linux-kernel - Re: [PATCH -next 1/3] cgroup/cpuset: Correct invalid remote parition prs

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Message-ID: <ff059171-d38e-41a3-86e0-e092a34ba970@redhat.com>
Date: Sun, 18 Aug 2024 22:18:08 -0400
From: Waiman Long <longman@...hat.com>
To: Chen Ridong <chenridong@...wei.com>, tj@...nel.org,
 lizefan.x@...edance.com, hannes@...xchg.org, adityakali@...gle.com,
 sergeh@...nel.org, mkoutny@...e.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next 1/3] cgroup/cpuset: Correct invalid remote parition
 prs

On 8/18/24 22:14, Waiman Long wrote:
>
> On 8/16/24 04:27, Chen Ridong wrote:
>> When enable a remote partition, I found that:
>>
>> cd /sys/fs/cgroup/
>> mkdir test
>> mkdir test/test1
>> echo +cpuset > cgroup.subtree_control
>> echo +cpuset >  test/cgroup.subtree_control
>> echo 3 > test/test1/cpuset.cpus
>> echo root > test/test1/cpuset.cpus.partition
>> cat test/test1/cpuset.cpus.partition
>> root invalid (Parent is not a partition root)
>>
>> The parent of a remote partition could not be a root. This is due to the
>> emtpy effective_xcpus. It would be better to prompt the message "invalid
>> cpu list in cpuset.cpus.exclusive".
>>
>> Signed-off-by: Chen Ridong <chenridong@...wei.com>
>> ---
>>   kernel/cgroup/cpuset.c | 42 +++++++++++++++++++++++-------------------
>>   1 file changed, 23 insertions(+), 19 deletions(-)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index e34fd6108b06..fdd5346616d3 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -80,6 +80,7 @@ enum prs_errcode {
>>       PERR_HOTPLUG,
>>       PERR_CPUSEMPTY,
>>       PERR_HKEEPING,
>> +    PERR_PMT,

One more thing, the "PMT" acronym for the error code is hard to decode. 
I will suggest you either use the "PERMISSION" or "ACCESS" like the 
EACCESS errno.

Cheers,
Longman

>>   };
>>     static const char * const perr_strings[] = {
>> @@ -91,6 +92,7 @@ static const char * const perr_strings[] = {
>>       [PERR_HOTPLUG]   = "No cpu available due to hotplug",
>>       [PERR_CPUSEMPTY] = "cpuset.cpus and cpuset.cpus.exclusive are 
>> empty",
>>       [PERR_HKEEPING]  = "partition config conflicts with 
>> housekeeping setup",
>> +    [PERR_PMT]       = "Enable partition not permitted",
>>   };
>>     struct cpuset {
>> @@ -1669,7 +1671,7 @@ static int remote_partition_enable(struct 
>> cpuset *cs, int new_prs,
>>        * The user must have sysadmin privilege.
>>        */
>>       if (!capable(CAP_SYS_ADMIN))
>> -        return 0;
>> +        return PERR_PMT;
>>         /*
>>        * The requested exclusive_cpus must not be allocated to other
>> @@ -1683,7 +1685,7 @@ static int remote_partition_enable(struct 
>> cpuset *cs, int new_prs,
>>       if (cpumask_empty(tmp->new_cpus) ||
>>           cpumask_intersects(tmp->new_cpus, subpartitions_cpus) ||
>>           cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))
>> -        return 0;
>> +        return PERR_INVCPUS;
>>         spin_lock_irq(&callback_lock);
>>       isolcpus_updated = partition_xcpus_add(new_prs, NULL, 
>> tmp->new_cpus);
>> @@ -1698,7 +1700,7 @@ static int remote_partition_enable(struct 
>> cpuset *cs, int new_prs,
>>        */
>>       update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
>>       update_sibling_cpumasks(&top_cpuset, NULL, tmp);
>> -    return 1;
>> +    return 0;
>>   }
>
> Since you are changing the meaning of the function returned value, you 
> should also update the return value comment as well.
>
>>     /*
>> @@ -3151,24 +3153,26 @@ static int update_prstate(struct cpuset *cs, 
>> int new_prs)
>>           goto out;
>>         if (!old_prs) {
>> -        enum partition_cmd cmd = (new_prs == PRS_ROOT)
>> -                       ? partcmd_enable : partcmd_enablei;
>> -
>>           /*
>> -         * cpus_allowed and exclusive_cpus cannot be both empty.
>> -         */
>> -        if (xcpus_empty(cs)) {
>> -            err = PERR_CPUSEMPTY;
>> -            goto out;
>> -        }
>> +        * If parent is valid partition, enable local partiion.
>> +        * Otherwise, enable a remote partition.
>> +        */
>> +        if (is_partition_valid(parent)) {
>> +            enum partition_cmd cmd = (new_prs == PRS_ROOT)
>> +                           ? partcmd_enable : partcmd_enablei;
>>   -        err = update_parent_effective_cpumask(cs, cmd, NULL, 
>> &tmpmask);
>> -        /*
>> -         * If an attempt to become local partition root fails,
>> -         * try to become a remote partition root instead.
>> -         */
>> -        if (err && remote_partition_enable(cs, new_prs, &tmpmask))
>> -            err = 0;
>> +            /*
>> +             * cpus_allowed and exclusive_cpus cannot be both empty.
>> +             */
>> +            if (xcpus_empty(cs)) {
>> +                err = PERR_CPUSEMPTY;
>> +                goto out;
>> +            }
>
> The xcpus_empty() check should be done for both local and remote 
> partition.
>
> Cheers,
> Longman
>
>> +
>> +            err = update_parent_effective_cpumask(cs, cmd, NULL, 
>> &tmpmask);
>> +        } else {
>> +            err = remote_partition_enable(cs, new_prs, &tmpmask);
>> +        }
>>       } else if (old_prs && new_prs) {
>>           /*
>>            * A change in load balance state only, no change in cpumasks.