[PATCH 2/4] ublk: mark ublk_queue as const for ublk_register_io_buf

[Uday Shankar <ushankar@purestorage.com>]

In the future, we may allow multiple tasks to operate on one ublk_queue
concurrently. Any writes to ublk_queue in ublk_register_io_buf, which
has no synchronization, would then become data races. Try to ensure that
such writes do not exist by marking ublk_queue pointers as const in
ublk_register_io_buf.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/block/ublk_drv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 57b8625ae64232a750d4f94e76aaf119c28f9450..a617ffde412936d3c37a3ded08a79e3557f4f56f 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -203,7 +203,7 @@ struct ublk_params_header {
 static void ublk_stop_dev_unlocked(struct ublk_device *ub);
 static void ublk_abort_queue(struct ublk_device *ub, struct ublk_queue *ubq);
 static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub,
-		struct ublk_queue *ubq, int tag, size_t offset);
+		const struct ublk_queue *ubq, int tag, size_t offset);
 static inline unsigned int ublk_req_build_flags(struct request *req);
 static inline struct ublksrv_io_desc *ublk_get_iod(struct ublk_queue *ubq,
 						   int tag);
@@ -1918,7 +1918,7 @@ static void ublk_io_release(void *priv)
 }
 
 static int ublk_register_io_buf(struct io_uring_cmd *cmd,
-				struct ublk_queue *ubq, unsigned int tag,
+				const struct ublk_queue *ubq, unsigned int tag,
 				unsigned int index, unsigned int issue_flags)
 {
 	struct ublk_device *ub = cmd->file->private_data;
@@ -2115,7 +2115,7 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 }
 
 static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub,
-		struct ublk_queue *ubq, int tag, size_t offset)
+		const struct ublk_queue *ubq, int tag, size_t offset)
 {
 	struct request *req;
 

-- 
2.34.1