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

On 10/11/19 5:48 PM, Eric Blake wrote: > 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.

> If the PR doesn't make it for some reason, I can amend a cleanup patch for the next PR.