[PATCH storage 04/13] multipath: add storage plugin for multipath LUNs

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Expose the dm-multipath maps present on a node as a first-class storage
of raw volumes, each keyed by its WWID and reachable at the WWID-stable
path /dev/disk/by-id/dm-uuid-mpath-<wwid>. The maps are assembled by
multipathd from the cluster-wide allow-list, so the storage carries no
configuration of its own and only reflects what is already there.

This is meant primarily as the base of a shared LVM storage, giving a
volume group on a multipath LUN full path redundancy without any manual
device wiring.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---
 src/PVE/Storage.pm                 |   2 +
 src/PVE/Storage/Makefile           |   3 +-
 src/PVE/Storage/MultipathPlugin.pm | 186 +++++++++++++++++++++++++++++
 3 files changed, 190 insertions(+), 1 deletion(-)
 create mode 100644 src/PVE/Storage/MultipathPlugin.pm

diff --git a/src/PVE/Storage.pm b/src/PVE/Storage.pm
index 64ea9da..4daeecf 100755
--- a/src/PVE/Storage.pm
+++ b/src/PVE/Storage.pm
@@ -39,6 +39,7 @@ use PVE::Storage::ZFSPlugin;
 use PVE::Storage::PBSPlugin;
 use PVE::Storage::BTRFSPlugin;
 use PVE::Storage::ESXiPlugin;
+use PVE::Storage::MultipathPlugin;
 
 # Storage API version. Increment it on changes in storage API interface.
 use constant APIVER => 15;
@@ -64,6 +65,7 @@ PVE::Storage::ZFSPlugin->register();
 PVE::Storage::PBSPlugin->register();
 PVE::Storage::BTRFSPlugin->register();
 PVE::Storage::ESXiPlugin->register();
+PVE::Storage::MultipathPlugin->register();
 
 # load third-party plugins
 if (-d '/usr/share/perl5/PVE/Storage/Custom') {
diff --git a/src/PVE/Storage/Makefile b/src/PVE/Storage/Makefile
index a67dc25..d76ec25 100644
--- a/src/PVE/Storage/Makefile
+++ b/src/PVE/Storage/Makefile
@@ -14,7 +14,8 @@ SOURCES= \
 	PBSPlugin.pm \
 	BTRFSPlugin.pm \
 	LvmThinPlugin.pm \
-	ESXiPlugin.pm
+	ESXiPlugin.pm \
+	MultipathPlugin.pm
 
