From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net v2 1/4] net/core: relax BUILD_BUG_ON in netdev_stats_to_stats64 Date: Sat, 30 Jan 2016 10:34:32 -0800 Message-ID: <1454178872.7627.136.camel@edumazet-glaptop2.roam.corp.google.com> References: <1453996188-29965-1-git-send-email-jarod@redhat.com> <1454177982-32870-1-git-send-email-jarod@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, Eric Dumazet , netdev@vger.kernel.org To: Jarod Wilson Return-path: In-Reply-To: <1454177982-32870-1-git-send-email-jarod@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Sat, 2016-01-30 at 13:19 -0500, Jarod Wilson wrote: > The netdev_stats_to_stats64 function copies the deprecated > net_device_stats format stats into rtnl_link_stats64 for legacy support > purposes, but with the BUILD_BUG_ON as it was, it wasn't possible to > extend rtnl_link_stats64 without also extending net_device_stats. Relax > the BUILD_BUG_ON to only require that rtnl_link_stats64 is larger, and > zero out all the stat counters that aren't present in net_device_stats. > > CC: Eric Dumazet > CC: netdev@vger.kernel.org > Signed-off-by: Jarod Wilson > --- > Re-re-sending, hopefully getting the patch to the right list this time. > > net/core/dev.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/net/core/dev.c b/net/core/dev.c > index 8cba3d8..575a7df 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -7253,25 +7253,30 @@ void netdev_run_todo(void) > } > } > > -/* Convert net_device_stats to rtnl_link_stats64. They have the same > - * fields in the same order, with only the type differing. > +/* Convert net_device_stats to rtnl_link_stats64. rtnl_link_stats64 has > + * all the same fields in the same order as net_device_stats, with only > + * the type differing, but rtnl_link_stats64 may have additional fields > + * at the end for newer counters. > */ > void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64, > const struct net_device_stats *netdev_stats) > { > #if BITS_PER_LONG == 64 > - BUILD_BUG_ON(sizeof(*stats64) != sizeof(*netdev_stats)); > + BUILD_BUG_ON(sizeof(*stats64) < sizeof(*netdev_stats)); > memcpy(stats64, netdev_stats, sizeof(*stats64)); > #else > size_t i, n = sizeof(*stats64) / sizeof(u64); > const unsigned long *src = (const unsigned long *)netdev_stats; > u64 *dst = (u64 *)stats64; > > - BUILD_BUG_ON(sizeof(*netdev_stats) / sizeof(unsigned long) != > + BUILD_BUG_ON(sizeof(*netdev_stats) / sizeof(unsigned long) > > sizeof(*stats64) / sizeof(u64)); > for (i = 0; i < n; i++) > dst[i] = src[i]; > #endif > + /* zero out counters that only exist in rtnl_link_stats64 */ > + memset((char *)stats64 + sizeof(*netdev_stats), 0, > + sizeof(*stats64) - sizeof(*netdev_stats)); Are you sure it works on 32bit arches ?