On 02/10/2011 11:00 PM, Mike Snitzer wrote: > On Tue, Feb 01 2011 at 10:38am -0500, > Hannes Reinecke <hare@xxxxxxx> wrote: > >> 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. > > I found the following commit but it doesn't have any meaningful changes: > 1e53326 Allow zero paths for device-mapper strings > > Could you be more explicit on which commits you're thinking of? Ah, I just rechecked the code. There used to be quite a few missing NULL pointer checks, especially if mpp->pg or mpp->paths are NULL. But they seem to have been fixed now. So ignore my objection here. 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
