On 01/31/2011 07:34 PM, Mike Snitzer wrote: > On Mon, Jan 31 2011 at 1:09pm -0500, > Moger, Babu <Babu.Moger@xxxxxxx> wrote: > >> Looks good to me. >> >>> -----Original Message----- >>> From: Mike Snitzer [mailto:snitzer@xxxxxxxxxx] >>> Sent: Monday, January 31, 2011 10:14 AM >>> To: dm-devel@xxxxxxxxxx >>> Cc: Mike Snitzer; Moger, Babu >>> Subject: [PATCH 2/2] dm mpath: allow table load with 0 priority groups >>> >>> If an mpath device is held open when all paths in the last priority >>> group have failed userspace multipathd will attempt to reload the >>> associated DM table to reflect that the device no longer has any >>> priority groups. But the reload attempt always failed because the >>> multipath target did not allow 0 priority groups. >>> >>> Adjust multipath target to allow a table with both 0 priority groups >>> and 0 for the initial priority group number. >>> >>> All multipath target messages related to priority group (enable_group, >>> disable_group, switch_group) will properly handle a priority group of >>> 0 (will cause error). >>> >>> When reloading a multipath table with 0 priority groups, userspace >>> multipathd must be updated to specify an initial priority group number >>> of 0 (rather than 1). >> >> Looks like we still have some action from multipath tool. CCing Ben.. > > Right, I looked in to the multipath-tools change. Here is an RFC patch. > > Inlined "FIXME"s pose the relevant questions. I held off on having > select_path_group() return 0 when !mpp->pg because I wasn't confident > that I wouldn't break multipathd in some unintuitive way. > > I did audit the various callers (indirect through setup_map call): > > update_path_groups > ev_add_path > ev_remove_path > > (all above first call setup_map) > > setup_map() > - mpp->bestpg = select_path_group() > - assemble_map() -- establishes mp->params > > do_map() > > Even though I verified that much I wasn't completely confident in > changing select_path_group()'s defualt return of 1 -- so I localized the > change to where I _knew_ it was safe (assemble_map): > > diff --git a/libmultipath/dmparser.c b/libmultipath/dmparser.c > index 1ef3aad..97b6420 100644 > --- a/libmultipath/dmparser.c > +++ b/libmultipath/dmparser.c > @@ -52,6 +52,7 @@ assemble_map (struct multipath * mp) > int i, j; > int shift, freechar; > int minio; > + int nr_priority_groups, initial_pg_nr; > char * p; > struct pathgroup * pgp; > struct path * pp; > @@ -60,9 +61,19 @@ assemble_map (struct multipath * mp) > p = mp->params; > freechar = sizeof(mp->params); > > + nr_priority_groups = VECTOR_SIZE(mp->pg); > + /* > + * FIXME: make this conditional on multipath target version? > + * - but no existing code is conditional on multipath target version, > + * nor does dm_drvprereq() store the version for code to do so. > + * - thing is older multipath never allowed nr_priority_groups=0 so > + * it doesn't _really_ matter if initial_pg_nr=0 here... > + */ > + initial_pg_nr = (nr_priority_groups ? mp->bestpg : 0); > + > shift = snprintf(p, freechar, "%s %s %i %i", > mp->features, mp->hwhandler, > - VECTOR_SIZE(mp->pg), mp->bestpg); > + nr_priority_groups, initial_pg_nr); > > if (shift >= freechar) { > fprintf(stderr, "mp->params too small\n"); > diff --git a/libmultipath/switchgroup.c b/libmultipath/switchgroup.c > index 025a95d..82c30ad 100644 > --- a/libmultipath/switchgroup.c > +++ b/libmultipath/switchgroup.c > @@ -41,7 +41,7 @@ select_path_group (struct multipath * mpp) > struct pathgroup * pgp; > > if (!mpp->pg) > - return 1; > + return 1; /* FIXME: return 0 here? */ > > vector_foreach_slot (mpp->pg, pgp, i) { > if (!pgp->paths) > I have a similar patchset in my multipath-tools tree, to allow maps with zero paths, too. However, there are quite a few places which required checking, as we're basically _never_ check if a pointer is NULL before accessing it. With a bit of luck I'll find some time to send out the patchset. Otherwise you could have a look at git://git.kernel.org/pub/scm/linux/kernel/git/hare/multipath-tools.git branch sles11-sp1 will have the most recent stuff. Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@xxxxxxx +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: Markus Rex, HRB 16746 (AG Nürnberg) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
