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

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));