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Re: [Qemu-devel] [PATCH] Fix -snapshot deleting images on disk change
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH] Fix -snapshot deleting images on disk change |
Date: |
Mon, 26 Jul 2010 08:58:18 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
Blue Swirl <address@hidden> writes:
> Block device change command did not copy BDRV_O_SNAPSHOT flag. Thus
> the new image did not have this flag and the file got deleted during
> opening.
>
> Fix by copying BDRV_O_SNAPSHOT flag.
Aha: the file gets deleted because bs->is_temporary survives change, but
BDRV_O_SNAPSHOT does not. Thus, the new image gets opened without a
snapshot file wrapped around it. But since is_temporary is still true,
we attempt to delete the (nonexistant) snapshot file, and end up
deleting the image file instead.
Your fix makes sense. But I recommend to additionally set
bs->is_temporary unconditionally in bdrv_open(). Or get rid of it and
test bs->open_flags instead.