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Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?)
From: |
Eric Blake |
Subject: |
Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?) |
Date: |
Fri, 15 Apr 2011 11:24:19 -0600 |
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On 04/15/2011 11:16 AM, Christoph Hellwig wrote:
> On Fri, Apr 15, 2011 at 10:53:48AM +0200, Jim Meyering wrote:
>> Can you or anyone else point to authoritative documentation
>> (or even a summary of those "discussions") of FIEMAP semantics?
>
> A large part of the problem is that there's none and the semantics
> is a hode-podge of random flags that mostly make little sense
> outside of fs developers debugging the layout that we created. The
> closest to a description is Documentation/filesystems/fiemap.txt
> in the kernel tree, but that doesn't document most of the delicate
> points.
Would it be worth borrowing from Solaris' semantics and adding SEEK_HOLE
and SEEK_DATA to lseek(2), as a higher level (less-detailed, but easier
to define and easier to use) interface for discovering the regions of a
file that only contain NUL bytes? FIEMAP is a great interface at
exposing everything possible, but coreutils doesn't necessarily need all
that complexity just for determining when it is safe to skip over a
portion of a file that is either unallocated or unchanged from the
initial 0 contents.
--
Eric Blake address@hidden +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), (continued)
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Jim Meyering, 2011/04/14
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Pádraig Brady, 2011/04/14
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Jim Meyering, 2011/04/14
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Dave Chinner, 2011/04/14
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Pádraig Brady, 2011/04/14
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Dave Chinner, 2011/04/14
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Jim Meyering, 2011/04/15
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Christoph Hellwig, 2011/04/15
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?),
Eric Blake <=
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Christoph Hellwig, 2011/04/15
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Andreas Dilger, 2011/04/15
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Dave Chinner, 2011/04/15
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Andreas Dilger, 2011/04/15
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Dave Chinner, 2011/04/15
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Andreas Dilger, 2011/04/16
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Theodore Tso, 2011/04/16
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Dave Chinner, 2011/04/17
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Andreas Dilger, 2011/04/17
- Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?), Yongqiang Yang, 2011/04/18