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From: Richard Laager <rlaager@wiktel.com>
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Date: Mon, 26 Mar 2012 14:40:47 -0500
Message-ID: <1332790847.3486.26.camel@watermelon.coderich.net>
Mime-Version: 1.0
Subject: Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co,
 aio}_discard for write_zeroes operations
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To: Christoph Hellwig <hch@lst.de>
Cc: qemu-devel@nongnu.org


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On Sat, 2012-03-24 at 16:27 +0100, Christoph Hellwig wrote:
> >         has_discard =3D !fallocate(s->fd, FALLOC_FL_PUNCH_HOLE | FALLOC=
_FL_KEEP_SIZE,
>=20
> There is no point in using FALLOC_FL_KEEP_SIZE together with
> FALLOC_FL_PUNCH_HOLE.

It's *required*. From the man page [0], "The FALLOC_FL_PUNCH_HOLE flag
must be ORed with FALLOC_FL_KEEP_SIZE in mode;"

[0] http://man7.org/linux/man-pages/man2/fallocate.2.html

--=20
Richard

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