[PATCHv2 09/17] nvme: add Clang context annotations for nvme_subsystems_lock

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

The global nvme_subsystems list, nvme_subsystem::entry,
nvme_subsystem::ctrls, and nvme_ctrl::subsys_entry are protected by
nvme_subsystems_lock. Annotate these objects with
__guarded_by(&nvme_subsystems_lock) so that Clang's context analysis
can validate accesses to them.

__nvme_find_get_subsystem() and nvme_validate_cntlid() traverse the
global subsystem list and subsystem controller list and therefore
require callers to hold nvme_subsystems_lock. Annotate both helpers
with __must_hold(&nvme_subsystems_lock).

The initialization of subsys->ctrls in nvme_init_subsystem() occurs
before the subsystem is published and therefore does not require
protection by nvme_subsystems_lock. Annotate the initialization with
context_unsafe() to suppress the corresponding context analysis
warning.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/host/core.c | 11 +++++++++--
 drivers/nvme/host/nvme.h |  6 +++---
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 341753a4be85..89abf94639ff 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -126,7 +126,7 @@ EXPORT_SYMBOL_GPL(nvme_reset_wq);
 struct workqueue_struct *nvme_delete_wq;
 EXPORT_SYMBOL_GPL(nvme_delete_wq);
 
-static LIST_HEAD(nvme_subsystems);
+static __guarded_by(&nvme_subsystems_lock) LIST_HEAD(nvme_subsystems);
 DEFINE_MUTEX(nvme_subsystems_lock);
 
 static DEFINE_IDA(nvme_instance_ida);
@@ -3164,6 +3164,7 @@ static void nvme_put_subsystem(struct nvme_subsystem *subsys)
 }
 
 static struct nvme_subsystem *__nvme_find_get_subsystem(const char *subsysnqn)
+	__must_hold(&nvme_subsystems_lock)
 {
 	struct nvme_subsystem *subsys;
 
@@ -3208,6 +3209,7 @@ static inline bool nvme_is_io_ctrl(struct nvme_ctrl *ctrl)
 
 static bool nvme_validate_cntlid(struct nvme_subsystem *subsys,
 		struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
+	__must_hold(&nvme_subsystems_lock)
 {
 	struct nvme_ctrl *tmp;
 
@@ -3250,7 +3252,12 @@ static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
 	scoped_guard(mutex_init, &subsys->lock)
 		INIT_LIST_HEAD(&subsys->nsheads);
 	kref_init(&subsys->ref);
-	INIT_LIST_HEAD(&subsys->ctrls);
+	/*
+	 * Initializing subsys->ctrls list doesn't need to be protected
+	 * using @nvme_subsystems_lock. So suppress the Clang's warning
+	 * declaring context_unsafe.
+	 */
+	context_unsafe(INIT_LIST_HEAD(&subsys->ctrls));
 	nvme_init_subnqn(subsys, ctrl, id);
 	memcpy(subsys->serial, id->sn, sizeof(subsys->serial));
 	memcpy(subsys->model, id->mn, sizeof(subsys->model));
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index be1467bfae28..837e279bdf01 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -361,7 +361,7 @@ struct nvme_ctrl {
 	wait_queue_head_t state_wq;
 
 	struct nvme_subsystem *subsys;
-	struct list_head subsys_entry;
+	struct list_head subsys_entry __guarded_by(&nvme_subsystems_lock);
 
 	struct opal_dev *opal_dev;
 
@@ -487,9 +487,9 @@ struct nvme_subsystem {
 	 * a separate refcount.
 	 */
 	struct kref		ref;
-	struct list_head	entry;
+	struct list_head	entry __guarded_by(&nvme_subsystems_lock);
 	struct mutex		lock;
-	struct list_head	ctrls;
+	struct list_head	ctrls __guarded_by(&nvme_subsystems_lock);
 	struct list_head	nsheads __guarded_by(&lock);
 	char			subnqn[NVMF_NQN_SIZE];
 	char			serial[20];
-- 
2.53.0