From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49628) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WxFMh-0006qe-HK for qemu-devel@nongnu.org; Wed, 18 Jun 2014 08:53:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WxFMb-0002Sq-CK for qemu-devel@nongnu.org; Wed, 18 Jun 2014 08:53:23 -0400 Received: from lputeaux-656-01-25-125.w80-12.abo.wanadoo.fr ([80.12.84.125]:51525 helo=paradis.irqsave.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WxFMb-0002Si-5X for qemu-devel@nongnu.org; Wed, 18 Jun 2014 08:53:17 -0400 Date: Wed, 18 Jun 2014 14:53:15 +0200 From: =?iso-8859-1?Q?Beno=EEt?= Canet Message-ID: <20140618125315.GA4107@irqsave.net> References: <526da734a5f3cffd2eb56accafdb4add38c75270.1403041699.git.jcody@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <526da734a5f3cffd2eb56accafdb4add38c75270.1403041699.git.jcody@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v6 for 2.1 01/10] block: Auto-generate node_names for each BDS entry List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jeff Cody Cc: kwolf@redhat.com, benoit.canet@irqsave.net, pkrempa@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com The Tuesday 17 Jun 2014 =E0 17:53:49 (-0400), Jeff Cody wrote : > Currently, node_name is only filled in when done so explicitly by the > user. If no node_name is specified, then the node name field is not > populated. >=20 > If node_names are automatically generated when not specified, that mean= s > that all block job operations can be done by reference to the unique > node_name field. This eliminates ambiguity in resolving filenames > (relative filenames, or file descriptors, symlinks, mounts, etc..) that > qemu currently needs to deal with. >=20 > If a node name is specified, then it will not be automatically > generated for that BDS entry. >=20 > If it is automatically generated, it will be prefaced with "__qemu##", > followed by 8 characters of a unique number, followed by 8 random > ASCII characters in the range of 'A-Z'. Some sample generated node-nam= e > strings: > __qemu##00000000IAIYNXXR > __qemu##00000002METXTRBQ > __qemu##00000001FMBORDWG Jeff can't we simply enforce the namespace separation with a check on the= QDict option content ? This way we could be sure that the user can't input a node-name starting = with __qemu. >=20 > The prefix is to aid in identifying it as a qemu-generated name, the > numeric portion is to guarantee uniqueness in a given qemu session, and > the random characters are to further avoid any accidental collisions > with user-specified node-names. >=20 > Reviewed-by: Eric Blake > Signed-off-by: Jeff Cody > --- > block.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) >=20 > diff --git a/block.c b/block.c > index 43abe96..da32bb0 100644 > --- a/block.c > +++ b/block.c > @@ -843,12 +843,26 @@ static int bdrv_open_flags(BlockDriverState *bs, = int flags) > return open_flags; > } > =20 > +#define GEN_NODE_NAME_PREFIX "__qemu##" > +#define GEN_NODE_NAME_MAX_LEN (sizeof(GEN_NODE_NAME_PREFIX) + 8 + 8) > static void bdrv_assign_node_name(BlockDriverState *bs, > const char *node_name, > Error **errp) > { > + char gen_node_name[GEN_NODE_NAME_MAX_LEN]; > + static uint32_t counter; /* simple counter to guarantee uniqueness= */ > + > + /* if node_name is NULL, auto-generate a node name */ > if (!node_name) { > - return; > + int len; > + snprintf(gen_node_name, GEN_NODE_NAME_MAX_LEN, > + "%s%08x", GEN_NODE_NAME_PREFIX, counter++); > + len =3D strlen(gen_node_name); > + while (len < GEN_NODE_NAME_MAX_LEN - 1) { > + gen_node_name[len++] =3D g_random_int_range('A', 'Z'); > + } > + gen_node_name[GEN_NODE_NAME_MAX_LEN - 1] =3D '\0'; > + node_name =3D gen_node_name; > } > =20 > /* empty string node name is invalid */ > --=20 > 1.9.3 >=20