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Tsirkin" To: Xuan Zhuo Cc: netdev@vger.kernel.org, Jason Wang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , virtualization@lists.linux-foundation.org Subject: Re: [PATCH net] virtio_net: fix missing dma unmap for resize Message-ID: <20231110003406-mutt-send-email-mst@kernel.org> References: <20231106081832.668-1-xuanzhuo@linux.alibaba.com> <20231109070359-mutt-send-email-mst@kernel.org> <1699581525.5133314-4-xuanzhuo@linux.alibaba.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1699581525.5133314-4-xuanzhuo@linux.alibaba.com> On Fri, Nov 10, 2023 at 09:58:45AM +0800, Xuan Zhuo wrote: > On Thu, 9 Nov 2023 07:06:16 -0500, "Michael S. Tsirkin" wrote: > > On Mon, Nov 06, 2023 at 04:18:32PM +0800, Xuan Zhuo wrote: > > > 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 > > > --- > > > 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); > > > } > > > > > > > So we have virtnet_rq_free_buf which sounds like it should free any > > buf, and we have virtnet_rq_free_unused_buf which is only for unused. > > Or so it would seem from names but this is not true. > > Better function names? > > Sorry. not get it. > > virtnet_rq_free_buf() that free the buf passed in. That is called by > virtnet_rq_free_unused_buf or receive_buf to free the buffer. I think > the name is right. > > virtnet_rq_free_unused_buf is called by free_unused_bufs() and the > virtqueue_resize() to free the unused bufs. I think this name is right also. > > So I do not get your mean. > Are there any details I've overlooked? > > Thanks. Bad function names - they are too similar. Function name should say what it does not where it's called from. What is the difference? That virtnet_rq_free_unused_buf unmaps and frees and virtnet_rq_free_buf just frees memory? > > > > > 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 > >