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! > >> + * 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); >> > > -- Best regards, Vladimir