Re: [Qemu-devel] [PATCH for-2.11] qcow2: fix image corruption on commit with persistent snapshot

[Eric Blake]

On 11/17/2017 12:46 PM, Eric Blake wrote:

>>
>> The test fails with -m32 and probably also on Big Endian architectures,
>> because the bitmap hash differs.
> 
> Oh my.  Thanks for the rapid testing.
> 
>> We could "fix" this by replacing the 2100 by a 2102, so for both bit
>> widths rounding is the same.

Actually, thinking about it more, are we sure that a .qcow2 image
created on an -m32 host can be properly loaded on a 64-bit host, despite
their different rounded-up sizes for the bitmaps?  If the difference in
hash is due only to the in-memory representation, but the on-disk layout
is identical, then we are safe; but if the difference in hash is visible
on-disk, then we have a real bug in our qcow2 specification or
implementation of persistent bitmaps.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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