On 10/11/2016 11:17 AM, tang.junhui@zte.com.cn wrote:

> Hello Hannes, Ben,

> Could you have a review for this patch, any comment will be highly

> appreciated.

>

> Thanks,

> Tang

>

>

>

>

> 发件人:         Christophe Varoqui <christophe.varoqui@opensvc.com>

> 收件人:         tang.junhui@zte.com.cn,

> 抄送:        Bart Van Assche <bart.vanassche@sandisk.com>,
device-mapper

> development <dm-devel@redhat.com>, zhang.kai16@zte.com.cn

> 日期:         2016/10/11 14:59

> 主题:        Re: [dm-devel] [PATCH] libmultipath:
fix multipath -q

> command logic

> 发件人:        dm-devel-bounces@redhat.com

> ------------------------------------------------------------------------

>

>

>

> Hannes, Ben,

>

> are you ok with the solution to these two issues.

> Seems sane to me.

>

This actually is only part of the story.

The whole idea of issuing 'multipath' is to check if a given path 

_should_ be multipathed (as this is typically called from an udev event).

But as it's called from an udev event we cannot rely on the multipath 

daemon to be started; we might just handle an event which came in before

multipathd got started from systemd.

So checking for the PID file is not enough, we need to check if the 

daemon will be started eventually.

And in fact checking the PID file or calling mpath_connect() is 

equivalent, with the added advantage the mpath_connect() will start the

daemon _if enabled by systemd_.

So this patch doesn't help much, as it doesn't solve the main problem of

figuring out if multipathd _should_ be started.

I've done a patch for checking the '.wants' directories from systemd, 

but this obviously will only work if the OS is systemd-based.

And it's not really perfect, as there are corner-cases where just 

checking for the .wants directory is not enough.

Cheers,

Hannes

-- 

Dr. Hannes Reinecke              

         zSeries & Storage

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