linux-kernel - Re: [PATCH 00/13] overlay filesystem v22

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Message-ID: <CAJfpegvQYKHwGh95t2grX4YxZaWd_J+7ZYdHhd0yXn=rKKwkVg@mail.gmail.com>
Date:	Thu, 29 May 2014 13:26:00 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	David Howells <dhowells@...hat.com>
Cc:	"J. R. Okajima" <hooanon05g@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robo Bot <apw@...onical.com>, Felix Fietkau <nbd@...nwrt.org>,
	Neil Brown <neilb@...e.de>,
	Jordi Pujol <jordipujolp@...il.com>, ezk@....cs.sunysb.edu,
	Sedat Dilek <sedat.dilek@...il.com>,
	"mszeredi@...e.cz" <mszeredi@...e.cz>
Subject: Re: [PATCH 00/13] overlay filesystem v22

On Thu, May 29, 2014 at 12:26 PM, David Howells <dhowells@...hat.com> wrote:
> Miklos Szeredi <miklos@...redi.hu> wrote:
>
>> Perfect solution would be an invisible temp directory.  This needs filesystem
>> support, but perhaps not so difficult.  Again could be done later without
>> backward compatibility issues.
>
> Maybe make a tempfile and hardlink it into place when complete.  That's what
> unionmount is doing.

That doesn't work with RENAME_EXCHANGE, which is what overlayfs uses.

I think that's a small price to pay for not needing to add whiteout
support to every single directory operation.

We could also implement RENAME_EXCHANGE with a tmpfile, but then
again, I think that may be too much complexity for too little gain.

Thanks,
Miklos
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