linux-kernel - Re: [PATCH 2/5] proc: use down_read_killable for /proc/pid/smaps

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Date:   Sun, 9 Jun 2019 12:07:36 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Cyrill Gorcunov <gorcunov@...il.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 2/5] proc: use down_read_killable for
 /proc/pid/smaps_rollup



On 17.05.2019 15:45, Michal Hocko wrote:
> On Wed 15-05-19 11:41:14, Konstantin Khlebnikov wrote:
>> Ditto.
> 
> Proper changelog or simply squash those patches into a single patch if
> you do not feel like copy&paste is fun
> 
>>
>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
>> ---
>>   fs/proc/task_mmu.c |    8 ++++++--
>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
>> index 2bf210229daf..781879a91e3b 100644
>> --- a/fs/proc/task_mmu.c
>> +++ b/fs/proc/task_mmu.c
>> @@ -832,7 +832,10 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
>>   
>>   	memset(&mss, 0, sizeof(mss));
>>   
>> -	down_read(&mm->mmap_sem);
>> +	ret = down_read_killable(&mm->mmap_sem);
>> +	if (ret)
>> +		goto out_put_mm;
> 
> Why not ret = -EINTR. The seq_file code seems to be handling all errors
> AFAICS.
> 

I've missed your comment. Sorry.

down_read_killable returns 0 for success and exactly -EINTR for failure.

>> +
>>   	hold_task_mempolicy(priv);
>>   
>>   	for (vma = priv->mm->mmap; vma; vma = vma->vm_next) {
>> @@ -849,8 +852,9 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
>>   
>>   	release_task_mempolicy(priv);
>>   	up_read(&mm->mmap_sem);
>> -	mmput(mm);
>>   
>> +out_put_mm:
>> +	mmput(mm);
>>   out_put_task:
>>   	put_task_struct(priv->task);
>>   	priv->task = NULL;
>