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Wed, 8 Apr 2020 11:23:47 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-113-144.ams2.redhat.com [10.36.113.144]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B230F118F24; Wed, 8 Apr 2020 11:23:44 +0000 (UTC) Subject: Re: [PATCH v4 13/30] qcow2: Add QCow2SubclusterType and qcow2_get_subcluster_type() To: Alberto Garcia , qemu-devel@nongnu.org References: From: Max Reitz 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: Wed, 8 Apr 2020 13:23:42 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Mr55Guuft2m0Vu3qUD7DHep7DcOPyj8G2" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: Kevin Wolf , Anton Nefedov , qemu-block@nongnu.org, Vladimir Sementsov-Ogievskiy , "Denis V . Lunev" 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) --Mr55Guuft2m0Vu3qUD7DHep7DcOPyj8G2 Content-Type: multipart/mixed; boundary="zuD3N2n7QF4D8WVnKJpszKkWefGfK4yer" --zuD3N2n7QF4D8WVnKJpszKkWefGfK4yer Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 17.03.20 19:16, Alberto Garcia wrote: > This patch adds QCow2SubclusterType, which is the subcluster-level > version of QCow2ClusterType. All QCOW2_SUBCLUSTER_* values have the > the same meaning as their QCOW2_CLUSTER_* equivalents (when they > exist). See below for details and caveats. >=20 > In images without extended L2 entries clusters are treated as having > exactly one subcluster so it is possible to replace one data type with > the other while keeping the exact same semantics. >=20 > With extended L2 entries there are new possible values, and every > subcluster in the same cluster can obviously have a different > QCow2SubclusterType so functions need to be adapted to work on the > subcluster level. >=20 > There are several things that have to be taken into account: >=20 > a) QCOW2_SUBCLUSTER_COMPRESSED means that the whole cluster is > compressed. We do not support compression at the subcluster > level. >=20 > b) There are two different values for unallocated subclusters: > QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN which means that the whole > cluster is unallocated, and QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC > which means that the cluster is allocated but the subcluster is > not. The latter can only happen in images with extended L2 > entries. >=20 > c) QCOW2_SUBCLUSTER_INVALID is used to detect the cases where an L2 > entry has a value that violates the specification. The caller is > responsible for handling these situations. >=20 > To prevent compatibility problems with images that have invalid > values but are currently being read by QEMU without causing side > effects, QCOW2_SUBCLUSTER_INVALID is only returned for images > with extended L2 entries. >=20 > qcow2_cluster_to_subcluster_type() is added as a separate function > from qcow2_get_subcluster_type(), but this is only temporary and both > will be merged in a subsequent patch. >=20 > Signed-off-by: Alberto Garcia > --- > block/qcow2.h | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 120 insertions(+) >=20 > diff --git a/block/qcow2.h b/block/qcow2.h > index 9611efbc52..52865787ee 100644 > --- a/block/qcow2.h > +++ b/block/qcow2.h [...] > @@ -447,6 +456,33 @@ typedef struct QCowL2Meta > QLIST_ENTRY(QCowL2Meta) next_in_flight; > } QCowL2Meta; > =20 > +/* > + * In images with standard L2 entries all clusters are treated as if > + * they had one subcluster so QCow2ClusterType and QCow2SubclusterType > + * can be mapped to each other and have the exact