Date: Tue, 26 Apr 2011 10:02:22 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Alexander Motin <mav@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, "Bjoern A. Zeeb" <bz@freebsd.org>, Robert Watson <rwatson@freebsd.org>, svn-src-head@freebsd.org, Warner Losh <imp@bsdimp.com> Subject: Re: svn commit: r220982 - in head: . sys/amd64/conf sys/arm/conf sys/conf sys/i386/conf sys/ia64/conf sys/mips/conf sys/mips/malta sys/pc98/conf sys/powerpc/conf sys/sparc64/conf sys/sun4v/conf Message-ID: <20110426080222.GG2472@garage.freebsd.pl> In-Reply-To: <4DB67939.6080301@FreeBSD.org> References: <CD028561-B550-4896-BE65-7C827BE6A34A@FreeBSD.org> <20110425134531.GA4391@garage.freebsd.pl> <50385B7B-7EC8-4BC3-8F88-83F9EB4096FB@bsdimp.com> <4DB5A166.9010302@FreeBSD.org> <67F62848-FAA3-4C46-A95A-DA7C82281898@bsdimp.com> <4DB5B0A9.4030805@FreeBSD.org> <20110426070020.GC2472@garage.freebsd.pl> <4DB6721B.3020600@FreeBSD.org> <20110426073517.GF2472@garage.freebsd.pl> <4DB67939.6080301@FreeBSD.org>
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On Tue, Apr 26, 2011 at 10:50:17AM +0300, Alexander Motin wrote:
> On 26.04.2011 10:35, Pawel Jakub Dawidek wrote:
> >On Tue, Apr 26, 2011 at 10:19:55AM +0300, Alexander Motin wrote:
> >>On 26.04.2011 10:00, Pawel Jakub Dawidek wrote:
> >>>On Mon, Apr 25, 2011 at 08:34:33PM +0300, Alexander Motin wrote:
> >>>>I've thought about the process of fixing hardcoded provider names the=
re,
> >>>>and it is absolutely not trivial. If we take the "symlinking" way (pa=
tch
> >>>>is already posted to current@), I think it will be much easier for
> >>>>everybody, and especially users, if I hack all mentioned above GEOM
> >>>>classes to ignore adX/adaY difference in provider names. And it should
> >>>>perfectly fit into remaining time window.
> >>>
> >>>Could you be more specific what the hack would do exactly?
> >>
> >>I would write some comparison function, which would search both
> >>names for adX/adaY prefixes, if they found on both arguments,
> >>trimmed them and compared remaining parts.
> >>
> >>I think for usual purpose of name hardcoding device name part is
> >>less important. Comparing partition names part should be enough. The
> >>tricky part there is to properly identify device part, so I was
> >>thinking about specific hack for adX/adaY.
> >
> >I was wondering how would you match X and Y, but this is indeed not
> >important. So on taste we could do (totally untested):
> >
> >static bool
> >provider_name_matches(const char *ppname, const char *hcname)
> >{
> >
> > if (strcmp(ppname, hcname) =3D=3D 0)
> > return (true);
> > if (strncmp(hcname, "ad", 2) !=3D 0 ||
> > hcname[2]< '0' || hcname[2]> '9') {
> > return (false);
> > }
> > if (strncmp(ppname, "ada", 3) !=3D 0 ||
> > ppname[3]< '0' || ppname[3]> '9') {
> > return (false);
> > }
> > /* Skip 'ad[0-9]+'. */
> > hcname +=3D 3;
> > while (hcname[0]>=3D '0'&& hcname[0]<=3D '9')
> > hcname++;
> > /* Skip 'ada[0-9]+'.
> > ppname +=3D 4;
> > while (ppname[0]>=3D '0'&& ppname[0]<=3D '9')
> > ppname++;
> >
> > return (strcmp(ppname, hcname) =3D=3D 0);
> >}
> >
> >That could work.
>=20
> Yes, I was thinking about something like that. May be just
> symmetric, so it could handle some cases of downgrade.
Ok, so this will handle hardcoded provider names. I think this is good
enough.
Now, what about fstab? There is a problem to figure out which disk we
booted from once we enter the kernel. I was wondering if we could detect
that someone is trying to mount root which from 'ad[0-9]+<X>' and
then we could scan all ada[0-9]+<X> looking for UFS file system and
/etc/fstab in there and / entry which matches vfs.root.mountfrom variable.
This should cover 99% of cases. 1% is for cases where another disk have
identical partitioning scheme and /etc/fstab file. There also might be
cases where someone defines vfs.root.mountfrom in /boot/loader.conf and
doesn't really use /etc/fstab.
> >Another possibility I was thinking of was to create GEOM providers for
> >both names and orphan the other name once one of them is opened for
> >writing.
>=20
> I've even implemented patch (posted on current@) with close idea (I
> was creating extra geom with legacy name), and it will have the same
> problem: if somebody open any partition on the device with the new
> name, all legacy names will become inaccessible (busy), and vice
> versa. It could be not a big problem if it would only be user's
> choice -- we could say just: "use one or another, not both". But
> provider could be chosen blindly by some GEOM class, such as glabel,
> and then it turns into pure lottery.
Good point.
--=20
Pawel Jakub Dawidek http://www.wheelsystems.com
FreeBSD committer http://www.FreeBSD.org
Am I Evil? Yes, I Am! http://yomoli.com
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