[PATCH 17/23] nvmet: add context annotation for nvmet_ns::device_path

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

The nvmet_ns::device_path field is protected by
nvmet_subsys::lock. Annotate it with
__guarded_by(&subsys->lock) to allow the Clang context
analyzer to validate accesses to this field.

Some request-processing paths access ns->device_path without
holding subsys->lock. This is safe because the namespace
reference held by the request prevents the ns->device_path from
being modified while I/O is in flight. However, the context
analyzer cannot express this access pattern directly.

Introduce nvmet_ns_device_path() as an inline helper
annotated with __context_unsafe() to allow these lockless
accesses without triggering context analyzer warnings.

Additionally, update __assign_req_name() to use this accessor
when copying device_path into the trace event's request name.
This is safe because the tracing function is invoked after
the namespace reference has been acquired.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/target/nvmet.h | 4 +++-
 drivers/nvme/target/trace.h | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index a6fb3aab0c5d..fa932c1fbf29 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -176,7 +176,8 @@ struct nvmet_ns {
 #define NVMET_NS_IO_LIVE	0
 	unsigned long		flags;
 	struct nvmet_subsys	*subsys;
-	const char		*device_path;
+	const char		*device_path
+		__guarded_by(&subsys->lock);
 
 	struct config_group	device_group;
 	struct config_group	group;
@@ -217,6 +218,7 @@ NVMET_NS_ACCESSOR(u32, blksize_shift)
 NVMET_NS_ACCESSOR(u8 *, nguid)
 NVMET_NS_ACCESSOR(uuid_t, uuid)
 NVMET_NS_ACCESSOR(bool, buffered_io)
+NVMET_NS_ACCESSOR(const char *, device_path)
 
 /*
  * These accessors use data_race() and READ_ONCE() to allow lockless access to
diff --git a/drivers/nvme/target/trace.h b/drivers/nvme/target/trace.h
index 7f7ebf9558e5..b15294e24793 100644
--- a/drivers/nvme/target/trace.h
+++ b/drivers/nvme/target/trace.h
@@ -59,7 +59,7 @@ static inline void __assign_req_name(char *name, struct nvmet_req *req)
 		return;
 	}
 
-	strscpy_pad(name, req->ns->device_path, DISK_NAME_LEN);
+	strscpy_pad(name, nvmet_ns_device_path(req->ns), DISK_NAME_LEN);
 }
 #endif
 
-- 
2.53.0