_t nvmet_ns_device_nguid_store(struct config_item *item,
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 59adf99470f8..21ed96b39a31 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -163,7 +163,8 @@ struct nvmet_ns {
 		__guarded_by(&subsys->lock);
 	loff_t			size
 		__guarded_by(&subsys->lock);
-	u8			nguid[16];
+	u8			nguid[16]
+		__guarded_by(&subsys->lock);
 	uuid_t			uuid;
 	u32			anagrpid;
 
@@ -210,6 +211,7 @@ NVMET_NS_ACCESSOR(struct block_device *, bdev)
 NVMET_NS_ACCESSOR(struct file *, file)
 NVMET_NS_ACCESSOR(u32, nsid)
 NVMET_NS_ACCESSOR(u32, blksize_shift)
+NVMET_NS_ACCESSOR(u8 *, nguid)
 
 /*
  * These accessors use data_race() and READ_ONCE() to allow lockless access to
-- 
2.53.0