On 10/15/19 4:44 AM, Kevin Wolf wrote: > 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? > Oh, I'm sorry! I did change that. I didn't mean to appear any more stubborn than I actually am. --js -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
