linux-ext4 - RE: possible different donor file naming in e4defrag

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Date:	Thu, 11 Sep 2014 15:48:02 -0400
From:	TR Reardon <thomas_reardon@...mail.com>
To:	Andreas Dilger <adilger@...ger.ca>
CC:	"Darrick J. Wong" <darrick.wong@...cle.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: RE: possible different donor file naming in e4defrag

Picking this back up.  How would O_TMPFILE avoid races?  It definitely avoids the unwanted mtime/atime update, but then the existing "<filename>.defrag" pseudo-lock file would no longer be available.  How could you use O_TMPFILE and still avoid multiple defrag?  If this isn't possible, then resetting the parent times on unlink(tmpfile), as you suggest, is the simplest way out of this.

+Reardon

> From: adilger@...ger.ca
> Subject: Re: possible different donor file naming in e4defrag
> Date: Fri, 15 Aug 2014 23:04:21 +0200
> To: thomas_reardon@...mail.com
>
> The reason the donor file is created in the same directory as the source is to try and keep the block allocation policy consistent with the original inode.
>
> You may not need a SIGINT handler, since the timestamp could be reset as soon as the file is created and unlinked.
>
> It may also be possible to use O_TMPFILE on newer kernels to create the donor file to avoid any races?
>
> Cheers, Andreas
>

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