From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: Re: [PATCH 21/62] net: remove the second argument of k[un]map_atomic() Date: Mon, 28 Nov 2011 10:06:03 -0800 Message-ID: <4ED3CD8B.5060000@intel.com> References: <1322371662-26166-1-git-send-email-amwang@redhat.com> <1322371662-26166-22-git-send-email-amwang@redhat.com> <1322381248.2826.1.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Cong Wang , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Jeff Kirsher , Jesse Brandeburg , Bruce Allan , Carolyn Wyborny , Don Skidmore , Greg Rose , Peter P Waskiewicz Jr , John Ronciak , "David S. Miller" , Dean Nelson , Ian Campbell , Jiri Pirko , e1000-devel@lists.sourceforge.net, netdev@vger.kernel.org To: Eric Dumazet Return-path: In-Reply-To: <1322381248.2826.1.camel@edumazet-laptop> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 11/27/2011 12:07 AM, Eric Dumazet wrote: > Le dimanche 27 novembre 2011 =C3=A0 13:27 +0800, Cong Wang a =C3=A9cr= it : >> Signed-off-by: Cong Wang >> --- >> 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 e= 1000_adapter *adapter, >> if (length <=3D copybreak && >> skb_tailroom(skb) >=3D length) { >> u8 *vaddr; >> - vaddr =3D kmap_atomic(buffer_info->page, >> - KM_SKB_DATA_SOFTIRQ); >> + vaddr =3D 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/ne= t/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 =3D kmap_atomic(ps_page->page, KM_SKB_DATA_SOFTIRQ); >> + vaddr =3D 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); >> =20 >> @@ -1465,12 +1465,10 @@ static bool e1000_clean_jumbo_rx_irq(struct = e1000_adapter *adapter, >> if (length <=3D copybreak && >> skb_tailroom(skb) >=3D length) { >> u8 *vaddr; >> - vaddr =3D kmap_atomic(buffer_info->page, >> - KM_SKB_DATA_SOFTIRQ); >> + vaddr =3D 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= =2E 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. I= s that correct? Thanks, Alex