From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:48460) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDJcp-0000ld-EK for qemu-devel@nongnu.org; Wed, 06 Mar 2013 14:03:42 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UDJck-0001PY-B7 for qemu-devel@nongnu.org; Wed, 06 Mar 2013 14:03:39 -0500 Received: from ssl.dlhnet.de ([91.198.192.8]:32881 helo=ssl.dlh.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDJck-0001PH-5F for qemu-devel@nongnu.org; Wed, 06 Mar 2013 14:03:34 -0500 Message-ID: <51379304.50307@dlhnet.de> Date: Wed, 06 Mar 2013 20:03:32 +0100 From: Peter Lieven MIME-Version: 1.0 References: <51378200.5010705@dlhnet.de> <513785A0.1010001@redhat.com> <20130306181454.GB3743@localhost.localdomain> <51378B97.2000709@redhat.com> <20130306184800.GB22782@localhost.localdomain> In-Reply-To: <20130306184800.GB22782@localhost.localdomain> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/7] block: only force IO completion in .bdrv_truncate if we are shrinking List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jeff Cody Cc: kwolf@redhat.com, Paolo Bonzini , qemu-devel@nongnu.org, stefanha@redhat.com, sw@weilnetz.de Am 06.03.2013 19:48, schrieb Jeff Cody: > On Wed, Mar 06, 2013 at 07:31:51PM +0100, Paolo Bonzini wrote: >> Il 06/03/2013 19:14, Jeff Cody ha scritto: >>> QCOW breaks with it using a normal raw posix file as a device. As a >>> test: qemu-img create -f qcow test.qcow 5G. Now run qemu with that >>> drive mounted, and try to partition and format it. QEMU now asserts. >>> >>> The nicety of being able to using truncate during a write call, >>> especially for VHDX (which can have relatively large block/cluster >>> sizes), so to grow the file sparsely in a dynamically allocated file. >> >> Perhaps we need two APIs, "truncate" and "revalidate". >> >> Truncate should be a no-op if (!bs->growable). >> >> Revalidate could be called by the block_resize monitor command with no >> size specified. >> >> Paolo > > I think that is a good solution. Is it better to have "truncate" and > "revalidate", or "truncate" and "grow", with grow being a subset of > truncate, with fewer restrictions? There may still be operations > where it is OK to grow a file, but not OK to shrink it. > Or as a first step: a) Call brdv_drain_all() only if the device is shrinked (independently of !bs->growable) b) Call brdv_drain_all() inside iscsi_truncate() because it is a special requirement there c) Fix the value of bs->growable for all drivers Peter