[dm-devel] [PATCH v3 0/7] Fix muitpath/multipathd flush issue

[Benjamin Marzinski]

If a multipath device is removed, and check_path() checks one of its
paths before multipathd processes either the uevent or the dm event from
removing it, multipathd will recreate the removed device. This happens
because check_path() will continute to check the removed device's former
paths until an event arrives removing the device.  A missing multpath
device will cause the update_multipath_strings() call to fail, setting
pp->dmstate to PSTATE_UNDEF.  If the path is up, this dmstate will cause
reinstate_path() to be called, which will also fail, because the
multipath device doesn't exist.  This will trigger a reload, restoring
the recently removed device.

This patchset handles this is two ways. The first two patches directly
fix these issues in check_path(), so that a missing multipath device
will no longer get recreated when checking one of its former paths.

The other 5 patches add a "multipathd del maps" command, and make the
mutipath command delegate flush operations to multipathd so multipathd's
state remains in sync with the kernel's, while doing removes.

Changes from v1:
0001:	This is completely different. I've change how patch 0002 detects
	when a multipath device has disappeared. Instead of do_get_info,
	I need more return values on dm_get_map/status, and the
	update_multipath_* functions. I have used symbolic return
	values, which was the objection to the previous patch. I tried
	to picked generic enough names that they could be used for other
	devmapper.c functions as well.

0002:	At Martin's suggestion, multipath now differentiates between dm
	failures and a missing multipath device in
	update_multipath_strings(). So there is no need to recheck if
	the device is missing.

0006:	Added some man page info that was previously in patch 0007

0007:	Removed mentions of the -D option in the man page and usage
	output.

Changes from v2 (all are Martin's suggestions):
0001:	Using dm_task_get_errno() and changed the names and values of
	the symbolic returns.

0002:	Changed symbolic return names, and improved some logging.

Benjamin Marzinski (7):
  libmultipath: make dm_get_map/status return codes symbolic
  multipathd: fix check_path errors with removed map
  libmultipath: make dm_flush_maps only return 0 on success
  multipathd: add "del maps" multipathd command
  multipath: make flushing maps work like other commands
  multipath: delegate flushing maps to multipathd
  multipath: add option to skip multipathd delegation

 libmultipath/config.h      |  4 ++-
 libmultipath/configure.h   |  3 --
 libmultipath/devmapper.c   | 63 +++++++++++++++++++++++++-------------
 libmultipath/devmapper.h   |  8 ++++-
 libmultipath/structs_vec.c | 45 +++++++++++++++------------
 multipath/main.c           | 44 ++++++++++++++++++--------
 multipath/multipath.8      |  4 +--
 multipathd/cli.c           |  1 +
 multipathd/cli_handlers.c  | 19 ++++++++++++
 multipathd/cli_handlers.h  |  1 +
 multipathd/main.c          | 57 ++++++++++++++++------------------
 multipathd/main.h          |  1 +
 12 files changed, 160 insertions(+), 90 deletions(-)

-- 
2.17.2