From: Jan Fajerski <jfajerski@suse.com>
Date: Fri, 15 May 2020 09:26:31 +0000 (+0200)
Subject: ceph-volume: support for mpath devices
X-Git-Tag: v15.2.9~122^2~114^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=refs%2Fpull%2F36928%2Fhead;p=ceph.git

ceph-volume: support for mpath devices

Signed-off-by: Jan Fajerski <jfajerski@suse.com>

Fixes: https://tracker.ceph.com/issues/45094
(cherry picked from commit ee8887f4c0ff4f91117f31b621b95c8d08019130)
---

diff --git a/doc/ceph-volume/lvm/prepare.rst b/doc/ceph-volume/lvm/prepare.rst
index 3683f6f5b66..fd40b7e1e1a 100644
--- a/doc/ceph-volume/lvm/prepare.rst
+++ b/doc/ceph-volume/lvm/prepare.rst
@@ -253,28 +253,20 @@ work for both bluestore and filestore OSDs::
 
 ``multipath`` support
 ---------------------
-Devices that come from ``multipath`` are not supported as-is. The tool will
-refuse to consume a raw multipath device and will report a message like::
+``multipath`` devices are support if ``lvm`` is configured properly.
 
-    -->  RuntimeError: Cannot use device (/dev/mapper/<name>). A vg/lv path or an existing device is needed
+**Leave it to LVM**
 
-The reason for not supporting multipath is that depending on the type of the
-multipath setup, if using an active/passive array as the underlying physical
-devices, filters are required in ``lvm.conf`` to exclude the disks that are part of
-those underlying devices.
+Most Linux distributions should ship their LVM2 package with
+``multipath_component_detection = 1`` in the default configuration. With this
+setting ``LVM`` ignores any device that is a multipath component and
+``ceph-volume`` will accordingly not touch these devices.
 
-It is unfeasible for ceph-volume to understand what type of configuration is
-needed for LVM to be able to work in various different multipath scenarios. The
-functionality to create the LV for you is merely a (naive) convenience,
-anything that involves different settings or configuration must be provided by
-a config management system which can then provide VGs and LVs for ceph-volume
-to consume.
-
-This situation will only arise when trying to use the ceph-volume functionality
-that creates a volume group and logical volume from a device. If a multipath
-device is already a logical volume it *should* work, given that the LVM
-configuration is done correctly to avoid issues.
+**Using filters**
 
+Should this setting be unavailable, a correct ``filter`` expression must be
+provided in ``lvm.conf``. ``ceph-volume`` must not be able to use both the
+multipath device and its multipath components.
 
 Storing metadata
 ----------------
diff --git a/src/ceph-volume/ceph_volume/util/disk.py b/src/ceph-volume/ceph_volume/util/disk.py
index 3e246ab357d..329915b3294 100644
--- a/src/ceph-volume/ceph_volume/util/disk.py
+++ b/src/ceph-volume/ceph_volume/util/disk.py
@@ -330,7 +330,7 @@ def is_device(dev):
     # use lsblk first, fall back to using stat
     TYPE = lsblk(dev).get('TYPE')
     if TYPE:
-        return TYPE == 'disk'
+        return TYPE in ['disk', 'mpath']
 
     # fallback to stat
     return _stat_is_device(os.lstat(dev).st_mode)
@@ -747,7 +747,7 @@ def get_devices(_sys_block_path='/sys/block'):
     for block in block_devs:
         devname = os.path.basename(block[0])
         diskname = block[1]
-        if block[2] != 'disk':
+        if block[2] not in ['disk', 'mpath']:
             continue
         sysdir = os.path.join(_sys_block_path, devname)
         metadata = {}