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 there,
> >>>>and it is absolutely not trivial. If we take the "symlinking" way (patch
> >>>>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) == 0)
> > return (true);
> > if (strncmp(hcname, "ad", 2) != 0 ||
> > hcname[2]< '0' || hcname[2]> '9') {
> > return (false);
> > }
> > if (strncmp(ppname, "ada", 3) != 0 ||
> > ppname[3]< '0' || ppname[3]> '9') {
> > return (false);
> > }
> > /* Skip 'ad[0-9]+'. */
> > hcname += 3;
> > while (hcname[0]>= '0'&& hcname[0]<= '9')
> > hcname++;
> > /* Skip 'ada[0-9]+'.
> > ppname += 4;
> > while (ppname[0]>= '0'&& ppname[0]<= '9')
> > ppname++;
> >
> > return (strcmp(ppname, hcname) == 0);
> >}
> >
> >That could work.
>
> 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. > > 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. -- Pawel Jakub Dawidek http://www.wheelsystems.com FreeBSD committer http://www.FreeBSD.org Am I Evil? Yes, I Am! http://yomoli.com
pgpGT9bP9O3pb.pgp
Description: PGP signature
