On 1/16/2018 2:08 PM, Cong Wang wrote:
On Sun, Jan 14, 2018 at 9:52 PM, Prashant Bhole
<bhole_prashant...@lab.ntt.co.jp> wrote:
About bug:
During init of clsact/ingress, it links qdisc's cpu_bstats,cpu_qstats
with mini qdisc. TCQ_F_CPUSTATS is set in qdisc->flags during init and
this flag is checked after init to allocate memory for stats.
Hence mini qdisc points to null per-cpu-stats. The problem isn't caught
while updating stats via mini qdisc because per_cpu_ptr(NULL, cpu_num)
or this_cpu_ptr(NULL) gives a valid pointer.
About fix:
Currently stats memory is allocated at two places.
- in qdisc_alloc() if TCQ_F_CPUSTATS is set in Qdisc_ops->static_flags
- in qdisc_create() if TCQ_F_CPUSTATS is set in Qdisc->flags
Qdisc_ops->static_flags is propagated to Qdisc->flags. So to fix this bug,
we set TCQ_F_CPUSTATS in static flags and additional condition to avoid
allocation after init.
Good catch! One nit below.
Fixes: 46209401f8f6 ("net: core: introduce mini_Qdisc and eliminate usage of tp->q
for clsact fastpath")
Signed-off-by: Prashant Bhole <bhole_prashant...@lab.ntt.co.jp>
---
net/sched/sch_api.c | 3 ++-
net/sched/sch_ingress.c | 6 ++----
2 files changed, 4 insertions(+), 5 deletions(-)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 8a04c36e579f..de99a5e80944 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1094,7 +1094,8 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
goto err_out5;
}
- if (qdisc_is_percpu_stats(sch)) {
+ if (!(ops->static_flags & TCQ_F_CPUSTATS) &&
+ qdisc_is_percpu_stats(sch)) {
Instead of checking both flags, it is simpler to just check if sch->cpu_bstats
and sch->cpu_qstats are NULL here?
Also, this patch should go to -net tree, not just net-next, but -net
doesn't have ops->static_flags yet. ;) Given this, consider moving
the sch->cpu_bstats allocation before ops->init(), which might be
simpler.
Cong,
Thanks for reviewing. Based on this patch, Daniel submitted another
patch for -net:
http://patchwork.ozlabs.org/patch/861098/
Let me know if we still need v2 of my patch on -net-next (with your
suggested nit picks).
-Prashant
