On 8/6/19 12:19 PM, Vladimir Sementsov-Ogievskiy wrote: > 06.08.2019 19:09, Max Reitz wrote: >> On 06.08.19 17:26, Vladimir Sementsov-Ogievskiy wrote: >>> 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 <vsement...@virtuozzo.com> >>> --- >>> >>> v2 based on Max's https://github.com/XanClic/qemu.git block >>> which will be merged soon to 4.1, and this patch goes to 4.2 >>> Based-on: https://github.com/XanClic/qemu.git block >>> >>> v1 was "[PATCH] util/hbitmap: fix unaligned reset", and as I understand >>> we all agreed to just assert alignment instead of aligning down >>> automatically. >>> >>> include/qemu/hbitmap.h | 5 +++++ >>> tests/test-hbitmap.c | 2 +- >>> util/hbitmap.c | 4 ++++ >>> 3 files changed, 10 insertions(+), 1 deletion(-) >>> >>> diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h >>> index 4afbe6292e..7865e819ca 100644 >>> --- a/include/qemu/hbitmap.h >>> +++ b/include/qemu/hbitmap.h >>> @@ -132,6 +132,11 @@ void hbitmap_set(HBitmap *hb, uint64_t start, uint64_t >>> count); >>> * @count: Number of bits to reset. >>> * >>> * Reset a consecutive range of bits in an HBitmap. >>> + * @start and @count must be aligned to bitmap granularity. The only >>> exception >>> + * is resetting the tail of the bitmap: @count may be equal to @start + >>> + * hb->orig_size, >> >> s/@start + hb->orig_size/hb->orig_size - @start/, I think. > > Ha, I wanted to say start + count equal to orig_size. Yours is OK too of > course. > >> >>> in this case @count may be not aligned. @start + @count >> >> +are >> >> With those fixed: >> >> Reviewed-by: Max Reitz <mre...@redhat.com> > > Thanks! > I'll add this to the pile for 4.2, after I fix the rebase conflicts that arose from 4.1-rc4. --js
