[PATCH v4 11/20] nvme: add context annotations for nvme_subsystem::lock

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

Several helpers access or traverse data structures protected by
nvme_subsystem::lock and therefore require callers to hold the lock.
Annotate nvme_mpath_unfreeze(), nvme_mpath_wait_freeze(),
nvme_mpath_start_freeze(), nvme_find_ns_head(), nvme_alloc_ns_head()
and nvme_subsys_check_duplicate_ids() with __must_hold(&subsys->lock)
so that Clang's lock context analysis can validate the locking
requirements at compile time.

Also annotate nvme_subsystem::nsheads and
nvme_ns_head::delayed_removal_secs with __guarded_by(&subsys->lock),
as both are protected by the subsystem lock.

Annotate nvme_init_subsystem() with __context_unsafe(), as it
initializes these lock-protected members before the object is published,
suppressing a false positive from Clang's context analysis.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/host/core.c |  4 ++++
 drivers/nvme/host/nvme.h | 15 ++++++++++-----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index d6a095e1e44e..f7a4cdb988f1 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3274,6 +3274,7 @@ static bool nvme_validate_cntlid(struct nvme_subsystem *subsys,
 }
 
 static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
+	__context_unsafe(/* initialize unpublished/lock-guarded variables */)
 {
 	struct nvme_subsystem *subsys, *found;
 	int ret;
@@ -3845,6 +3846,7 @@ static const struct file_operations nvme_dev_fops = {
 
 static struct nvme_ns_head *nvme_find_ns_head(struct nvme_ctrl *ctrl,
 		unsigned nsid)
+	__must_hold(&ctrl->subsys->lock)
 {
 	struct nvme_ns_head *h;
 
@@ -3867,6 +3869,7 @@ static struct nvme_ns_head *nvme_find_ns_head(struct nvme_ctrl *ctrl,
 
 static int nvme_subsys_check_duplicate_ids(struct nvme_subsystem *subsys,
 		struct nvme_ns_ids *ids)
+	__must_hold(&subsys->lock)
 {
 	bool has_uuid = !uuid_is_null(&ids->uuid);
 	bool has_nguid = memchr_inv(ids->nguid, 0, sizeof(ids->nguid));
@@ -3968,6 +3971,7 @@ static void nvme_add_ns_cdev(struct nvme_ns *ns)
 
 static struct nvme_ns_head *nvme_alloc_ns_head(struct nvme_ctrl *ctrl,
 		struct nvme_ns_info *info)
+	__must_hold(&ctrl->subsys->lock)
 {
 	struct nvme_ns_head *head;
 	size_t size = sizeof(*head);
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 610c685e2263..602d567f3def 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -496,7 +496,8 @@ struct nvme_subsystem {
 	struct list_head	entry;
 	struct mutex		lock;
 	struct list_head	ctrls;
-	struct list_head	nsheads;
+	struct list_head	nsheads
+		__guarded_by(&lock);
 	char			subnqn[NVMF_NQN_SIZE];
 	char			serial[20];
 	char			model[40];
@@ -569,7 +570,8 @@ struct nvme_ns_head {
 	struct mutex		lock;
 	unsigned long		flags;
 	struct delayed_work	remove_work;
-	unsigned int		delayed_removal_secs;
+	unsigned int		delayed_removal_secs
+		__guarded_by(&subsys->lock);
 	atomic_long_t		io_requeue_no_usable_path_count;
 	atomic_long_t		io_fail_no_available_path_count;
 #define NVME_NSHEAD_DISK_LIVE		0
@@ -1041,9 +1043,12 @@ static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
 	return ctrl->ana_log_buf != NULL;
 }
 
-void nvme_mpath_unfreeze(struct nvme_subsystem *subsys);
-void nvme_mpath_wait_freeze(struct nvme_subsystem *subsys);
-void nvme_mpath_start_freeze(struct nvme_subsystem *subsys);
+void nvme_mpath_unfreeze(struct nvme_subsystem *subsys)
+	__must_hold(&subsys->lock);
+void nvme_mpath_wait_freeze(struct nvme_subsystem *subsys)
+	__must_hold(&subsys->lock);
+void nvme_mpath_start_freeze(struct nvme_subsystem *subsys)
+	__must_hold(&subsys->lock);
 void nvme_mpath_default_iopolicy(struct nvme_subsystem *subsys);
 void nvme_failover_req(struct request *req);
 void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl);
-- 
2.53.0