[dm-devel] [PATCH v5 22/22] multipath.rules: find_multipaths "smart" logic

[Hannes Reinecke]

On Sat, 14 Apr 2018 00:00:15 +0200
Martin Wilck <mwilck at suse.com> wrote:

> When the first path to a device appears, we don't know if more paths
> are going to follow. find_multipath "smart" logic attempts to solve
> this dilemma by waiting for additional paths for a configurable time
> before giving up and releasing single paths to upper layers.
> 
> These rules apply only if both find_multipaths is set to "smart" in
> multipath.conf. In this mode, multipath -u sets
> DM_MULTIPATH_DEVICE_PATH=2 if there's no clear evidence wheteher a
> given device should be a multipath member (not blacklisted, not
> listed as "failed", not in WWIDs file, not member of an existing map,
> only one path seen yet). In this case, "multipath -u" also sets the
> variable FIND_MULTIPATHS_WAIT_UNIL to a relative time stamp (we need
> to use relative "monotonic" time stamps because this may be triggered
> early during boot, before system "calendar" time is correctly
> initialized).
> 
> In the DM_MULTIPATH_DEVICE_PATH=2 case, pretend that the path is
> multipath member, disallow further processing by systemd (allowing
> multipathd some time to grab the path), and set a systemd timer to
> check again after the given timeout. If the path is still not
> multipathed by then, pass it on to systemd for further processing.
> 
> Signed-off-by: Martin Wilck <mwilck at suse.com>
> Reviewed-by: Benjamin Marzinski <bmarzins at redhat.com>
> ---
>  multipath/multipath.rules | 61
> ++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 58
> insertions(+), 3 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare at suse.com>

Cheers,

Hannes