On 02/28/13 at 08:18am, Eric Dumazet wrote:

but.... what is the value of skb_availroom(to) ?

The earlier test at line 2302 should already guard this case ?

               /* Punt if not enough space exists in the first SKB for
                 * the data in the second
                 */
                if (skb->len > skb_availroom(to))
                        break;

Only if it is guaranteed that we never see an MSS > 64K.

Assuming that is true forever, then a21d45726 (tcp: avoid order-1
allocations on wifi and tx path) does in fact resolve this
issue at the cost of not being able to use the extra room
kmalloc() might have given us in __alloc_skb() for collapsing.

Was that an intentional side effect of a21d45726?