linux-kernel - Re: [PATCH] cgroup: move a check to parse_cgroupfs

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Message-ID: <4EF3F834.0@cn.fujitsu.com>
Date:	Fri, 23 Dec 2011 11:40:36 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>
Subject: Re: [PATCH] cgroup: move a check to parse_cgroupfs_options()

于 2011年12月22日 23:20, Tejun Heo 写道:
> Hello,
> 
> On Thu, Dec 22, 2011 at 04:43:19PM +0800, Li Zefan wrote:
>> Always check the validity of mount options in parse_cgroupfs_options().
>>
>> No functional change.
>>
>> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
>> ---
>>  kernel/cgroup.c |   15 +++++++--------
>>  1 files changed, 7 insertions(+), 8 deletions(-)
>>
>> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
>> index 4936d88..bdb7994 100644
>> --- a/kernel/cgroup.c
>> +++ b/kernel/cgroup.c
>> @@ -1218,7 +1218,6 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
>>  	    (opts->subsys_bits & mask))
>>  		return -EINVAL;
>>  
>> -
>>  	/* Can't specify "none" and some subsystems */
>>  	if (opts->subsys_bits && opts->none)
>>  		return -EINVAL;
>> @@ -1231,6 +1230,13 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
>>  		return -EINVAL;
>>  
>>  	/*
>> +	 * This can happen only when none of the subsystems is enabled
>> +	 * in the system.
>> +	 */
>> +	if (!opts->subsys_bits && !opts->none)
>> +		return -EINVAL;
> 
> The three ifs here share a lot and I think sharing the common parts
> would make the logic clearer.  e.g. The first and this can be easily
> combined to (bool)opts->subsys_bits != (bool)opts->none which would
> explain the logic better too.
> 

ok.

>> @@ -1442,10 +1445,6 @@ static int cgroup_set_super(struct super_block *sb, void *data)
>>  	int ret;
>>  	struct cgroup_sb_opts *opts = data;
>>  
>> -	/* If we don't have a new root, we can't set up a new sb */
>> -	if (!opts->new_root)
>> -		return -EINVAL;
>> -
> 
> And where did this one go?
> 

The other one I removed sets opts->new_root to NULL, and this one detects
the NULL ptr:

if (!opts->subsys_bits && !opts->none)
	return NULL;
...
opts->new_root = NULL;
...
if (!opts->new_root)
	return -EINVAL;

shortcut to:

if (!opts->subsys_bits && !opts->none)
	return -EINVAL;
--
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