linux-ext4 - Re: the question about ext4 noacl mount option

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Date:   Tue, 31 May 2022 15:03:57 +0000
From:   "xuyang2018.jy@...itsu.com" <xuyang2018.jy@...itsu.com>
To:     Theodore Ts'o <tytso@....edu>
CC:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: the question about ext4 noacl mount option

on 2022/5/31 22:47, Theodore Ts'o wrote:
> On Fri, Apr 15, 2022 at 03:41:32AM +0000, xuyang2018.jy@...itsu.com wrote:
>> Hi Teo
>>
>> When I use mount option noacl on 5.18-rc2, I got the following warning
>>
>> [  179.441511] EXT4-fs: Mount option "noacl" will be removed by 3.5
>>                 Contact linux-ext4@...r.kernel.org if you think we should
>> keep it.
>
> I'm curious... is there a reason why you use noacl?

> That is, if we
> made the noacl mount option a no-op (that is, it wouldn't disable
> Posix ACL's), would it make a difference for your use case?

I don't have use case for this and I use noacl when I wrote a xfstests 
case[1] to verify setgid whether works correctly for my kernel patchset 
that move setgid stripping code into vfs[2].

noacl will affect setgid stripping logic.

The S_ISGID stripping logic is entangled with umask stripping.

If a filesystem doesn't support or enable POSIX ACLs then umask
stripping is done directly in the vfs before calling into the
filesystem.

If the filesystem does support POSIX ACLs then unmask stripping may be
done in the filesystem itself when calling posix_acl_create().

[1]https://patchwork.kernel.org/project/fstests/patch/1653062664-2125-1-git-send-email-xuyang2018.jy@fujitsu.com/
[2]https://patchwork.kernel.org/project/linux-fsdevel/list/?series=643645

>
>        	      	       	    - Ted