On Thu, Apr 03, 2014 at 03:46:32PM +0200, Kevin Wolf wrote: > If lazy refcounts are enabled for a backing file, committing to this > backing file may leave it in a dirty state even if the commit succeeds. > The reason is that the bdrv_flush() call in bdrv_commit() doesn't flush > refcount updates with lazy refcounts enabled, and qcow2_reopen_prepare() > doesn't take care to flush metadata. > > In order to fix this, this patch also fixes qcow2_mark_clean(), which > contains another ineffective bdrv_flush() call beause lazy refcounts are > disabled only afterwards. All existing callers of qcow2_mark_clean() > either don't modify refcounts or already flush manually, so that this > fixes only a latent, but not yet actually triggerable bug. > > Another instance of the same problem is live snapshots. Again, a real > corruption is prevented by an explicit flush for non-read-only images in > external_snapshot_prepare(), but images using lazy refcounts stay dirty. > > Cc: qemu-sta...@nongnu.org > Signed-off-by: Kevin Wolf <kw...@redhat.com> > --- > block/qcow2.c | 25 +++++++++++++++++++++---- > tests/qemu-iotests/039 | 20 ++++++++++++++++++++ > tests/qemu-iotests/039.out | 11 +++++++++++ > 3 files changed, 52 insertions(+), 4 deletions(-)
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
