Messages in this thread |  | | Date | Sun, 5 Jun 2022 10:22:26 +0800 (CST) | From | "Chen Lin" <> | Subject | Re:Re: [PATCH v2] net: ethernet: mtk_eth_soc: fix misuse of mem alloc interface netdev[napi]_alloc_frag |
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At 2022-06-03 23:33:25, "Alexander Duyck" <alexander.duyck@gmail.com> wrote: >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.
Thanks for the tips. I'll try again. It can also be seen from here it is easy to make mistakes in parameter fragsz.
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