io_uring/kbuf: get rid of bl->is_ready

Now that xarray is being exclusively used for the buffer_list lookup,
this check is no longer needed. Get rid of it and the is_ready member.

Cc: stable@vger.kernel.org # v6.4+
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/kbuf.c

@@ -61,7 +61,6 @@ static int io_buffer_add_list(struct io_ring_ctx *ctx,
 	 * always under the ->uring_lock, but the RCU lookup from mmap does.
 	 */
 	bl->bgid = bgid;
-	smp_store_release(&bl->is_ready, 1);
 	return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
 }
 
@@ -721,13 +720,6 @@ void *io_pbuf_get_address(struct io_ring_ctx *ctx, unsigned long bgid)
 
 	if (!bl || !bl->is_mmap)
 		return NULL;
-	/*
-	 * Ensure the list is fully setup. Only strictly needed for RCU lookup
-	 * via mmap, and in that case only for the array indexed groups. For
-	 * the xarray lookups, it's either visible and ready, or not at all.
-	 */
-	if (!smp_load_acquire(&bl->is_ready))
-		return NULL;
 
 	return bl->buf_ring;
 }

io_uring/kbuf.h

@@ -29,8 +29,6 @@ struct io_buffer_list {
 	__u8 is_buf_ring;
 	/* ring mapped provided buffers, but mmap'ed by application */
 	__u8 is_mmap;
-	/* bl is visible from an RCU point of view for lookup */
-	__u8 is_ready;
 };
 
 struct io_buffer {