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Mon, 4 Nov 2019 14:59:00 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.36.118.44]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C5C0719C58; Mon, 4 Nov 2019 14:58:58 +0000 (UTC) Subject: Re: [RFC PATCH v2 14/26] qcow2: Add subcluster support to qcow2_get_cluster_offset() To: Alberto Garcia , qemu-devel@nongnu.org References: <6932c2ddfe19a564cad7c54246290e166525fc46.1572125022.git.berto@igalia.com> 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: <673d72da-bf8c-3ffb-a324-79e93f88a140@redhat.com> Date: Mon, 4 Nov 2019 15:58:57 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <6932c2ddfe19a564cad7c54246290e166525fc46.1572125022.git.berto@igalia.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="v67qdasf4HqgtQPCgwyf2gjP8Vp1Yvw4c" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 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) --v67qdasf4HqgtQPCgwyf2gjP8Vp1Yvw4c Content-Type: multipart/mixed; boundary="yP4GBClMgCRBPHE5l0o8CHqkHKNrlqzT7" --yP4GBClMgCRBPHE5l0o8CHqkHKNrlqzT7 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 26.10.19 23:25, Alberto Garcia wrote: > The logic of this function remains pretty much the same, except that > it uses count_contiguous_subclusters(), which combines the logic of > count_contiguous_clusters() / count_contiguous_clusters_unallocated() > and checks individual subclusters. >=20 > Signed-off-by: Alberto Garcia > --- > block/qcow2-cluster.c | 111 ++++++++++++++++++++---------------------- > 1 file changed, 52 insertions(+), 59 deletions(-) >=20 > diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c > index 990bc070af..e67559152f 100644 > --- a/block/qcow2-cluster.c > +++ b/block/qcow2-cluster.c > @@ -372,66 +372,51 @@ fail: > } > =20 > /* > - * Checks how many clusters in a given L2 slice are contiguous in the im= age > - * file. As soon as one of the flags in the bitmask stop_flags changes c= ompared > - * to the first cluster, the search is stopped and the cluster is not co= unted > - * as contiguous. (This allows it, for example, to stop at the first com= pressed > - * cluster which may require a different handling) > + * Return the number of contiguous subclusters of the exact same type > + * in a given L2 slice, starting from cluster @l2_index, subcluster > + * @sc_index. At most @nb_clusters are checked. Allocated clusters are I=E2=80=99d add a note that reassures that @nb_clusters really is a number = of clusters, not subclusters. (Because if the variable were named =E2=80=9Cx= =E2=80=9D (i.e., it=E2=80=99d be =E2=80=9CAt most @x are checked=E2=80=9D), you=E2=80= =99d assume it refers to a number of subclusters.) OTOH, what I don=E2=80=99t like so far about this series is that the =E2=80= =9Ccluster logic=E2=80=9D is still everywhere when I think it should just be about subclusters now. (Except in few places where it must be about clusters as in something that can have a distinct host offset and/or has an own L2 entry.) So maybe the parameter should really be @nb_subclusters. But I=E2=80=99m not sure. For how this function is written right now, it m= akes sense for it to be @nb_clusters, but I think it could be changed so it would work with @nb_subclusters, too. (Just a single loop over the subclusters and then loading l2_entry+l2_bitmap and checking the offset at every cluster boundary.) > + * also required to be contiguous in the image file. > */ > -static int count_contiguous_clusters(BlockDriverState *bs, int nb_cluste= rs, > - int cluster_size, uint64_t *l2_slice, int l2_index, uint64_t sto= p_flags) > +static int count_contiguous_subclusters(BlockDriverState *bs, int nb_clu= sters, > + unsigned sc_index, uint64_t *l2_= slice, > + int l2_index) > { > BDRVQcow2State *s =3D bs->opaque; > - int i; > - QCow2ClusterType first_cluster_type; > - uint64_t mask =3D stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESS= ED; > - uint64_t first_entry =3D get_l2_entry(s, l2_slice, l2_index); > - uint64_t offset =3D first_entry & mask; > - > - first_cluster_type =3D qcow2_get_cluster_type(bs, first_entry); > - if (first_cluster_type =3D=3D QCOW2_CLUSTER_UNALLOCATED) { > - return 0; > + int i, j, count =3D 0; > + uint64_t l2_entry =3D get_l2_entry(s, l2_slice, l2_index); > + uint64_t l2_bitmap =3D get_l2_bitmap(s, l2_slice, l2_index); > + uint64_t expected_offset =3D l2_entry & L2E_OFFSET_MASK; > + bool check_offset =3D true; > + QCow2ClusterType type =3D > + qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_index); > + > + assert(type !=3D QCOW2_CLUSTER_INVALID); /* The caller should check = this */ > + > + if (type =3D=3D QCOW2_CLUSTER_COMPRESSED) { > + return 1; /* Compressed clusters are always counted one by one *= / Hm, yes, but cluster by cluster, not subcluster by subcluster, so this should be s->subclusters_per_cluster, and perhaps sc_index should be asserted to be 0. (Or it should be s->subclusters_per_cluster - sc_index.) [...] > @@ -514,8 +499,8 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, ui= nt64_t offset, I suppose this is get_subcluster_offset now. [...] > @@ -587,6 +574,13 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, u= int64_t offset, > goto fail; > } > switch (type) { > + case QCOW2_CLUSTER_INVALID: > + qcow2_signal_corruption(bs, true, -1, -1, "Invalid cluster entry= found " > + " (L2 offset: %#" PRIx64 ", L2 index: %#= x)", > + l2_offset, l2_index); > + ret =3D -EIO; > + goto fail; > + break; No need to break here. > case QCOW2_CLUSTER_COMPRESSED: > if (has_data_file(bs)) { > qcow2_signal_corruption(bs, true, -1, -1, "Compressed cluste= r " > @@ -602,16 +596,15 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, = uint64_t offset, > break; Here (QCOW2_CLUSTER_COMPRESSED), c is 1, even though it should count subclusters. Max > case QCOW2_CLUSTER_ZERO_PLAIN: > case QCOW2_CLUSTER_UNALLOCATED: > - /* how many empty clusters ? */ > - c =3D count_contiguous_clusters_unallocated(bs, nb_clusters, > - l2_slice, l2_index, ty= pe); > + c =3D count_contiguous_subclusters(bs, nb_clusters, sc_index, > + l2_slice, l2_index); > *cluster_offset =3D 0; > break; --yP4GBClMgCRBPHE5l0o8CHqkHKNrlqzT7-- --v67qdasf4HqgtQPCgwyf2gjP8Vp1Yvw4c Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl3APLEACgkQ9AfbAGHV z0CQnQgAgTWcl6HpUNx8k/y4uS3QUGUWaCRZmlr4riqJFGejYPxJR8jAVO7BkbqQ g/ZWcJnDa4yYrivtZKrx1dzAS8tMD+w+97eJqImP49aFBxtS3NtQcS+mDgtyklAP qdyA12J0ZnVH3sOh8rt9ZNao3yUk415da2yo5MrUX5V2kgMjaAYzoDytu2ICAcnQ 4W6D/oMwgDzmMbL3u4bHvk80IlD6gllmJsUXpZuiKeigei7mQ2sW4DLU8Ga7FO8L l4GZZ78pOgyBpASSUEB//QBSKSJMPVlL7FNm5MNR7gXwhcnW+Jr7B/JW5Pl/P4oX Bi+LhR6kgtI/9Rk/sAHcjfLdojBNrw== =sacI -----END PGP SIGNATURE----- --v67qdasf4HqgtQPCgwyf2gjP8Vp1Yvw4c--