On Thu, 26 Nov 2020 at 17:35, Willem de Bruijn
<willemdebruijn.kernel@xxxxxxxxx> wrote:
> On Thu, Nov 26, 2020 at 3:19 AM Marco Elver <elver@xxxxxxxxxx> wrote:
[...]
> > Will send v2.
>
> Does it make more sense to revert the patch that added the extensions
> and the follow-on fixes and add a separate new patch instead?
That doesn't work, because then we'll end up with a build-broken
commit in between the reverts and the new version, because mac80211
uses skb_get_kcov_handle().
> If adding a new field to the skb, even if only in debug builds,
> please check with pahole how it affects struct layout if you
> haven't yet.
Without KCOV:
/* size: 224, cachelines: 4, members: 72 */
/* sum members: 217, holes: 1, sum holes: 2 */
/* sum bitfield members: 36 bits, bit holes: 2, sum bit holes: 4 bits */
/* forced alignments: 2 */
/* last cacheline: 32 bytes */
With KCOV:
/* size: 232, cachelines: 4, members: 73 */
/* sum members: 225, holes: 1, sum holes: 2 */
/* sum bitfield members: 36 bits, bit holes: 2, sum bit holes: 4 bits */
/* forced alignments: 2 */
/* last cacheline: 40 bytes */
> The skb_extensions idea was mine. Apologies for steering
> this into an apparently unsuccessful direction. Adding new fields
> to skb is very rare because possibly problematic wrt allocation.
