[PATCH v4 18/20] nvme: add context annotations in tcp.c

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

The nvme_tcp_ctrl_list and nvme_tcp_ctrl::list are protected by
nvme_tcp_ctrl_mutex. Define nvme_tcp_ctrl_list using
LIST_HEAD_GUARDED(nvme_tcp_ctrl_list, nvme_tcp_ctrl_mutex) and
annotate nvme_tcp_ctrl::list using
__guarded_by(&nvme_tcp_ctrl_mutex) so that Clang's context analysis
can validate accesses against the corresponding locking requirements.

It is safe to initialize nvme_tcp_ctrl::list while allocating the
controller object because the list entry has not yet been added to
nvme_tcp_ctrl_list. Annotate the initialization with context_unsafe()
to suppress the corresponding Clang warning.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/host/tcp.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index ba5c7b3e2a7c..8d2fbfc7cd8d 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -149,13 +149,17 @@ struct nvme_tcp_queue {
 #endif
 };
 
+static DEFINE_MUTEX(nvme_tcp_ctrl_mutex);
+static LIST_HEAD_GUARDED(nvme_tcp_ctrl_list, nvme_tcp_ctrl_mutex);
+
 struct nvme_tcp_ctrl {
 	/* read only in the hot path */
 	struct nvme_tcp_queue	*queues;
 	struct blk_mq_tag_set	tag_set;
 
 	/* other member variables */
-	struct list_head	list;
+	struct list_head	list
+		__guarded_by(&nvme_tcp_ctrl_mutex);
 	struct blk_mq_tag_set	admin_tag_set;
 	struct sockaddr_storage addr;
 	struct sockaddr_storage src_addr;
@@ -167,8 +171,6 @@ struct nvme_tcp_ctrl {
 	u32			io_queues[HCTX_MAX_TYPES];
 };
 
-static LIST_HEAD(nvme_tcp_ctrl_list);
-static DEFINE_MUTEX(nvme_tcp_ctrl_mutex);
 static struct workqueue_struct *nvme_tcp_wq;
 static const struct blk_mq_ops nvme_tcp_mq_ops;
 static const struct blk_mq_ops nvme_tcp_admin_mq_ops;
@@ -2919,7 +2921,10 @@ static struct nvme_tcp_ctrl *nvme_tcp_alloc_ctrl(struct device *dev,
 	if (!ctrl)
 		return ERR_PTR(-ENOMEM);
 
-	INIT_LIST_HEAD(&ctrl->list);
+	/*
+	 * Safe to init list while allocating ctrl object.
+	 */
+	context_unsafe(INIT_LIST_HEAD(&ctrl->list));
 	ctrl->ctrl.opts = opts;
 	ctrl->ctrl.queue_count = opts->nr_io_queues + opts->nr_write_queues +
 				opts->nr_poll_queues + 1;
-- 
2.53.0