same meaning > + * (QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC cannot happen in these images). > + * > + * In images with extended L2 entries QCow2ClusterType refers to the > + * complete cluster and QCow2SubclusterType to each of the individual > + * subclusters, so there are several possible combinations: > + * > + * |--------------+---------------------------| > + * | Cluster type | Possible subcluster types | > + * |--------------+---------------------------| > + * | UNALLOCATED | UNALLOCATED_PLAIN | > + * | | ZERO_PLAIN | > + * |--------------+---------------------------| > + * | NORMAL | UNALLOCATED_ALLOC | > + * | | ZERO_ALLOC | > + * | | NORMAL | > + * |--------------+---------------------------| > + * | COMPRESSED | COMPRESSED | > + * |--------------+---------------------------| > + * > + * QCOW2_SUBCLUSTER_INVALID means that the L2 entry is incorrect and > + * the image should be marked corrupt. > + */ > + Oh, a welcome addition! :) [...] > @@ -632,6 +678,80 @@ static inline QCow2ClusterType qcow2_get_cluster_typ= e(BlockDriverState *bs, [...] > +/* > + * In an image without subsclusters @l2_bitmap is ignored and > + * @sc_index must be 0. > + */ > +static inline > +QCow2SubclusterType qcow2_get_subcluster_type(BlockDriverState *bs, > + uint64_t l2_entry, > + uint64_t l2_bitmap, > + unsigned sc_index) > +{ > + BDRVQcow2State *s =3D bs->opaque; > + QCow2ClusterType type =3D qcow2_get_cluster_type(bs, l2_entry); > + assert(sc_index < s->subclusters_per_cluster); > + > + if (has_subclusters(s)) { > + bool sc_zero =3D l2_bitmap & QCOW_OFLAG_SUB_ZERO(sc_index); > + bool sc_alloc =3D l2_bitmap & QCOW_OFLAG_SUB_ALLOC(sc_index); > + switch (type) { > + case QCOW2_CLUSTER_COMPRESSED: > + return QCOW2_SUBCLUSTER_COMPRESSED; Why did you drop the check that l2_bitmap =3D=3D 0 here? Max > + case QCOW2_CLUSTER_ZERO_PLAIN: > + case QCOW2_CLUSTER_ZERO_ALLOC: > + return QCOW2_SUBCLUSTER_INVALID; > + case QCOW2_CLUSTER_NORMAL: > + if (!sc_zero && !sc_alloc) { > + return QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC; > + } else if (!sc_zero && sc_alloc) { > + return QCOW2_SUBCLUSTER_NORMAL; > + } else if (sc_zero && !sc_alloc) { > + return QCOW2_SUBCLUSTER_ZERO_ALLOC; > + } else { /* sc_zero && sc_alloc */ > + return QCOW2_SUBCLUSTER_INVALID; > + } > + case QCOW2_CLUSTER_UNALLOCATED: > + if (!sc_zero && !sc_alloc) { > + return QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN; > + } else if (!sc_zero && sc_alloc) { > + return QCOW2_SUBCLUSTER_INVALID; > + } else if (sc_zero && !sc_alloc) { > + return QCOW2_SUBCLUSTER_ZERO_PLAIN; > + } else { /* sc_zero && sc_alloc */ > + return QCOW2_SUBCLUSTER_INVALID; > + } > + default: > + g_assert_not_reached(); > + } > + } else { > + return qcow2_cluster_to_subcluster_type(type); > + } > +} > + > /* Check whether refcounts are eager or lazy */ > static inline bool qcow2_need_accurate_refcounts(BDRVQcow2State *s) > { >=20 --zuD3N2n7QF4D8WVnKJpszKkWefGfK4yer-- --Mr55Guuft2m0Vu3qUD7DHep7DcOPyj8G2 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl6NtD4ACgkQ9AfbAGHV z0A5wAf8C5sJ6RudqfFMeFGotG63+9ApJ2KYq+metrXdTDdsIgn7d6JErgZk8T06 azYiqAoC35iJ7WBLNOHd36RV1BXuimmdAheshv5R2/l/6GfFFtLcSIQA/bVSDQqE mURxIsu5cAhI2GIR4LjNkZjf42L7vScOIDYLVPI/Ti63anKWcvrt9u3AQem1gzWc iFXsK6ojqieVmDg4o4x48Hfj/bdN30mS6p0BIOWINZL7oa/U+z1BtO2t6j05xYYs fO0D5nrJ28xRESEiiHYksnVPTtcFjygBsbyQMQe9FnlN6XwIsXMvWonvjp8RKuL0 fkgANI0YQ673suQLhCshVyC7AMlWuw== =OmMh -----END PGP SIGNATURE----- --Mr55Guuft2m0Vu3qUD7DHep7DcOPyj8G2--