Date: Tue, 26 Sep 2017 09:30:14 +0800
From: Fam Zheng <famz@redhat.com>
Message-ID: <20170926013014.GB31924@lemon.lan>
References: <20170925145526.32690-1-eblake@redhat.com>
	<20170925145526.32690-19-eblake@redhat.com>
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In-Reply-To: <20170925145526.32690-19-eblake@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v10 18/20] qcow2: Switch
 store_bitmap_data() to byte-based iteration
To: Eric Blake <eblake@redhat.com>
Cc: qemu-devel@nongnu.org, kwolf@redhat.com, jsnow@redhat.com, vsementsov@virtuozzo.com, qemu-block@nongnu.org, Max Reitz <mreitz@redhat.com>

On Mon, 09/25 09:55, Eric Blake wrote:
> Now that we have adjusted the majority of the calls this function
> makes to be byte-based, it is easier to read the code if it makes
> passes over the image using bytes rather than sectors.
> 
> iotests 165 was rather weak - on a default 64k-cluster image, where
> bitmap granularity also defaults to 64k bytes, a single cluster of
> the bitmap table thus covers (64*1024*8) bits which each cover 64k
> bytes, or 32G of image space.  But the test only uses a 1G image,
> so it cannot trigger any more than one loop of the code in
> store_bitmap_data(); and it was writing to the first cluster.  In
> order to test that we are properly aligning which portions of the
> bitmap are being written to the file, we really want to test a case
> where the first dirty bit returned by bdrv_dirty_iter_next() is not
> aligned to the start of a cluster, which we can do by modifying the
> test to write data that doesn't happen to fall in the first cluster
> of the image.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy<vsementsov@virtuozzo.com>

Reviewed-by: Fam Zheng <famz@redhat.com>