Am 14.10.2019 um 20:10 hat John Snow geschrieben: > > > On 10/11/19 7:18 PM, John Snow wrote: > > > > > > 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@xxxxxxxxxxxxx> > >>> > >>> 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@xxxxxxxxxxxxx> > >>> Reviewed-by: Max Reitz <mreitz@xxxxxxxxxx> > >>> Message-Id: <20190806152611.280389-1-vsementsov@xxxxxxxxxxxxx> > >>> [Maintainer edit: Max's suggestions from on-list. --js] > >>> Signed-off-by: John Snow <jsnow@xxxxxxxxxx> > >>> --- > >>> 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. > > I've noticed that seasoned C programmers hate extra parentheses a lot. > I've noticed that I cannot remember operator precedence enough to ever > feel like this is actually an improvement. > > Something about a nice weighted tree of ((expr1) || (expr2)) feels > soothing to my weary eyes. So, if it's not terribly important, I'd > prefer to leave it as-is. I don't mind the parentheses, but I do prefer QEMU_IS_ALIGNED() to the open-coded version. Would that be a viable compromise? Kevin -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
