io_uring: kill io_cq_unlock()

We're abusing ->completion_lock helpers. io_cq_unlock() neither
locking conditionally nor doing CQE flushing, which means that callers
must have some side reason of taking the lock and should do it directly.

Open code io_cq_unlock() into io_cqring_overflow_kill() and clean it up.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7dabb36856db2b562e78780480396c52c29b2bf4.1687518903.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/io_uring.c

@@ -644,12 +644,6 @@ static inline void io_cq_lock(struct io_ring_ctx *ctx)
 	spin_lock(&ctx->completion_lock);
 }
 
-static inline void io_cq_unlock(struct io_ring_ctx *ctx)
-	__releases(ctx->completion_lock)
-{
-	spin_unlock(&ctx->completion_lock);
-}
-
 /* keep it inlined for io_submit_flush_completions() */
 static inline void __io_cq_unlock_post(struct io_ring_ctx *ctx)
 	__releases(ctx->completion_lock)
@@ -694,10 +688,10 @@ static void io_cqring_overflow_kill(struct io_ring_ctx *ctx)
 	struct io_overflow_cqe *ocqe;
 	LIST_HEAD(list);
 
-	io_cq_lock(ctx);
+	spin_lock(&ctx->completion_lock);
 	list_splice_init(&ctx->cq_overflow_list, &list);
 	clear_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq);
-	io_cq_unlock(ctx);
+	spin_unlock(&ctx->completion_lock);
 
 	while (!list_empty(&list)) {
 		ocqe = list_first_entry(&list, struct io_overflow_cqe, list);