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Re: [dm-devel] Resizing multipath maps: reload ioctl failed: Invalid argument


Tore Anderson wrote:
>   Hi.  I'm trying to resize multipath maps, but there appears to be
>  something wrong with the ioctl call...  I resized the "www" volume on
>  the storage array from 25GB to 45GB, and attempted to reload it on the
>  host, which is running 2.6.23-rc3 and multipath-tools 0.4.7.  It
>  resulted in the following:

It's due to kernel device-mapper restriction.

multipath-tools uses no_flush suspend of device-mapper device
to save I/O errors in all-paths-down case.
(Without the option, device-mapper needs to flush all pending I/Os,
 that will result in I/O errors if there is no working path.)

For no_flush suspend, resizing is disabled because of known dead-lock:
it requires a lock that can be kept hold until the pending I/Os
are flushed.

>   Ultimately I found no other way to make this work but to umount the
>  file system, then run "multipath -f www; multipath", which kind of
>  defeated the point of fancy online resizing support in the file system
>  and storage array since I need downtime to do it.  Is there any other
>  way to make online resizing work?

A workaround for it would be using modified multipath-tools which doesn't
use no_noflush.

Jun'ichi Nomura, NEC Corporation of America

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