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 <[email protected]>
Reported-by: Armin Zentai <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
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 linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
