linux-kernel - Re: [RFC v6 02/40] vfs: Add MAY_CREATE_FILE and MAY_CREATE

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Date:	Wed, 2 Sep 2015 21:06:32 +0200
From:	Andreas Gruenbacher <agruenba@...hat.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Andreas Gruenbacher <andreas.gruenbacher@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-nfs@...r.kernel.org, linux-api@...r.kernel.org,
	linux-cifs@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [RFC v6 02/40] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR
 permission flags

2015-09-02 20:53 GMT+02:00 J. Bruce Fields <bfields@...ldses.org>:
>> @@ -453,7 +453,8 @@ static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
>>   * this, letting us set arbitrary permissions for filesystem access without
>>   * changing the "normal" UIDs which are used for other things.
>>   *
>> - * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
>> + * When checking for MAY_APPEND, MAY_CREATE_FILE, MAY_CREATE_DIR,
>> + * MAY_WRITE must also be set in @mask.
>
> Why?

So that file systems that don't support MAY_APPEND can ignore the flag
and will then automatically check for MAY_WRITE instead.

> (Also: written as a simple list like that, it's a ambiguous how to
> parse that comment: I think you mean that MAY_WRITE must be set whenever
> MAY_APPEND, MAY_CREATE_FILE, or MAY_CREATE_DIR are set.)

Yes, that's better.

Thanks,
Andreas
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