Messages in this thread | | | Date | Mon, 28 Nov 2011 10:06:03 -0800 | From | Alexander Duyck <> | Subject | Re: [PATCH 21/62] net: remove the second argument of k[un]map_atomic() |
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On 11/27/2011 12:07 AM, Eric Dumazet wrote: > Le dimanche 27 novembre 2011 à 13:27 +0800, Cong Wang a écrit : >> Signed-off-by: Cong Wang <amwang@redhat.com> >> --- >> diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c >> index cf480b5..b194beb 100644 >> --- a/drivers/net/ethernet/intel/e1000/e1000_main.c >> +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c >> @@ -3878,11 +3878,9 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_adapter *adapter, >> if (length <= copybreak && >> skb_tailroom(skb) >= length) { >> u8 *vaddr; >> - vaddr = kmap_atomic(buffer_info->page, >> - KM_SKB_DATA_SOFTIRQ); >> + vaddr = kmap_atomic(buffer_info->page); >> memcpy(skb_tail_pointer(skb), vaddr, length); >> - kunmap_atomic(vaddr, >> - KM_SKB_DATA_SOFTIRQ); >> + kunmap_atomic(vaddr); >> /* re-use the page, so don't erase >> * buffer_info->page */ >> skb_put(skb, length); >> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c >> index a855db1..8603c87 100644 >> --- a/drivers/net/ethernet/intel/e1000e/netdev.c >> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c >> @@ -1272,9 +1272,9 @@ static bool e1000_clean_rx_irq_ps(struct e1000_adapter *adapter, >> */ >> dma_sync_single_for_cpu(&pdev->dev, ps_page->dma, >> PAGE_SIZE, DMA_FROM_DEVICE); >> - vaddr = kmap_atomic(ps_page->page, KM_SKB_DATA_SOFTIRQ); >> + vaddr = kmap_atomic(ps_page->page); >> memcpy(skb_tail_pointer(skb), vaddr, l1); >> - kunmap_atomic(vaddr, KM_SKB_DATA_SOFTIRQ); >> + kunmap_atomic(vaddr); >> dma_sync_single_for_device(&pdev->dev, ps_page->dma, >> PAGE_SIZE, DMA_FROM_DEVICE); >> >> @@ -1465,12 +1465,10 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_adapter *adapter, >> if (length <= copybreak && >> skb_tailroom(skb) >= length) { >> u8 *vaddr; >> - vaddr = kmap_atomic(buffer_info->page, >> - KM_SKB_DATA_SOFTIRQ); >> + vaddr = kmap_atomic(buffer_info->page); >> memcpy(skb_tail_pointer(skb), vaddr, >> length); >> - kunmap_atomic(vaddr, >> - KM_SKB_DATA_SOFTIRQ); >> + kunmap_atomic(vaddr); >> /* re-use the page, so don't erase >> * buffer_info->page */ >> skb_put(skb, length); > But why are these drivers using kmap_atomic() in first place, since > their fragments are allocated in regular zone (GFP_ATOMIC or > GFP_KERNEL) ?
I was asking the same thing myself recently when I started working on some copy-break like code for the ixgbe driver. I believe the main reason is a lack of documentation. This code is based loosely on the skb_copy_bits code which will use kmap_skb_frag over all of the paged portions of the sk_buff. As such it was decided to map things via kmap_atomic in order to guarantee the pages had a valid virtual address.
If I understand things correctly, what you are brining up is that pages allocated with either GFP_ATOMIC or GFP_KERNEL will always be allocated from the lowmem pool and as such page_address should always succeed. Is that correct?
Thanks,
Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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