linux-kernel - Re: [PATCH] hugetlb_cgroup: convert comma to semicolon

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Date:   Wed, 19 Aug 2020 10:14:11 +0200
From:   Giuseppe Scrivano <gscrivan@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Xu Wang <vulab@...as.ac.cn>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] hugetlb_cgroup: convert comma to semicolon

Andrew Morton <akpm@...ux-foundation.org> writes:

> On Tue, 18 Aug 2020 06:43:33 +0000 Xu Wang <vulab@...as.ac.cn> wrote:
>
>> Replace a comma between expression statements by a semicolon.
>> 
>> ...
>>
>> --- a/mm/hugetlb_cgroup.c
>> +++ b/mm/hugetlb_cgroup.c
>> @@ -655,7 +655,7 @@ static void __init __hugetlb_cgroup_file_dfl_init(int idx)
>>  	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.events", buf);
>>  	cft->private = MEMFILE_PRIVATE(idx, 0);
>>  	cft->seq_show = hugetlb_events_show;
>> -	cft->file_offset = offsetof(struct hugetlb_cgroup, events_file[idx]),
>> +	cft->file_offset = offsetof(struct hugetlb_cgroup, events_file[idx]);
>>  	cft->flags = CFTYPE_NOT_ON_ROOT;
>>  
>>  	/* Add the events.local file */
>> @@ -664,7 +664,7 @@ static void __init __hugetlb_cgroup_file_dfl_init(int idx)
>>  	cft->private = MEMFILE_PRIVATE(idx, 0);
>>  	cft->seq_show = hugetlb_events_local_show;
>>  	cft->file_offset = offsetof(struct hugetlb_cgroup,
>> -				    events_local_file[idx]),
>> +				    events_local_file[idx]);
>>  	cft->flags = CFTYPE_NOT_ON_ROOT;
>>  
>>  	/* NULL terminate the last cft */
>
> Fixes: faced7e0806cf4 ("mm: hugetlb controller for cgroups v2")

Xu, thanks for spotting it.  Was this code causing any issue or have you
found by inspecting it?

> Wow, why does this code even work.  Presumably the initial value of
> cft->file_offset simply doesn't matter.  Giuseppe, could you please
> check?  We might have some unneeded code in there.

I think in this case having two expressions as part of the same
statement is equivalent to having two separate statements.  Both
cft->file_offset and cft->flags get the expected value.

Regards,
Giuseppe