From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49129) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wkupj-0006Aw-Rs for qemu-devel@nongnu.org; Thu, 15 May 2014 08:32:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wkupd-00050S-MP for qemu-devel@nongnu.org; Thu, 15 May 2014 08:32:23 -0400 Received: from lputeaux-656-01-25-125.w80-12.abo.wanadoo.fr ([80.12.84.125]:37684 helo=paradis.irqsave.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wkupd-00050E-DR for qemu-devel@nongnu.org; Thu, 15 May 2014 08:32:17 -0400 Date: Thu, 15 May 2014 14:32:50 +0200 From: =?iso-8859-1?Q?Beno=EEt?= Canet Message-ID: <20140515123250.GI2812@irqsave.net> References: <20140515115859.GF2812@irqsave.net> <20140515120614.GG8452@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20140515120614.GG8452@localhost.localdomain> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH 1/5] 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: =?iso-8859-1?Q?Beno=EEt?= Canet , kwolf@redhat.com, pkrempa@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com The Thursday 15 May 2014 =E0 08:06:14 (-0400), Jeff Cody wrote : > On Thu, May 15, 2014 at 01:58:59PM +0200, Beno=EEt Canet wrote: > > The Wednesday 14 May 2014 =E0 23:20:15 (-0400), Jeff Cody wrote : > > > Currently, node_name is only filled in when done so explicitly by t= he > > > user. If no node_name is specified, then the node name field is no= t > > > populated. > > >=20 > > > If node_names are automatically generated when not specified, that = means > > > that all block job operations can be done by reference to the uniqu= e > > > node_name field. This eliminates ambiguity in filename pathing > > > (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= -name > > > strings: > > > __qemu##00000000IAIYNXXR > > > __qemu##00000002METXTRBQ > > > __qemu##00000001FMBORDWG > > >=20 > > > The prefix is to aid in identifying it as a qemu-generated name, th= e > > > numeric portion is to guarantee uniqueness in a given qemu session,= and > > > the random characters are to further avoid any accidental collision= s > > > with user-specified node-names. > > >=20 > > > 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 c90c71a..81945d3 100644 > > > --- a/block.c > > > +++ b/block.c > > > @@ -838,12 +838,26 @@ 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]; > >=20 > > The room for the '\0' string termination seems to be missing: > >=20 > > char gen_node_name[GEN_NODE_NAME_MAX_LEN + 1]; > > >=20 > The array includes room for it, note the use of 'sizeof()': > #define GEN_NODE_NAME_MAX_LEN (sizeof(GEN_NODE_NAME_PREFIX) + 8 += 8) >=20 > sizeof() includes the '\0' in the length, while strlen() does not; > e.g.: > sizeof("four") =3D 5 > strlen("four") =3D 4 >=20 > > > + static uint32_t counter; /* simple counter to guarantee unique= ness */ > > > + > > > + /* 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'); > > > + } > >=20 > > Is this code generating only 7 random chars instead of 8 ? > >=20 >=20 > It generates 8 random characters (the sample node-name strings in the > commit message were pulled straight from the QMP command > 'query-named-block-nodes') >=20 > > > + gen_node_name[GEN_NODE_NAME_MAX_LEN - 1] =3D '\0'; > >=20 > > Could be: > > gen_node_name[GEN_NODE_NAME_MAX_LEN] =3D '\0'; > > if the array is properly declared. > > >=20 > That would go over the array bounds by 1. Yes I missed the use of sizeof(). I am happy to have learnt that. Sorry for the noise. >=20 > > > + node_name =3D gen_node_name; > > > } > > > =20 > > > /* empty string node name is invalid */ > > > --=20 > > > 1.8.3.1 > > >=20