[Bug 1565817] Comment bridged from LTC Bugzilla

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------- Comment From mauricfo at br.ibm.com 2016-04-05 09:19 EDT-------
Hi @cyphermox,

> I sponsored multipath-tools as provided by Mauricio; some comments:

Thanks!

> [...] It all in all feels like the least
> intrusive way to deal with multipath disks on any random system (but I'm
> happy to be shown I'm mistaken! :)

Agree.

> [...] there *should* be some extensive
> testing of various multipath scenarios again before release to iron out any
> other last-minute bugs. [...]

Certainly.
As mentioned in LP 1551952, for some reassurance (w/ bugs it seems to be never enough :-), there's at least one test team running multipath testing around here,
which helped to find these 2 initial regressions from the merge, and hopefully any other bugs that the additional changes might introduce.

> [...] Among other things, we'd
> really benefit from testing with Tore Anderson's use case, which is
> different enough from the typical tests being done on FC and ppc64 to expose
> some fun bugs.

That looks interesting to follow up on.
Is the best way to contact him directly, or there are some things documented anywhere for me to check it out in advance?

Thanks!

> Finally, all these changes indeed need to go to Debian; we'd really benefit
> from reducing our delta even more, such as making sure all the patches are
> shared, including find_multipaths if possible.

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https://bugs.launchpad.net/bugs/1565817

Title:
  multipath: LVM physical volumes on individual paths

Status in multipath-tools package in Ubuntu:
  New

Bug description:
  == Comment: #0 - Mauricio Faria De Oliveira - 2016-04-04 10:02:55 ==
  ---Problem Description---
  multipath: LVM physical volumes on individual paths
   
  Contact Information = Mauricio Faria de Oliveira <mauricfo at linux.vnet.ibm.com> / Gabriel Krisman <krisman at linux.vnet.ibm.com> 
   
  This bug reports/patches 2 regressions introduced with multipath-tools 0.5.0+git1.656f8865-5ubuntu1 (see LP 1551952).

  1) The udev rule which removes partition nodes from individual paths
  is not working.

  This happens due to the introduction of the 'udev property blacklisting' feature (which blacklists devices if they don't have certain udev properties defined).
  Because 'multipath -c'  is run at udev rules PROGRAM-rule time, it can't read the required udev properties (defined by sg3-utils udev rules), because they are not yet written to the udev database -- this only happens after the rules finish processing (they would be available at RUN-rule time).
  The solution is to use 'multipath -u', which reads them directly from the udev program environment (and not from the not-yet-updated database) afaik, and makes things work at PROGRAM-rule time.

  This required a change between the local-top/init-top initramfs scripts.
  Since 'multipath -u' checks if multipathd is started, it moved into init-top, so it's started before udev rules are processed.
  While in there, the local-top script is now redundant with other initramfs scripts, and can be removed. See the changelog for details/explanation.

  2) The find_multipath options is no longer enabled by default.

  It's non-default upstream, and with the merge (when the downstream patch was removed), the change/setting was lost. 
  A new patch is introduced which explicitly enables it by the default.

  I'll add more details for the regression #1 shortly.

  Patch attached.

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