Messages in this thread |  | | From | Alexander Duyck <> | Date | Fri, 3 Jun 2022 08:33:25 -0700 | Subject | Re: [PATCH v2] net: ethernet: mtk_eth_soc: fix misuse of mem alloc interface netdev[napi]_alloc_frag |
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On Fri, Jun 3, 2022 at 8:25 AM Alexander Duyck <alexander.duyck@gmail.com> wrote: > > On Fri, Jun 3, 2022 at 2:03 AM Chen Lin <chen45464546@163.com> wrote: > > > > When rx_flag == MTK_RX_FLAGS_HWLRO, > > rx_data_len = MTK_MAX_LRO_RX_LENGTH(4096 * 3) > PAGE_SIZE. > > netdev_alloc_frag is for alloction of page fragment only. > > Reference to other drivers and Documentation/vm/page_frags.rst > > > > Branch to use alloc_pages when ring->frag_size > PAGE_SIZE. > > > > Signed-off-by: Chen Lin <chen45464546@163.com> > > --- > > drivers/net/ethernet/mediatek/mtk_eth_soc.c | 22 ++++++++++++++++++++-- > > 1 file changed, 20 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c > > index b3b3c07..772d903 100644 > > --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c > > +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c > > @@ -1467,7 +1467,16 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget, > > goto release_desc; > > > > /* alloc new buffer */ > > - new_data = napi_alloc_frag(ring->frag_size); > > + if (ring->frag_size <= PAGE_SIZE) { > > + new_data = napi_alloc_frag(ring->frag_size); > > + } else { > > + struct page *page; > > + unsigned int order = get_order(ring->frag_size); > > + > > + page = alloc_pages(GFP_ATOMIC | __GFP_COMP | > > + __GFP_NOWARN, order); > > + new_data = page ? page_address(page) : NULL; > > + } > > if (unlikely(!new_data)) { > > netdev->stats.rx_dropped++; > > goto release_desc; > > @@ -1914,7 +1923,16 @@ static int mtk_rx_alloc(struct mtk_eth *eth, int ring_no, int rx_flag) > > return -ENOMEM; > > > > for (i = 0; i < rx_dma_size; i++) { > > - ring->data[i] = netdev_alloc_frag(ring->frag_size); > > + if (ring->frag_size <= PAGE_SIZE) { > > + ring->data[i] = netdev_alloc_frag(ring->frag_size); > > + } else { > > + struct page *page; > > + unsigned int order = get_order(ring->frag_size); > > + > > + page = alloc_pages(GFP_KERNEL | __GFP_COMP | > > + __GFP_NOWARN, order); > > + ring->data[i] = page ? page_address(page) : NULL; > > + } > > if (!ring->data[i]) > > return -ENOMEM; > > } > > Actually I looked closer at this driver. Is it able to receive frames > larger than 2K? If not there isn't any point in this change. > > Based on commit 4fd59792097a ("net: ethernet: mediatek: support > setting MTU") it looks like it doesn't, so odds are this patch is not > necessary.
I spoke too soon. I had overlooked the LRO part. With that being the case you can probably optimize this code to do away with the get_order piece entirely, at least during runtime. My main concern is that doing that in the fast-path will be expensive so you would be much better off doing something like get_order(mtk_max_frag_size(MTK_RX_FLAGS_HWLRO)) which would be converted into a constant at compile time since everything else would be less than 1 page in size.
Also you could then replace alloc_pages with __get_free_pages which would take care of the page_address call for you.
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