[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH net 1/4] xen-netback: Fix handling frag_list on grant op error path
On Thu, Jul 17, 2014 at 08:09:49PM +0100, Zoltan Kiss wrote: > The error handling for skb's with frag_list was completely wrong, it caused > double unmap attempts to happen if the error was on the first skb. Move it to > the right place in the loop. > > Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx> > Reported-by: Armin Zentai <armin.zentai@xxxxxxx> > Cc: netdev@xxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx > --- > diff --git a/drivers/net/xen-netback/netback.c > b/drivers/net/xen-netback/netback.c > index 1844a47..604ff71 100644 > --- a/drivers/net/xen-netback/netback.c > +++ b/drivers/net/xen-netback/netback.c > @@ -1030,10 +1030,16 @@ static int xenvif_tx_check_gop(struct xenvif_queue > *queue, > { > struct gnttab_map_grant_ref *gop_map = *gopp_map; > u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx; > + /* This points to the shinfo of the actually checked skb, which could be > + * either the first or the one on the frag_list > + */ I think "checked skb" should be "skb being checked". Feel free to disagree as I'm not native English speaker. :-/ > struct skb_shared_info *shinfo = skb_shinfo(skb); > + /* If this is non-NULL, we are currently checking the frag_list skb, and > + * this points to the shinfo of the first one > + */ > + struct skb_shared_info *first_shinfo = NULL; > int nr_frags = shinfo->nr_frags; > int i, err; > - struct sk_buff *first_skb = NULL; > > /* Check status of header. */ > err = (*gopp_copy)->status; > @@ -1086,31 +1092,28 @@ check_frags: > xenvif_idx_unmap(queue, pending_idx); > } > > + /* And if we found the error while checking the frag_list, unmap > + * the first skb's frags > + */ > + if (first_shinfo) { > + for (j = 0; j < first_shinfo->nr_frags; j++) { > + pending_idx = > frag_get_pending_idx(&first_shinfo->frags[j]); > + xenvif_idx_unmap(queue, pending_idx); > + } > + } > + > /* Remember the error: invalidate all subsequent fragments. */ > err = newerr; > } > > - if (skb_has_frag_list(skb)) { > - first_skb = skb; > - skb = shinfo->frag_list; > - shinfo = skb_shinfo(skb); > + if (skb_has_frag_list(skb) && !first_shinfo) { Will it ever come to the point that we have another skb in this skb's frag list? Is there any reason prevents you from looping over the (possible) subsequent skbs? I guess if the error is deep in the list it's a bit hard to bookkeep... > + first_shinfo = skb_shinfo(skb); > + shinfo = skb_shinfo(skb_shinfo(skb)->frag_list); In that case I would suggest you add BUG_ON(skb_has_frag_list(skb_shinfo(skb)->frag_list)). I think having more nested frag_list should be a bug in current design. Wei. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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