linux-kernel - Re: [PATCH] resource: make sure requested range intersects root range

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Date:	Wed, 11 Jul 2012 22:54:12 +0800
From:	Ram Pai <linuxram@...ibm.com>
To:	"Purdila, Octavian" <octavian.purdila@...el.com>
Cc:	Ram Pai <linuxram@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [PATCH] resource: make sure requested range intersects root range

On Wed, Jul 11, 2012 at 02:06:10PM +0300, Purdila, Octavian wrote:
> On Wed, Jul 11, 2012 at 5:09 AM, Ram Pai <linuxram@...ibm.com> wrote:
> 
> >
> > Wait.. I am not sure this will fix the problem entirely. The above check
> > will handle the case where the range requested is entirey out of the
> > root's range.  But if the requested range overlapps that of the root
> > range, we will still call __reserve_region_with_split() and end up with
> > a recursion if there is a overflow. Wont we?
> >
> 
> Good catch. I will fix this as well as address Andrew's and Joe's
> comments in a new patch. The only question is how to handle the
> overlap case:
> 
> (a) abort the whole request or
> 
> (b) try to reserve the part that overlaps (and adjust the request to
> avoid the overflow)
> 
> I think (b) is more in line with the current implementation for reservations.


I prefer (b).  following patch should handle that.

diff --git a/kernel/resource.c b/kernel/resource.c
index e1d2b8e..dd87fde 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -780,6 +780,10 @@ static void __init __reserve_region_with_split(struct resource *root,
 
 	if (conflict->start > start)
 		__reserve_region_with_split(root, start, conflict->start-1, name);
+
+	if (conflict->end == parent->end )
+		return;
+
 	if (conflict->end < end)
 		__reserve_region_with_split(root, conflict->end+1, end, name);
 }

RP

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