linux-kernel - Re: [PATCH 27/38] union-mount: In-kernel file copyup routines

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Message-Id: <E1OgfrQ-0000sG-Jx@pomaz-ex.szeredi.hu>
Date:	Wed, 04 Aug 2010 17:26:28 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Valerie Aurora <vaurora@...hat.com>
CC:	viro@...iv.linux.org.uk, miklos@...redi.hu, jblunck@...e.de,
	hch@...radead.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, vaurora@...hat.com,
	Valdis.Kletnieks@...edu
Subject: Re: [PATCH 27/38] union-mount: In-kernel file copyup routines

On Tue, 15 Jun 2010, Valerie Aurora wrote:
> When a file on the read-only layer of a union mount is altered, it
> must be copied up to the topmost read-write layer.  This patch creates
> union_copyup() and its supporting routines.
> 
> Thanks to Valdis Kletnieks for a bug fix.

What happens if there's a crash in the middle of the copyup?

Possible solution is using rename to atomically "replace" the
underlying file.  That however introduces namespace issues: where to
put the temporary file which then needs to be deleted on "fsck.union"?

Miklos
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