linux-kernel - Re: [PATCH 1/4] pid: Replace pid bitmap implementation with IDR API

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Message-ID: <CAOCi2DFv-pz_LUZio5gEaJ0mA=y8rG=jUNo=7w-r1Uq2vMLrJw@mail.gmail.com>
Date:   Mon, 25 Sep 2017 23:11:03 +0530
From:   Gargi Sharma <gs051095@...il.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Rik van Riel <riel@...riel.com>,
        Julia Lawall <julia.lawall@...6.fr>, akpm@...ux-foundation.org,
        mingo@...nel.org, pasha.tatashin@...cle.com, ktkhai@...tuozzo.com
Subject: Re: [PATCH 1/4] pid: Replace pid bitmap implementation with IDR API

On Mon, Sep 25, 2017 at 8:29 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 09/25, Gargi Sharma wrote:
>>
>>  void zap_pid_ns_processes(struct pid_namespace *pid_ns)
>>  {
>> -     int nr;
>> +     int nr = 2;
>>       int rc;
>>       struct task_struct *task, *me = current;
>>       int init_pids = thread_group_leader(me) ? 1 : 2;
>> +     struct pid *pid;
>>
>>       /* Don't allow any more processes into the pid namespace */
>>       disable_pid_allocation(pid_ns);
>> @@ -240,8 +230,8 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
>>        *
>>        */
>>       read_lock(&tasklist_lock);
>> -     nr = next_pidmap(pid_ns, 1);
>> -     while (nr > 0) {
>> +     pid = idr_get_next(&pid_ns->idr, &nr);
>> +     while (pid) {
>>               rcu_read_lock();
>>
>>               task = pid_task(find_vpid(nr), PIDTYPE_PID);
>> @@ -250,7 +240,8 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
>>
>>               rcu_read_unlock();
>>
>> -             nr = next_pidmap(pid_ns, nr);
>> +             nr++;
>> +             pid = idr_get_next(&pid_ns->idr, &nr);
>>       }
>>       read_unlock(&tasklist_lock);
>
> Then you should probably rewrite this code using idr_for_each_entry_continue() ?
Yes, I missed this macro in the idr library.
>
> And why do you need find_vpid(nr) if you already have "pid" ?

Thanks for the feedback! Yes, it is not needed anymore and can be removed.

Best,
Gargi
>
> Oleg.
>