io_uring: enable io_mem_alloc/free to be used in other parts

In preparation for using these helpers, make them non-static and add
them to our internal header.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -2666,7 +2666,7 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 	return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;
 }
 
-static void io_mem_free(void *ptr)
+void io_mem_free(void *ptr)
 {
 	if (!ptr)
 		return;
@@ -2778,7 +2778,7 @@ static void io_rings_free(struct io_ring_ctx *ctx)
 	}
 }
 
-static void *io_mem_alloc(size_t size)
+void *io_mem_alloc(size_t size)
 {
 	gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_NOWARN | __GFP_COMP;
 	void *ret;

io_uring/io_uring.h

@@ -86,6 +86,9 @@ bool __io_alloc_req_refill(struct io_ring_ctx *ctx);
 bool io_match_task_safe(struct io_kiocb *head, struct task_struct *task,
 			bool cancel_all);
 
+void *io_mem_alloc(size_t size);
+void io_mem_free(void *ptr);
+
 #if defined(CONFIG_PROVE_LOCKING)
 static inline void io_lockdep_assert_cq_locked(struct io_ring_ctx *ctx)
 {