Re: [libvirt] [PULL 01/19] util/hbitmap: strict hbitmap_reset

On 10/11/19 4:25 PM, John Snow wrote: > From: Vladimir Sementsov-Ogievskiy <vsementsov(a)virtuozzo.com&gt; > > hbitmap_reset has an unobvious property: it rounds requested region up. > It may provoke bugs, like in recently fixed write-blocking mode of > mirror: user calls reset on unaligned region, not keeping in mind that > there are possible unrelated dirty bytes, covered by rounded-up region > and information of this unrelated "dirtiness" will be lost. > > Make hbitmap_reset strict: assert that arguments are aligned, allowing > only one exception when @start + @count == hb->orig_size. It's needed > to comfort users of hbitmap_next_dirty_area, which cares about > hb->orig_size. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov(a)virtuozzo.com&gt; > Reviewed-by: Max Reitz <mreitz(a)redhat.com&gt; > Message-Id: <20190806152611.280389-1-vsementsov(a)virtuozzo.com&gt; > [Maintainer edit: Max's suggestions from on-list. --js] > Signed-off-by: John Snow <jsnow(a)redhat.com&gt; > --- >   include/qemu/hbitmap.h | 5 +++++ >   tests/test-hbitmap.c   | 2 +- >   util/hbitmap.c         | 4 ++++ >   3 files changed, 10 insertions(+), 1 deletion(-) > > +++ b/util/hbitmap.c > @@ -476,6 +476,10 @@ void hbitmap_reset(HBitmap *hb, uint64_t start, > uint64_t count) >       /* Compute range in the last layer.  */ >       uint64_t first; >       uint64_t last = start + count - 1; > +    uint64_t gran = 1ULL << hb->granularity; > + > +    assert(!(start & (gran - 1))); > +    assert(!(count & (gran - 1)) || (start + count == hb->orig_size)); I know I'm replying a bit late (since this is now a pull request), but would it be worth using the dedicated macro: assert(QEMU_IS_ALIGNED(start, gran)); assert(QEMU_IS_ALIGNED(count, gran) || start + count == hb->orig_size); instead of open-coding it?  (I would also drop the extra () around the right half of ||). If we want it, that would now be a followup patch.