From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57819) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bpnJ9-0000hp-4k for qemu-devel@nongnu.org; Thu, 29 Sep 2016 22:12:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bpnJ8-0003mW-2i for qemu-devel@nongnu.org; Thu, 29 Sep 2016 22:12:15 -0400 Date: Fri, 30 Sep 2016 10:12:05 +0800 From: Fam Zheng Message-ID: <20160930021205.GC29760@lemon> References: <1474974892-5031-1-git-send-email-famz@redhat.com> <20160929124139.GB5916@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160929124139.GB5916@stefanha-x1.localdomain> Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v3] block: Turn on "unmap" in active commit List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Kevin Wolf , qemu-block@nongnu.org, Max Reitz On Thu, 09/29 13:41, Stefan Hajnoczi wrote: > On Tue, Sep 27, 2016 at 07:14:52PM +0800, Fam Zheng wrote: > > We already specified BDRV_O_UNMAP when opening images in 'qemu-img > > commit', but didn't turn on the "unmap" in the active commit job. This > > patch fixes that so that zeroed clusters in top image can be discarded > > which is desired in the virt-sparsify use case, where a temporary > > overlay is created and fstrim'ed before commiting back, to free space in > > the original image. > > > > This also enables it for block-commit. > > > > Signed-off-by: Fam Zheng > > --- > > v3: Change the right parameter. > > v2: Add "unmap" to block-commit as well. [Kevin] > > --- > > block/mirror.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/block/mirror.c b/block/mirror.c > > index f9d1fec..8847ec5 100644 > > --- a/block/mirror.c > > +++ b/block/mirror.c > > @@ -1042,7 +1042,7 @@ void commit_active_start(const char *job_id, BlockDriverState *bs, > > > > mirror_start_job(job_id, bs, base, NULL, speed, 0, 0, > > MIRROR_LEAVE_BACKING_CHAIN, > > - on_error, on_error, false, cb, opaque, &local_err, > > + on_error, on_error, true, cb, opaque, &local_err, > > &commit_active_job_driver, false, base, auto_complete); > > if (local_err) { > > error_propagate(errp, local_err); > > Why is unmap an option at all? > > What's wrong with using BDRV_REQ_MAY_UNMAP on all > blk_aio_pwrite_zeroes() calls? Because unmap is an QMP option of drive-backup. I think in the drive-mirror context, it mitigates the limitation that we have no control over target's BDRV_O_UNMAP (always inherited from source). Fam