Re: [PATCH net-next v2 1/1] net/sched: We should only add appropriate qdiscs blocks to ports' xarray

[Jiri Pirko <jiri@resnulli.us>]

Tue, Jan 02, 2024 at 03:06:28PM CET, jhs@mojatatu.com wrote:
>On Tue, Jan 2, 2024 at 4:59 AM Jiri Pirko <jiri@resnulli.us> wrote:
>>
>> The patch subject should briefly describe the nature of the change. Not
>> what "we" should or should not do.
>>
>>
>> Sun, Dec 31, 2023 at 06:23:20PM CET, victor@mojatatu.com wrote:
>> >We should only add qdiscs to the blocks ports' xarray in ingress that
>> >support ingress_block_set/get or in egress that support
>> >egress_block_set/get.
>>
>> Tell the codebase what to do, be imperative. Please read again:
>> https://www.kernel.org/doc/html/v6.6/process/submitting-patches.html#describe-your-changes
>>
>
>We need another rule in the doc on nit-picking which states that we
>need to make progress at some point. We made many changes to this
>patchset based on your suggestions for no other reason other that we
>can progress the discussion. This is a patch that fixes a bug of which
>there are multiple syzbot reports and consumers of the API(last one
>just reported from the MTCP people). There's some sense of urgency to
>apply this patch before the original goes into net. More importantly:
>This patch fixes the issue and follows the same common check which was
>already being done in the committed patchset to check if the qdisc
>supports the block set/get operations.
>
>There are about 3 ways to do this check, you objected to the original,
>we picked something that works fine,  and now you are picking a
>different way with tcf_block. I dont see how tcf_block check would
>help or solve this problem at all given this is a qdisc issue not a
>class issue. What am I missing?

Perhaps I got something wrong, but I thought that the issue is
cl_ops->tcf_block being null for some qdiscs, isn't it?


>
>cheers,
>jamal
>
>> >
>> >Fixes: 913b47d3424e ("net/sched: Introduce tc block netdev tracking infra")
>> >Signed-off-by: Victor Nogueira <victor@mojatatu.com>
>> >Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
>> >Reported-by: Ido Schimmel <idosch@nvidia.com>
>> >Closes: https://lore.kernel.org/all/ZY1hBb8GFwycfgvd@shredder/
>> >Tested-by: Ido Schimmel <idosch@nvidia.com>
>> >Reported-and-tested-by: syzbot+84339b9e7330daae4d66@syzkaller.appspotmail.com
>> >Closes: https://lore.kernel.org/all/0000000000007c85f5060dcc3a28@google.com/
>> >Reported-and-tested-by: syzbot+806b0572c8d06b66b234@syzkaller.appspotmail.com
>> >Closes: https://lore.kernel.org/all/00000000000082f2f2060dcc3a92@google.com/
>> >Reported-and-tested-by: syzbot+0039110f932d438130f9@syzkaller.appspotmail.com
>> >Closes: https://lore.kernel.org/all/0000000000007fbc8c060dcc3a5c@google.com/
>> >---
>> >v1 -> v2:
>> >
>> >- Remove newline between fixes tag and Signed-off-by tag
>> >- Add Ido's Reported-by and Tested-by tags
>> >- Add syzbot's Reported-and-tested-by tags
>> >
>> > net/sched/sch_api.c | 34 ++++++++++++++++++++--------------
>> > 1 file changed, 20 insertions(+), 14 deletions(-)
>> >
>> >diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
>> >index 299086bb6205..426be81276f1 100644
>> >--- a/net/sched/sch_api.c
>> >+++ b/net/sched/sch_api.c
>> >@@ -1187,23 +1187,29 @@ static int qdisc_block_add_dev(struct Qdisc *sch, struct net_device *dev,
>> >       struct tcf_block *block;
>> >       int err;
>> >
>>
>> Why don't you just check cl_ops->tcf_block ?
>> In fact, there could be a helper to do it for you either call the op or
>> return NULL in case it is not defined.
>>
>>
>> >-      block = cl_ops->tcf_block(sch, TC_H_MIN_INGRESS, NULL);
>> >-      if (block) {
>> >-              err = xa_insert(&block->ports, dev->ifindex, dev, GFP_KERNEL);
>> >-              if (err) {
>> >-                      NL_SET_ERR_MSG(extack,
>> >-                                     "ingress block dev insert failed");
>> >-                      return err;
>> >+      if (sch->ops->ingress_block_get) {
>> >+              block = cl_ops->tcf_block(sch, TC_H_MIN_INGRESS, NULL);
>> >+              if (block) {
>> >+                      err = xa_insert(&block->ports, dev->ifindex, dev,
>> >+                                      GFP_KERNEL);
>> >+                      if (err) {
>> >+                              NL_SET_ERR_MSG(extack,
>> >+                                             "ingress block dev insert failed");
>> >+                              return err;
>> >+                      }
>> >               }
>> >       }
>> >
>> >-      block = cl_ops->tcf_block(sch, TC_H_MIN_EGRESS, NULL);
>> >-      if (block) {
>> >-              err = xa_insert(&block->ports, dev->ifindex, dev, GFP_KERNEL);
>> >-              if (err) {
>> >-                      NL_SET_ERR_MSG(extack,
>> >-                                     "Egress block dev insert failed");
>> >-                      goto err_out;
>> >+      if (sch->ops->egress_block_get) {
>> >+              block = cl_ops->tcf_block(sch, TC_H_MIN_EGRESS, NULL);
>> >+              if (block) {
>> >+                      err = xa_insert(&block->ports, dev->ifindex, dev,
>> >+                                      GFP_KERNEL);
>> >+                      if (err) {
>> >+                              NL_SET_ERR_MSG(extack,
>> >+                                             "Egress block dev insert failed");
>> >+                              goto err_out;
>> >+                      }
>> >               }
>> >       }
>> >
>> >--
>> >2.25.1
>> >