From mboxrd@z Thu Jan  1 00:00:00 1970
From: Li Zefan <lizf@cn.fujitsu.com>
Subject: Re: [PATCH] Btrfs: avoid setting ->d_op twice
Date: Wed, 22 Feb 2012 09:29:45 +0800
Message-ID: <4F444509.5000701@cn.fujitsu.com>
References: <4F435E1C.8090902@cn.fujitsu.com> <20120221145229.GI1046@twin.jikos.cz>
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Cc: "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
To: David Sterba <dave@jikos.cz>
Return-path: <linux-btrfs-owner@vger.kernel.org>
In-Reply-To: <20120221145229.GI1046@twin.jikos.cz>
List-ID: <linux-btrfs.vger.kernel.org>

David Sterba wrote:
> Hi,
> 
> thanks for the patch!
> 
> On Tue, Feb 21, 2012 at 05:04:28PM +0800, Li Zefan wrote:
>> Follow those instructions, and you'll trigger a warning in the
>> beginning of d_set_d_op():
>>
>>   # mkfs.btrfs /dev/loop3
>>   # mount /dev/loop3 /mnt
>>   # btrfs sub create /mnt/sub
>>   # btrfs sub snap /mnt /mnt/snap
>>   # touch /mnt/snap/sub
>>   touch: cannot touch `tmp': Permission denied
> 
> is this the right error code? permission denied == EACCESS and this is
> returned in case of file
> 
> (strace touch file)
> 
> open("file", O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK, 0666) = -1 EACCES (Permission denied)
> 
> while mkdir returns (strace mkdir a-dir)
> 
> mkdir("a-dir", 0777)                    = -1 EPERM (Operation not permitted)
> 
> 
> The commands were run as root and EPERM looks more adequate than
> EACCESS.
> 

This is a different issue, and EPERM is returned by VFS not btrfs.

Feel free to submit a patch to fsdevel for discussion.