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Re: [Qemu-block] [PATCH v10 18/20] qcow2: Switch store_bitmap_data() to


From: Fam Zheng
Subject: Re: [Qemu-block] [PATCH v10 18/20] qcow2: Switch store_bitmap_data() to byte-based iteration
Date: Tue, 26 Sep 2017 09:30:14 +0800
User-agent: Mutt/1.8.3 (2017-05-23)

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 <address@hidden>
> Reviewed-by: Vladimir Sementsov-Ogievskiy<address@hidden>

Reviewed-by: Fam Zheng <address@hidden>



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