virtio_net: fix the missing of the dma cpu sync

Commit 295525e29a5b ("virtio_net: merge dma operations when filling
mergeable buffers") unmaps the buffer with DMA_ATTR_SKIP_CPU_SYNC when
the dma->ref is zero. We do that with DMA_ATTR_SKIP_CPU_SYNC, because we
do not want to do the sync for the entire page_frag. But that misses the
sync for the current area.

This patch does cpu sync regardless of whether the ref is zero or not.

Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable buffers")
Reported-by: Michael Roth <michael.roth@amd.com>
Closes: http://lore.kernel.org/all/20230926130451.axgodaa6tvwqs3ut@amd.com
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index fe7f314d65c971fcad826fa0b3e44a956ef88940..d67f742fbd4c561d4b86ae37fbb62755628870fc 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -607,16 +607,16 @@ static void virtnet_rq_unmap(struct receive_queue *rq, void *buf, u32 len)
 
        --dma->ref;
 
-       if (dma->ref) {
-               if (dma->need_sync && len) {
-                       offset = buf - (head + sizeof(*dma));
+       if (dma->need_sync && len) {
+               offset = buf - (head + sizeof(*dma));
 
-                       virtqueue_dma_sync_single_range_for_cpu(rq->vq, dma->addr, offset,
-                                                               len, DMA_FROM_DEVICE);
-               }
+               virtqueue_dma_sync_single_range_for_cpu(rq->vq, dma->addr,
+                                                       offset, len,
+                                                       DMA_FROM_DEVICE);
+       }
 
+       if (dma->ref)
                return;
-       }
 
        virtqueue_dma_unmap_single_attrs(rq->vq, dma->addr, dma->len,
                                         DMA_FROM_DEVICE, DMA_ATTR_SKIP_CPU_SYNC);