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Mon, 5 Aug 2019 11:32:44 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.40.205.217]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A559CF6D9; Mon, 5 Aug 2019 11:32:40 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20190802185830.74648-1-vsementsov@virtuozzo.com> From: Max Reitz Openpgp: preference=signencrypt Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: Date: Mon, 5 Aug 2019 13:32:38 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190802185830.74648-1-vsementsov@virtuozzo.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="CAo88kCi4G2kehwymQclYcdlueCCYAHMx" X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Mon, 05 Aug 2019 11:32:44 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH] util/hbitmap: fix unaligned reset X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: fam@euphon.net, kwolf@redhat.com, jsnow@redhat.com, qemu-devel@nongnu.org, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --CAo88kCi4G2kehwymQclYcdlueCCYAHMx Content-Type: multipart/mixed; boundary="3ZzsMiZ55qRtj1XKNibOQPiwmws3SaF7D"; protected-headers="v1" From: Max Reitz To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, jsnow@redhat.com, fam@euphon.net, kwolf@redhat.com, den@openvz.org Message-ID: Subject: Re: [PATCH] util/hbitmap: fix unaligned reset References: <20190802185830.74648-1-vsementsov@virtuozzo.com> In-Reply-To: <20190802185830.74648-1-vsementsov@virtuozzo.com> --3ZzsMiZ55qRtj1XKNibOQPiwmws3SaF7D Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 02.08.19 20:58, Vladimir Sementsov-Ogievskiy wrote: > hbitmap_reset is broken: it rounds up the requested region. It leads to= > the following bug, which is shown by fixed test: >=20 > assume granularity =3D 2 > set(0, 3) # count becomes 4 > reset(0, 1) # count becomes 2 >=20 > But user of the interface assume that virtual bit 1 should be still > dirty, so hbitmap should report count to be 4! >=20 > In other words, because of granularity, when we set one "virtual" bit, > yes, we make all "virtual" bits in same chunk to be dirty. But this > should not be so for reset. >=20 > Fix this, aligning bound correctly. >=20 > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- >=20 > Hi all! >=20 > Hmm, is it a bug or feature? :) > I don't have a test for mirror yet, but I think that sync mirror may be= broken > because of this, as do_sync_target_write() seems to be using unaligned = reset. >=20 > tests/test-hbitmap.c | 2 +- > util/hbitmap.c | 24 +++++++++++++++++++----- > 2 files changed, 20 insertions(+), 6 deletions(-) >=20 > diff --git a/tests/test-hbitmap.c b/tests/test-hbitmap.c > index 592d8219db..0008025a9f 100644 > --- a/tests/test-hbitmap.c > +++ b/tests/test-hbitmap.c > @@ -424,7 +424,7 @@ static void test_hbitmap_granularity(TestHBitmapDat= a *data, > hbitmap_test_set(data, 0, 3); > g_assert_cmpint(hbitmap_count(data->hb), =3D=3D, 4); > hbitmap_test_reset(data, 0, 1); > - g_assert_cmpint(hbitmap_count(data->hb), =3D=3D, 2); > + g_assert_cmpint(hbitmap_count(data->hb), =3D=3D, 4); > } > =20 > static void test_hbitmap_iter_granularity(TestHBitmapData *data, > diff --git a/util/hbitmap.c b/util/hbitmap.c > index 7905212a8b..61a813994a 100644 > --- a/util/hbitmap.c > +++ b/util/hbitmap.c > @@ -473,15 +473,29 @@ void hbitmap_reset(HBitmap *hb, uint64_t start, u= int64_t count) > { > /* Compute range in the last layer. */ > uint64_t first; > - uint64_t last =3D start + count - 1; > + uint64_t last; > + uint64_t end =3D start + count; > + uint64_t gran =3D UINT64_C(1) << hb->granularity; > =20 > - trace_hbitmap_reset(hb, start, count, > - start >> hb->granularity, last >> hb->granular= ity); > + /* > + * We should clear only bits, fully covered by requested region. O= therwise > + * we may clear something that is actually still dirty. > + */ > + first =3D DIV_ROUND_UP(start, gran); > =20 > - first =3D start >> hb->granularity; > - last >>=3D hb->granularity; > + if (end =3D=3D hb->orig_size) { This should be =E2=80=9C>=3D=E2=80=9D. There are callers that don=E2=80=99t make sure that start + count <=3D hb->orig_size (e.g. the backup job just calls it with multiples of cluster_size, which may or may not end up at the image end; and hbitmap_truncate() just uses =E2=80=9Chb->size << hb->granularity=E2=80=9D= as the end, which is arguably not ideal, but that=E2=80=99s how it is). Max > + end =3D DIV_ROUND_UP(end, gran); > + } else { > + end =3D end >> hb->granularity; > + } > + if (end <=3D first) { > + return; > + } > + last =3D end - 1; > assert(last < hb->size); > =20 > + trace_hbitmap_reset(hb, start, count, first, last); > + > hb->count -=3D hb_count_between(hb, first, last); > if (hb_reset_between(hb, HBITMAP_LEVELS - 1, first, last) && > hb->meta) { >=20 --3ZzsMiZ55qRtj1XKNibOQPiwmws3SaF7D-- --CAo88kCi4G2kehwymQclYcdlueCCYAHMx Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl1IE9cACgkQ9AfbAGHV z0An4gf+JO7R2FSizsXWCyLoEhre1yOSvH8muIhgqvBQDYJWFIdU+9jp9RjakhEj lPRVWsujifdBiBVBAVnDyyY3O875LcBW0xXBp3bWO6qTygvGxuOEJwVTJQcC7dtD JFLP2zYp/HUdlD27M13DF+RJxTOgX1sgr6BLGSBkzd7IfQpYnlxWekjZgmUtTEam n+B6sAC/g/HW0SP2CUnPln/b94ntojnEKpupijkw+r0SDhM7Cqp7rmubBT49QjIL RN0Ucd5ko6jknjlb0z/7lDyFzVucm1NREgF5HSh0hRec4Wu5nkd0jWsdTimkdTbE CA2g8nMLDBb1aDlswfcvuf2yhss0Lg== =DAVk -----END PGP SIGNATURE----- --CAo88kCi4G2kehwymQclYcdlueCCYAHMx--