From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [V2 PATCH 2/9] macvtap: zerocopy: fix truesize underestimation Date: Wed, 16 May 2012 11:04:14 +0800 Message-ID: <4FB3192E.4030803@redhat.com> References: <20120502033901.11782.13157.stgit@amd-6168-8-1.englab.nay.redhat.com> <20120502034144.11782.88947.stgit@amd-6168-8-1.englab.nay.redhat.com> <1337102809.8220.10.camel@oc3660625478.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, mst@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, ebiederm@xmission.com, davem@davemloft.net To: Shirley Ma Return-path: In-Reply-To: <1337102809.8220.10.camel@oc3660625478.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 05/16/2012 01:26 AM, Shirley Ma wrote: > On Wed, 2012-05-02 at 11:41 +0800, Jason Wang wrote: >> As the skb fragment were pinned/built from user pages, we should >> account the page instead of length for truesize. >> >> Signed-off-by: Jason Wang >> --- >> drivers/net/macvtap.c | 6 ++++-- >> 1 files changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c >> index bd4a70d..7cb2684 100644 >> --- a/drivers/net/macvtap.c >> +++ b/drivers/net/macvtap.c >> @@ -519,6 +519,7 @@ static int zerocopy_sg_from_iovec(struct sk_buff >> *skb, const struct iovec *from, >> struct page *page[MAX_SKB_FRAGS]; >> int num_pages; >> unsigned long base; >> + unsigned long truesize; >> >> len = from->iov_len - offset; >> if (!len) { >> @@ -533,10 +534,11 @@ static int zerocopy_sg_from_iovec(struct sk_buff >> *skb, const struct iovec *from, >> (num_pages> MAX_SKB_FRAGS - >> skb_shinfo(skb)->nr_frags)) >> /* put_page is in skb free */ >> return -EFAULT; >> + truesize = size * PAGE_SIZE; > Here should be truesize = size * PAGE_SIZE - offset, right? > We get the whole user page, so need to account them all. Also this is aligned with skb_copy_ubufs(). >> skb->data_len += len; >> skb->len += len; >> - skb->truesize += len; >> - atomic_add(len,&skb->sk->sk_wmem_alloc); >> + skb->truesize += truesize; >> + atomic_add(truesize,&skb->sk->sk_wmem_alloc); >> while (len) { >> int off = base& ~PAGE_MASK; >> int size = min_t(int, len, PAGE_SIZE - off); >> >>