linux-kernel - Re: [PATCH -next] cgroup/pids: Remove unreachable paths of pids_{can,cancel}

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Message-ID: <56e67b4e-ff00-7405-25c7-0b67d535fa19@huaweicloud.com>
Date: Mon, 5 Aug 2024 08:43:19 +0800
From: Xiu Jianfeng <xiujianfeng@...weicloud.com>
To: Waiman Long <longman@...hat.com>, tj@...nel.org, lizefan.x@...edance.com,
 hannes@...xchg.org, mkoutny@...e.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
 xiujianfeng@...wei.com
Subject: Re: [PATCH -next] cgroup/pids: Remove unreachable paths of
 pids_{can,cancel}_fork



On 2024/8/3 21:59, Waiman Long wrote:
> 
> On 8/3/24 02:16, Xiu Jianfeng wrote:
>> From: Xiu Jianfeng <xiujianfeng@...wei.com>
>>
>> According to the implement of cgroup_css_set_fork() and the usage in
> "implementation"?

Thanks, will do

>> the cpuset controller which also has .can_fork and .cancel_fork hooks,
>> the argument 'cset' for these two hooks must not be NULL, so remove
>> the unrechable paths in thse two hooks.
> 
> It is primarily due to cgroup_css_set_fork() will fail if cset cannot be
> found and the can_fork/cancel_fork method will not be called in this case.

Thanks for your review, I will reword the commit message in the next
version.

> 
> Cheers,
> Longman
> 
>>
>> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>
>> ---
>>   kernel/cgroup/pids.c | 14 ++------------
>>   1 file changed, 2 insertions(+), 12 deletions(-)
>>
>> diff --git a/kernel/cgroup/pids.c b/kernel/cgroup/pids.c
>> index 34aa63d7c9c6..8f61114c36dd 100644
>> --- a/kernel/cgroup/pids.c
>> +++ b/kernel/cgroup/pids.c
>> @@ -272,15 +272,10 @@ static void pids_event(struct pids_cgroup
>> *pids_forking,
>>    */
>>   static int pids_can_fork(struct task_struct *task, struct css_set
>> *cset)
>>   {
>> -    struct cgroup_subsys_state *css;
>>       struct pids_cgroup *pids, *pids_over_limit;
>>       int err;
>>   -    if (cset)
>> -        css = cset->subsys[pids_cgrp_id];
>> -    else
>> -        css = task_css_check(current, pids_cgrp_id, true);
>> -    pids = css_pids(css);
>> +    pids = css_pids(cset->subsys[pids_cgrp_id]);
>>       err = pids_try_charge(pids, 1, &pids_over_limit);
>>       if (err)
>>           pids_event(pids, pids_over_limit);
>> @@ -290,14 +285,9 @@ static int pids_can_fork(struct task_struct
>> *task, struct css_set *cset)
>>     static void pids_cancel_fork(struct task_struct *task, struct
>> css_set *cset)
>>   {
>> -    struct cgroup_subsys_state *css;
>>       struct pids_cgroup *pids;
>>   -    if (cset)
>> -        css = cset->subsys[pids_cgrp_id];
>> -    else
>> -        css = task_css_check(current, pids_cgrp_id, true);
>> -    pids = css_pids(css);
>> +    pids = css_pids(cset->subsys[pids_cgrp_id]);
>>       pids_uncharge(pids, 1);
>>   }
>>