Re: [dm-devel] Opening a dm device reads from cache, not the device.

[Heinz Mauelshagen <mauelshagen redhat com>]

Is this dm-raid45 ?

If so, you'll need to add cluster logic to it (ie. taking locks
out on stripe cache accesses, invalidating stripes etc).

On Wed, Feb 15, 2006 at 05:05:28PM -0700, Allen Jack wrote:
> I have a RAID5 plugin that is also used with clustering.  I open the
> raid device (created in device-mapper) using the O_SYNC and O_DIRECT
> flags, but it seems to read the data from a cache somewhere.  I put a
> printk in my plugin map function, but it doesn't get hit.  If another
> node in the cluster changes the data on the disk, it never gets
> refreshed on this node because of the caching.
> 
> Is there any way to turn off the caching so that all read requests come
> to my plugin?  And where is the caching taking place?
> 
> Thanks,
> 
> Allen
> 
> Allen Jack
> email - ajack novell com
> Novell, Inc., the leading provider of information solutions
> http://www.novell.com
> 
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Heinz Mauelshagen                                 Red Hat GmbH
Consulting Development Engineer                   Am Sonnenhang 11
Cluster and Storage Development                   56242 Marienrachdorf
                                                  Germany
Mauelshagen RedHat com                            +49 2626 141200
                                                       FAX 924446
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