 .PHONY: install
 install:
diff --git a/src/PVE/Storage/MultipathPlugin.pm b/src/PVE/Storage/MultipathPlugin.pm
new file mode 100644
index 0000000..91fc489
--- /dev/null
+++ b/src/PVE/Storage/MultipathPlugin.pm
@@ -0,0 +1,186 @@
+package PVE::Storage::MultipathPlugin;
+
+use strict;
+use warnings;
+
+use PVE::Multipath;
+use PVE::Storage::Plugin;
+
+use base qw(PVE::Storage::Plugin);
+
+# A block-LUN provider over device-mapper multipath: it exposes the maps present on the node as raw
+# volumes keyed by their WWID, reachable at the WWID-stable /dev/disk/by-id/dm-uuid-mpath-<wwid>
+# path. The maps are assembled by multipathd from the cluster-wide allow-list, so this storage has
+# no configuration of its own and only reflects what is there. Its main use is as the 'base' of a
+# shared LVM storage.
+
+sub type {
+    return 'multipath';
+}
+
+sub plugindata {
+    return {
+        content => [{ images => 1, none => 1 }, { images => 1 }],
+        format => [{ raw => 1 }, 'raw'],
+        select_existing => 1,
+        'sensitive-properties' => {},
+    };
+}
+
+sub properties {
+    return {};
+}
+
+sub options {
+    return {
+        nodes => { optional => 1 },
+        shared => { optional => 1 },
+        disable => { optional => 1 },
+        content => { optional => 1 },
+        bwlimit => { optional => 1 },
+    };
+}
+
+# the volume name is the LUN's WWID
+sub parse_volname {
+    my ($class, $volname) = @_;
+
+    if ($volname =~ m!^([a-zA-Z0-9._:-]+)$!) {
+        return ('images', $1, undef, undef, undef, undef, 'raw');
+    }
+
+    die "unable to parse multipath volume name '$volname'\n";
+}
+
+sub filesystem_path {
+    my ($class, $scfg, $volname, $snapname) = @_;
+
+    die "snapshot is not possible on multipath storage\n" if defined($snapname);
+
+    my ($vtype, $wwid, $vmid) = $class->parse_volname($volname);
+
+    my $path = "/dev/disk/by-id/dm-uuid-mpath-$wwid";
+
+    return wantarray ? ($path, $vmid, $vtype) : $path;
+}
+
+sub create_base {
+    die "can't create base images in multipath storage\n";
+}
+
+sub clone_image {
+    die "can't clone images in multipath storage\n";
+}
+
+sub alloc_image {
+    die "can't allocate space in multipath storage\n";
+}
+
+sub free_image {
+    die "can't free space in multipath storage\n";
+}
+
+sub list_images {
+    my ($class, $storeid, $scfg, $vmid, $vollist, $cache) = @_;
+
+    my $res = [];
+
+    # multipath LUNs have no owning guest
+    return $res if defined($vmid) && !$vollist;
+
+    $cache->{multipath_maps} //= eval { PVE::Multipath::get_maps() } // [];
+
+    for my $map ($cache->{multipath_maps}->@*) {
+        next if !defined($map->{wwid});
+
+        my $volid = "$storeid:$map->{wwid}";
+        if ($vollist) {
+            next if !grep { $_ eq $volid } @$vollist;
+        }
+
+        push @$res,
+            {
+                volid => $volid,
+                format => 'raw',
+                size => $map->{size} // 0,
+                vmid => 0,
+            };
+    }
+
+    return $res;
+}
+
+sub list_volumes {
+    my ($class, $storeid, $scfg, $vmid, $content_types) = @_;
+
+    my $res = $class->list_images($storeid, $scfg, $vmid);
+    $_->{content} = 'images' for $res->@*;
+
+    return $res;
+}
+
+sub status {
+    my ($class, $storeid, $scfg, $cache) = @_;
+
+    my $active = PVE::Multipath::is_running() ? 1 : 0;
+
+    return (0, 0, 0, $active);
+}
+
+sub activate_storage {
+    my ($class, $storeid, $scfg, $cache) = @_;
+
+    PVE::Multipath::assert_supported();
+    # nothing to log into: multipathd assembles the maps from the allow-list
+}
+
+sub deactivate_storage {
+    my ($class, $storeid, $scfg, $cache) = @_;
+
+    # the maps are shared infrastructure, do not tear them down
+}
+
+sub check_connection {
+    my ($class, $storeid, $scfg) = @_;
+
+    return PVE::Multipath::is_running() ? 1 : 0;
+}
+
+sub activate_volume {
+    my ($class, $storeid, $scfg, $volname, $snapname, $cache) = @_;
+
+    my ($vtype, $wwid) = $class->parse_volname($volname);
+
+    my $map = PVE::Multipath::wait_for_map($wwid);
+    die "multipath map for WWID '$wwid' is not present - is it in the multipath"
+        . " allow-list and are its paths up?\n"
+        if !$map;
+}
+
+sub deactivate_volume {
+    my ($class, $storeid, $scfg, $volname, $snapname, $cache) = @_;
+
+    # do not drop the map, it is shared infrastructure
+}
+
+sub volume_resize {
+    my ($class, $scfg, $storeid, $volname, $size, $running) = @_;
+
+    die "volume resize is not possible on multipath storage\n";
+}
+
+sub volume_has_feature {
+    my ($class, $scfg, $feature, $storeid, $volname, $snapname, $running) = @_;
+
+    return { copy => { current => 1 } }->{$feature}->{current};
+}
+
+sub volume_export_formats {
+    return ();
+}
+
+sub volume_import_formats {
+    return ();
+}
+
+1;
-- 
2.47.3