[v1] cgroup/pids: Remove unreachable paths of pids_{can,cancel}_fork

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

Posted by Xiu Jianfeng 1 year, 4 months ago

From: Xiu Jianfeng <xiujianfeng@huawei.com>

According to the implement of cgroup_css_set_fork() and the usage in
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.

Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.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);
 }
 
-- 
2.34.1

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

Posted by Waiman Long 1 year, 4 months ago

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

Cheers,
Longman

>
> Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.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);
>   }
>

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

Posted by Xiu Jianfeng 1 year, 4 months ago


On 2024/8/3 21:59, Waiman Long wrote:
> 
> On 8/3/24 02:16, Xiu Jianfeng wrote:
>> From: Xiu Jianfeng <xiujianfeng@huawei.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@huawei.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);
>>   }
>>