Re: [PATCH v4 1/8] fs: move sgid strip operation from inode_init_owner into inode_sgid_strip

["xuyang2018.jy@fujitsu.com" <xuyang2018.jy@fujitsu.com>]

on 2022/4/19 22:05, Christian Brauner wrote:
> On Tue, Apr 19, 2022 at 07:47:07PM +0800, Yang Xu wrote:
>> This has no functional change. Just create and export inode_sgid_strip api for
>> the subsequent patch. This function is used to strip S_ISGID mode when init
>> a new inode.
>>
>> Acked-by: Christian Brauner (Microsoft)<brauner@kernel.org>
>> Signed-off-by: Yang Xu<xuyang2018.jy@fujitsu.com>
>> ---
>>   fs/inode.c         | 22 ++++++++++++++++++----
>>   include/linux/fs.h |  3 ++-
>>   2 files changed, 20 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/inode.c b/fs/inode.c
>> index 9d9b422504d1..3215e61a0021 100644
>> --- a/fs/inode.c
>> +++ b/fs/inode.c
>> @@ -2246,10 +2246,8 @@ void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode,
>>   		/* Directories are special, and always inherit S_ISGID */
>>   		if (S_ISDIR(mode))
>>   			mode |= S_ISGID;
>> -		else if ((mode&  (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)&&
>> -			 !in_group_p(i_gid_into_mnt(mnt_userns, dir))&&
>> -			 !capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID))
>> -			mode&= ~S_ISGID;
>> +		else
>> +			inode_sgid_strip(mnt_userns, dir,&mode);
>>   	} else
>>   		inode_fsgid_set(inode, mnt_userns);
>>   	inode->i_mode = mode;
>> @@ -2405,3 +2403,19 @@ struct timespec64 current_time(struct inode *inode)
>>   	return timestamp_truncate(now, inode);
>>   }
>>   EXPORT_SYMBOL(current_time);
>> +
>> +void inode_sgid_strip(struct user_namespace *mnt_userns,
>> +		      const struct inode *dir, umode_t *mode)
>> +{
>
> I think with Willy agreeing in an earlier version with me and you
> needing to resend anyway I'd say have this return umode_t instead of
> passing a pointer.

IMO, I am fine with your and Willy way. But I need a reason otherwise
I can't convince myself why not use mode pointer directly.

I have asked you and Willy before why return umode_t value is better, 
why not modify mode pointer directly? Since we have use mode as 
argument, why not modify mode pointer directly in function?

Also the function name(inode_sgid_strip and prepare_mode) has  expressed 
their function clearly.