[dm-devel] [PATCH 0/3] md raid: enhancements to support the device mapper dm-raid target

[Mike Snitzer]

On Fri, Feb 13 2015 at  1:48pm -0500,
heinzm at redhat.com <heinzm at redhat.com> wrote:

> From: Heinz Mauelshagen <heinzm at redhat.com>
> 
> I'm enhancing the device mapper raid target (dm-raid) to take
> advantage of so far unused md raid kernel funtionality:
> takeover, reshape, resize, addition and removal of devices to/from raid sets.
> 
> This series of patches remove constraints doing so.
> 
> 
> Patch #1:
> add 2 API functions to allow dm-raid to access the raid takeover
> and resize functionality (namely md_takeover() and md_resize());
> reshape APIs are not needed in lieu of the existing personalilty ones
> 
> Patch #2:
> because device mapper core manages a request queue per mapped device
> utilizing the md make_request API to pass on bios via the dm-raid target,
> no md instance underneath it needs to manage a request queue of its own.
> Thus dm-raid can't use the md raid0 personality as is, because the latter
> accesses the request queue unconditionally in 3 places via mddev->queue
> which this patch addresses.
> 
> Patch #3:
> when dm-raid processes a down takeover to raid0, it needs to destroy
> any existing bitmap, because raid0 does not require one. The patch
> exports the bitmap_destroy() API to allow dm-raid to remove bitmaps.

Shouldn't you have cc'd the linux-raid mailing list and Neil Brown?