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List:       qemu-devel
Subject:    Re: [Qemu-devel] [RFC PATCH 14/17] block: support FALLOC_FL_PUNCH_HOLE trimming
From:       Chris Wedgwood <cw () f00f ! org>
Date:       2012-03-09 8:35:39
Message-ID: 20120309083539.GA28349 () puku ! stupidest ! org
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> SEEK_HOLE could provide a very simple heuristic to detect preallocated
> files (unfortunately ext4 does not implement SEEK_HOLE yet).

SEEK_HOLE is a weird (confusing and no intuitive) API (IMO).  There is
FIEMAP or whatever it's called which seems somewhat saner.

XFS specific there is also GETBMAP[X].


Simplest still compare the blocks allocated by the file
to it's length (ie. stat.st_blocks != stat.st_size>>9).

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