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. > in this case @count may be not aligned. @start + @count +are With those fixed: Reviewed-by: Max Reitz <mre...@redhat.com> > + * allowed to be greater than hb->orig_size, but only if @start < > hb->orig_size > + * and @start + @count = ALIGN_UP(hb->orig_size, granularity). > */ > void hbitmap_reset(HBitmap *hb, uint64_t start, uint64_t count); > > diff --git a/tests/test-hbitmap.c b/tests/test-hbitmap.c > index 592d8219db..2be56d1597 100644 > --- a/tests/test-hbitmap.c > +++ b/tests/test-hbitmap.c > @@ -423,7 +423,7 @@ static void test_hbitmap_granularity(TestHBitmapData > *data, > hbitmap_test_check(data, 0); > hbitmap_test_set(data, 0, 3); > g_assert_cmpint(hbitmap_count(data->hb), ==, 4); > - hbitmap_test_reset(data, 0, 1); > + hbitmap_test_reset(data, 0, 2); > g_assert_cmpint(hbitmap_count(data->hb), ==, 2); > } > > diff --git a/util/hbitmap.c b/util/hbitmap.c > index bcc0acdc6a..586920cb52 100644 > --- a/util/hbitmap.c > +++ 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)); > > trace_hbitmap_reset(hb, start, count, > start >> hb->granularity, last >> hb->granularity); >
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