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Date: Thu, 13 Feb 2014 19:56:23 +0100
Message-ID: <CAJfpegvjwHW5=BhvnbTYrnD6SxZwVyNj0tQGciXo_TzYKLANPQ@mail.gmail.com>
Subject: Re: [PATCH 00/13] cross rename v4
From: Miklos Szeredi <miklos@szeredi.hu>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Howells <dhowells@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
        Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
        Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Bruce Fields <bfields@fieldses.org>,
        Christoph Hellwig <hch@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>, Zach Brown <zab@redhat.com>,
        Jan Kara <jack@suse.cz>, Andy Lutomirski <luto@amacapital.net>,
        "mszeredi@suse.cz" <mszeredi@suse.cz>
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On Thu, Feb 13, 2014 at 7:29 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Thu, Feb 13, 2014 at 9:28 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
>>>
>>> I would suggest that whiteouts appear as otherwise negative dentries and that
>>> they don't appear in getdents().
>>
>> I'd argue that this is an administration nightmare.  E.g. what if the
>> a backup needs to be made of the rw layer?
>
> The major issue is user space support.
>
> So what do others that support this do?  Looking at the gitweb for
> ls.c in coreutils, we find:
>
> http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=blob;f=src/ls.c
>
>     # ifdef DT_WHT
>                     case DT_WHT:  type = whiteout;          break;
>     # endif
>
> so that's presumably what we should use.

Fair enough, that allows the thing to be listed, at least.

What about creation?  A new syscall?

Removal?  unlink(2)?

Should stat(2) succeed with a new filetype?

Thanks,
Miklos