| Message ID | 1405624192-21722-2-git-send-email-zoltan.kiss@citrix.com |
|---|---|
| State | Superseded, archived |
| Delegated to: | David Miller |
| Headers | show |
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@citrix.com> > Reported-by: Armin Zentai <armin.zentai@ezit.hu> > Cc: netdev@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: xen-devel@lists.xenproject.org > --- > 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. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 18/07/14 16:24, Wei Liu wrote: > 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@citrix.com> >> Reported-by: Armin Zentai <armin.zentai@ezit.hu> >> Cc: netdev@vger.kernel.org >> Cc: linux-kernel@vger.kernel.org >> Cc: xen-devel@lists.xenproject.org >> --- >> 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. There are already 3 things which prevents this - in count_requests we drop the packet if it has more than XEN_NETBK_LEGACY_SLOTS_MAX slots - in get_requests there is a BUG_ON(frag_overflow > MAX_SKB_FRAGS), which shouldn't really due to the prev point - in the same funciont we create a frag_list skb exactly once -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 + */ 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) { + first_shinfo = skb_shinfo(skb); + shinfo = skb_shinfo(skb_shinfo(skb)->frag_list); nr_frags = shinfo->nr_frags; goto check_frags; } - /* There was a mapping error in the frag_list skb. We have to unmap - * the first skb's frags - */ - if (first_skb && err) { - int j; - shinfo = skb_shinfo(first_skb); - for (j = 0; j < shinfo->nr_frags; j++) { - pending_idx = frag_get_pending_idx(&shinfo->frags[j]); - xenvif_idx_unmap(queue, pending_idx); - } - } - *gopp_map = gop_map; return err; }
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@citrix.com> Reported-by: Armin Zentai <armin.zentai@ezit.hu> Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: xen-devel@lists.xenproject.org --- -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html