virtio_net: rx remove premapped failover code

Now, the premapped mode can be enabled unconditionally.

So we can remove the failover code for merge and small mode.
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Larysa Zaremba <larysa.zaremba@intel.com>
Link: https://lore.kernel.org/r/20240511031404.30903-4-xuanzhuo@linux.alibaba.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/virtio_net.c

@@ -348,9 +348,6 @@ struct receive_queue {
 
 	/* Record the last dma info to free after new pages is allocated. */
 	struct virtnet_rq_dma *last_dma;
-
-	/* Do dma by self */
-	bool do_dma;
 };
 
 /* This structure can contain rss message with maximum settings for indirection table and keysize
@@ -850,7 +847,7 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
 	void *buf;
 
 	buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
-	if (buf && rq->do_dma)
+	if (buf)
 		virtnet_rq_unmap(rq, buf, *len);
 
 	return buf;
@@ -863,11 +860,6 @@ static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
 	u32 offset;
 	void *head;
 
-	if (!rq->do_dma) {
-		sg_init_one(rq->sg, buf, len);
-		return;
-	}
-
 	head = page_address(rq->alloc_frag.page);
 
 	offset = buf - head;
@@ -893,7 +885,6 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
 
 	head = page_address(alloc_frag->page);
 
-	if (rq->do_dma) {
 	dma = head;
 
 	/* new pages */
@@ -929,7 +920,6 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
 	}
 
 	++dma->ref;
-	}
 
 	buf = head + alloc_frag->offset;
 
@@ -947,12 +937,9 @@ static void virtnet_rq_set_premapped(struct virtnet_info *vi)
 	if (!vi->mergeable_rx_bufs && vi->big_packets)
 		return;
 
-	for (i = 0; i < vi->max_queue_pairs; i++) {
-		if (virtqueue_set_dma_premapped(vi->rq[i].vq))
-			continue;
-
-		vi->rq[i].do_dma = true;
-	}
+	for (i = 0; i < vi->max_queue_pairs; i++)
+		/* error should never happen */
+		BUG_ON(virtqueue_set_dma_premapped(vi->rq[i].vq));
 }
 
 static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
@@ -2030,7 +2017,6 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
 
 	err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
 	if (err < 0) {
-		if (rq->do_dma)
 		virtnet_rq_unmap(rq, buf, 0);
 		put_page(virt_to_head_page(buf));
 	}
@@ -2145,7 +2131,6 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
 	ctx = mergeable_len_to_ctx(len + room, headroom);
 	err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
 	if (err < 0) {
-		if (rq->do_dma)
 		virtnet_rq_unmap(rq, buf, 0);
 		put_page(virt_to_head_page(buf));
 	}
@@ -5229,7 +5214,7 @@ static void free_receive_page_frags(struct virtnet_info *vi)
 	int i;
 	for (i = 0; i < vi->max_queue_pairs; i++)
 		if (vi->rq[i].alloc_frag.page) {
-			if (vi->rq[i].do_dma && vi->rq[i].last_dma)
+			if (vi->rq[i].last_dma)
 				virtnet_rq_unmap(&vi->rq[i], vi->rq[i].last_dma, 0);
 			put_page(vi->rq[i].alloc_frag.page);
 		}