Messages in this thread | | | Subject | Re: [PATCH] Fix guest memory leak and panic | From | Eric Dumazet <> | Date | Tue, 18 Oct 2011 15:20:02 +0200 |
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Le mardi 18 octobre 2011 à 10:47 +0100, Ian Campbell a écrit : > On Tue, 2011-10-18 at 09:36 +0100, Ian Campbell wrote: > > I think the best thing might be to remove the additional ref taking from > > the setter function and audit the previous changes to ensure they > > conform. I'll do that right away and post a fixup patch ASAP. > > Sigh, only one out of the ten callers of (__)skb_frag_set_page expects > skb_frag_set_page to take a new reference. I think that's pretty > comprehensive evidence that the current behaviour is unexpected and > wrong. > > Sorry about this. > > Ian. > > 8<--------------------------------------------------------- > > From 42c26b7ca640bd5cb6f9c3bc76db96c92ed8ff82 Mon Sep 17 00:00:00 2001 > From: Ian Campbell <ian.campbell@citrix.com> > Date: Tue, 18 Oct 2011 09:59:37 +0100 > Subject: [PATCH] net: do not take an additional reference in skb_frag_set_page > > I audited all of the callers in the tree and only one of them (pktgen) expects > it to do so. Taking this reference is pretty obviously confusing and error > prone. > > In particular I looked at the following commits which switched callers of > (__)skb_frag_set_page to the skb paged fragment api: > > 6a930b9f163d7e6d9ef692e05616c4ede65038ec cxgb3: convert to SKB paged frag API. > 5dc3e196ea21e833128d51eb5b788a070fea1f28 myri10ge: convert to SKB paged frag API. > 0e0634d20dd670a89af19af2a686a6cce943ac14 vmxnet3: convert to SKB paged frag API. > 86ee8130a46769f73f8f423f99dbf782a09f9233 virtionet: convert to SKB paged frag API. > 4a22c4c919c201c2a7f4ee09e672435a3072d875 sfc: convert to SKB paged frag API. > 18324d690d6a5028e3c174fc1921447aedead2b8 cassini: convert to SKB paged frag API. > b061b39e3ae18ad75466258cf2116e18fa5bbd80 benet: convert to SKB paged frag API. > b7b6a688d217936459ff5cf1087b2361db952509 bnx2: convert to SKB paged frag API. > 804cf14ea5ceca46554d5801e2817bba8116b7e5 net: xfrm: convert to SKB frag APIs > ea2ab69379a941c6f8884e290fdd28c93936a778 net: convert core to skb paged frag APIs > > Signed-off-by: Ian Campbell <ian.campbell@citrix.com> > --- > include/linux/skbuff.h | 1 - > net/core/pktgen.c | 1 + > 2 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 64f8695..78741da 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -1765,7 +1765,6 @@ static inline void *skb_frag_address_safe(const skb_frag_t *frag) > static inline void __skb_frag_set_page(skb_frag_t *frag, struct page *page) > { > frag->page = page; > - __skb_frag_ref(frag); > } > > /** > diff --git a/net/core/pktgen.c b/net/core/pktgen.c > index 796044a..c4effd4 100644 > --- a/net/core/pktgen.c > +++ b/net/core/pktgen.c > @@ -2603,6 +2603,7 @@ static void pktgen_finalize_skb(struct pktgen_dev *pkt_dev, struct sk_buff *skb, > break; > } > skb_frag_set_page(skb, i, pkt_dev->page); > + skb_frag_ref(skb, i); > skb_shinfo(skb)->frags[i].page_offset = 0; > /*last fragment, fill rest of data*/ > if (i == (frags - 1))
I am ok with this patch, since it makes sense to let driver do the page->_count change itself (it can use a batched add() in case a page is splitted in many frags)
But I suggest using get_page(pkt_dev->page), this seems more obvious to me [ This was how I wrote the thing ;) ]
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