From owner-freebsd-hackers@FreeBSD.ORG  Sat Jun 19 15:48:27 2010
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Date: Sat, 19 Jun 2010 18:48:22 +0300
From: Jaakko Heinonen <jh@FreeBSD.org>
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Cc: phk@FreeBSD.org
Subject: [patch] extending alloc_unr(9) to allocate specific unit numbers
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Hi,

I wrote a patch to extend the kernel unit number allocator for
allocating specific unit numbers. The patch adds a new function
alloc_unr_specific() which returns the requested unit number if it is
free and -1 if the number is already allocated or out of the range.
Unlike alloc_unr(), alloc_unr_specific() may allocate memory and thus
sleep.

The patch is here:

	http://people.freebsd.org/~jh/patches/alloc_unr_specific.diff

I think that this functionality has been requested by some people.
Reviews/comments?

As an example here is md(4) converted to use
alloc_unr() / alloc_unr_specific():

	http://people.freebsd.org/~jh/patches/md-alloc_unr.diff

-- 
Jaakko