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Re: [Qemu-devel] [RFC PATCH 14/17] block: support FALLOC_FL_PUNCH_HOLE t

From: Paolo Bonzini
Subject: Re: [Qemu-devel] [RFC PATCH 14/17] block: support FALLOC_FL_PUNCH_HOLE trimming
Date: Fri, 09 Mar 2012 09:31:31 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120216 Thunderbird/10.0.1

Il 09/03/2012 09:20, Chris Wedgwood ha scritto:
> for preallocated files this will punch holes all over the place and
> reallocation will cause fragmentation (guests will free and reallocat
> blocks normally)

SEEK_HOLE could provide a very simple heuristic to detect preallocated
files (unfortunately ext4 does not implement SEEK_HOLE yet).

> xfs has a mechanism to convert to unwritten extents that would avoid
> that, but it's not implemented in other filesystems

Interesting, thanks!


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