[PATCH net] virtio_net: fix missing dma unmap for resize

[Xuan Zhuo]

For rq, we have three cases getting buffers from virtio core:

1. virtqueue_get_buf{,_ctx}
2. virtqueue_detach_unused_buf
3. callback for virtqueue_resize

But in commit 295525e29a5b("virtio_net: merge dma operations when
filling mergeable buffers"), I missed the dma unmap for the #3 case.

That will leak some memory, because I did not release the pages referred
by the unused buffers.

If we do such script, we will make the system OOM.

    while true
    do
            ethtool -G ens4 rx 128
            ethtool -G ens4 rx 256
            free -m
    done

Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable 
buffers")
Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
---
 drivers/net/virtio_net.c | 43 ++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 21 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index d16f592c2061..6423a3a007ce 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -408,6 +408,17 @@ static struct page *get_a_page(struct receive_queue *rq, 
gfp_t gfp_mask)
        return p;
 }
 
+static void virtnet_rq_free_buf(struct virtnet_info *vi,
+                               struct receive_queue *rq, void *buf)
+{
+       if (vi->mergeable_rx_bufs)
+               put_page(virt_to_head_page(buf));
+       else if (vi->big_packets)
+               give_pages(rq, buf);
+       else
+               put_page(virt_to_head_page(buf));
+}
+
 static void enable_delayed_refill(struct virtnet_info *vi)
 {
        spin_lock_bh(&vi->refill_lock);
@@ -634,17 +645,6 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, 
u32 *len, void **ctx)
        return buf;
 }
 
-static void *virtnet_rq_detach_unused_buf(struct receive_queue *rq)
-{
-       void *buf;
-
-       buf = virtqueue_detach_unused_buf(rq->vq);
-       if (buf && rq->do_dma)
-               virtnet_rq_unmap(rq, buf, 0);
-
-       return buf;
-}
-
 static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 
len)
 {
        struct virtnet_rq_dma *dma;
@@ -1764,7 +1764,7 @@ static void receive_buf(struct virtnet_info *vi, struct 
receive_queue *rq,
        if (unlikely(len < vi->hdr_len + ETH_HLEN)) {
                pr_debug("%s: short packet %i\n", dev->name, len);
                DEV_STATS_INC(dev, rx_length_errors);
-               virtnet_rq_free_unused_buf(rq->vq, buf);
+               virtnet_rq_free_buf(vi, rq, buf);
                return;
        }
 
@@ -4034,14 +4034,15 @@ static void virtnet_sq_free_unused_buf(struct virtqueue 
*vq, void *buf)
 static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf)
 {
        struct virtnet_info *vi = vq->vdev->priv;
+       struct receive_queue *rq;
        int i = vq2rxq(vq);
 
-       if (vi->mergeable_rx_bufs)
-               put_page(virt_to_head_page(buf));
-       else if (vi->big_packets)
-               give_pages(&vi->rq[i], buf);
-       else
-               put_page(virt_to_head_page(buf));
+       rq = &vi->rq[i];
+
+       if (rq->do_dma)
+               virtnet_rq_unmap(rq, buf, 0);
+
+       virtnet_rq_free_buf(vi, rq, buf);
 }
 
 static void free_unused_bufs(struct virtnet_info *vi)
@@ -4057,10 +4058,10 @@ static void free_unused_bufs(struct virtnet_info *vi)
        }
 
        for (i = 0; i < vi->max_queue_pairs; i++) {
-               struct receive_queue *rq = &vi->rq[i];
+               struct virtqueue *vq = vi->rq[i].vq;
 
-               while ((buf = virtnet_rq_detach_unused_buf(rq)) != NULL)
-                       virtnet_rq_free_unused_buf(rq->vq, buf);
+               while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
+                       virtnet_rq_free_unused_buf(vq, buf);
                cond_resched();
        }
 }
-- 
2.32.0.3.g01195cf9f

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