Am 20.04.2016 um 14:13 hat Kevin Wolf geschrieben:
> Am 20.04.2016 um 00:59 hat Max Reitz geschrieben:
> > If the drive's dirty bitmap is dirtied while the mirror operation is
> > running, the cache of the iterator used by the mirror code may become
> > stale and not contain all dirty bits.
> >
> > This only becomes an issue if we are looking for contiguously dirty
> > chunks on the drive. In that case, we can easily detect the discrepancy
> > and just refresh the iterator if one occurs.
> >
> > Signed-off-by: Max Reitz <mre...@redhat.com>
> > ---
> > block/mirror.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/block/mirror.c b/block/mirror.c
> > index 2714a77..9df1fae 100644
> > --- a/block/mirror.c
> > +++ b/block/mirror.c
> > @@ -334,6 +334,11 @@ static uint64_t coroutine_fn
> > mirror_iteration(MirrorBlockJob *s)
> > }
> >
> > hbitmap_next = hbitmap_iter_next(&s->hbi);
> > + if (hbitmap_next > next_sector || hbitmap_next < 0) {
> > + /* The bitmap iterator's cache is stale, refresh it */
> > + bdrv_set_dirty_iter(&s->hbi, next_sector);
> > + hbitmap_next = hbitmap_iter_next(&s->hbi);
> > + }
> > assert(hbitmap_next == next_sector);
>
> The iterator doesn't seem to be used afterwards anyway, so why not just
> use next_sector and stop using the iterator when we already know what
> result we want to get?
And of course I read that code completely wrong because in reality
&s->hbi isn't local. Seems to be the right way to do things then.
Kevin
