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List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Kevin Wolf , Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org, Juan Quintela , libvir-list@redhat.com, Markus Armbruster , "Dr. David Alan Gilbert" , Max Reitz , Stefan Hajnoczi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 10/11/19 5:48 PM, Eric Blake wrote: > On 10/11/19 4:25 PM, John Snow wrote: >> From: Vladimir Sementsov-Ogievskiy >> >> 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 =3D=3D hb->orig_size. It's nee= ded >> to comfort users of hbitmap_next_dirty_area, which cares about >> hb->orig_size. >> >> Signed-off-by: Vladimir Sementsov-Ogievskiy >> Reviewed-by: Max Reitz >> Message-Id: <20190806152611.280389-1-vsementsov@virtuozzo.com> >> [Maintainer edit: Max's suggestions from on-list. --js] >> Signed-off-by: John Snow >> --- >> =C2=A0 include/qemu/hbitmap.h | 5 +++++ >> =C2=A0 tests/test-hbitmap.c=C2=A0=C2=A0 | 2 +- >> =C2=A0 util/hbitmap.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 = | 4 ++++ >> =C2=A0 3 files changed, 10 insertions(+), 1 deletion(-) >> >=20 >> +++ b/util/hbitmap.c >> @@ -476,6 +476,10 @@ void hbitmap_reset(HBitmap *hb, uint64_t start, >> uint64_t count) >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* Compute range in the last layer.=C2=A0= */ >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 uint64_t first; >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 uint64_t last =3D start + count - 1; >> +=C2=A0=C2=A0=C2=A0 uint64_t gran =3D 1ULL << hb->granularity; >> + >> +=C2=A0=C2=A0=C2=A0 assert(!(start & (gran - 1))); >> +=C2=A0=C2=A0=C2=A0 assert(!(count & (gran - 1)) || (start + count =3D= =3D hb->orig_size)); >=20 > I know I'm replying a bit late (since this is now a pull request), but > would it be worth using the dedicated macro: >=20 > assert(QEMU_IS_ALIGNED(start, gran)); > assert(QEMU_IS_ALIGNED(count, gran) || start + count =3D=3D hb->orig_si= ze); >=20 > instead of open-coding it?=C2=A0 (I would also drop the extra () around= the > right half of ||). If we want it, that would now be a followup patch. >=20 If the PR doesn't make it for some reason, I can amend a cleanup patch for the next PR. --js