[PATCH v4 05/20] nvme: add context annotations for nvme_ns_head::srcu

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

Add Clang lock context annotations for helpers that operate under
head->srcu read-side protection.

The path selection helpers invoked by nvme_find_path() access SRCU-
protected data through srcu_dereference() or list APIs which iterate
through rcu protected list and therefore require the caller to hold
head->srcu. Annotate these helpers and nvme_find_path() with
__must_hold_shared(&head->srcu) so that Clang's lock context analysis
can verify the SRCU locking requirements across the call chain.

Also update nvme_ns_head_ctrl_ioctl() to use __releases_shared()
to match the shared SRCU read-side lock acquired through
srcu_read_lock().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/host/ioctl.c     | 2 +-
 drivers/nvme/host/multipath.c | 6 ++++++
 drivers/nvme/host/nvme.h      | 3 ++-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index 664216eece4a..406e09a79c89 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -692,7 +692,7 @@ int nvme_ns_chr_uring_cmd_iopoll(struct io_uring_cmd *ioucmd,
 static int nvme_ns_head_ctrl_ioctl(struct nvme_ns *ns, unsigned int cmd,
 		void __user *argp, struct nvme_ns_head *head, int srcu_idx,
 		bool open_for_write)
-	__releases(&head->srcu)
+	__releases_shared(&head->srcu)
 {
 	struct nvme_ctrl *ctrl = ns->ctrl;
 	int ret;
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 9b9a657fa330..fd2c2a5b1e33 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -306,6 +306,7 @@ static bool nvme_path_is_disabled(struct nvme_ns *ns)
 }
 
 static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
+	__must_hold_shared(&head->srcu)
 {
 	int found_distance = INT_MAX, fallback_distance = INT_MAX, distance;
 	struct nvme_ns *found = NULL, *fallback = NULL, *ns;
@@ -348,6 +349,7 @@ static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
 
 static struct nvme_ns *nvme_next_ns(struct nvme_ns_head *head,
 		struct nvme_ns *ns)
+	__must_hold_shared(&head->srcu)
 {
 	ns = list_next_or_null_rcu(&head->list, &ns->siblings, struct nvme_ns,
 			siblings);
@@ -357,6 +359,7 @@ static struct nvme_ns *nvme_next_ns(struct nvme_ns_head *head,
 }
 
 static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head)
+	__must_hold_shared(&head->srcu)
 {
 	struct nvme_ns *ns, *found = NULL;
 	int node = numa_node_id();
@@ -405,6 +408,7 @@ static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head)
 }
 
 static struct nvme_ns *nvme_queue_depth_path(struct nvme_ns_head *head)
+	__must_hold_shared(&head->srcu)
 {
 	struct nvme_ns *best_opt = NULL, *best_nonopt = NULL, *ns;
 	unsigned int min_depth_opt = UINT_MAX, min_depth_nonopt = UINT_MAX;
@@ -448,6 +452,7 @@ static inline bool nvme_path_is_optimized(struct nvme_ns *ns)
 }
 
 static struct nvme_ns *nvme_numa_path(struct nvme_ns_head *head)
+	__must_hold_shared(&head->srcu)
 {
 	int node = numa_node_id();
 	struct nvme_ns *ns;
@@ -473,6 +478,7 @@ inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
 }
 
 static bool nvme_available_path(struct nvme_ns_head *head)
+	__must_hold_shared(&head->srcu)
 {
 	struct nvme_ns *ns;
 
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index fba2d7674623..b7c3ba9c0fc1 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -1032,7 +1032,8 @@ extern const struct attribute_group *nvme_dev_attr_groups[];
 extern const struct block_device_operations nvme_bdev_ops;
 
 void nvme_delete_ctrl_sync(struct nvme_ctrl *ctrl);
-struct nvme_ns *nvme_find_path(struct nvme_ns_head *head);
+struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
+	__must_hold_shared(&head->srcu);
 #ifdef CONFIG_NVME_MULTIPATH
 static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
 {
-- 
2.53.0