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Date:   Wed, 15 May 2019 04:38:06 -0400 (EDT)
From:   Pankaj Gupta <pagupta@redhat.com>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     snitzer@redhat.com, stable@vger.kernel.org,
        Jan Kara <jack@suse.cz>, Ira Weiny <ira.weiny@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Keith Busch <keith.busch@intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org,
        dm-devel@redhat.com, linux-kernel@vger.kernel.org
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Subject: Re: [PATCH] dax: Arrange for dax_supported check to span multiple
 devices
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Thread-Topic: Arrange for dax_supported check to span multiple devices
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> 
> Pankaj reports that starting with commit ad428cdb525a "dax: Check the
> end of the block-device capacity with dax_direct_access()" device-mapper
> no longer allows dax operation. This results from the stricter checks in
> __bdev_dax_supported() that validate that the start and end of a
> block-device map to the same 'pagemap' instance.
> 
> Teach the dax-core and device-mapper to validate the 'pagemap' on a
> per-target basis. This is accomplished by refactoring the
> bdev_dax_supported() internals into generic_fsdax_supported() which
> takes a sector range to validate. Consequently generic_fsdax_supported()
> is suitable to be used in a device-mapper ->iterate_devices() callback.
> A new ->dax_supported() operation is added to allow composite devices to
> split and route upper-level bdev_dax_supported() requests.
> 
> Fixes: ad428cdb525a ("dax: Check the end of the block-device...")
> Cc: <stable@vger.kernel.org>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Mike Snitzer <snitzer@redhat.com>
> Cc: Keith Busch <keith.busch@intel.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Reported-by: Pankaj Gupta <pagupta@redhat.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Thank you for the patch. Looks good to me. 
I also tested the patch and it works well.

Reviewed-and-Tested-by: Pankaj Gupta <pagupta@redhat.com> 

Best regards,
Pankaj