linux-kernel - Re: bug in lmb_enforce_memory

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Message-Id: <20080815.152501.193746275.davem@davemloft.net>
Date:	Fri, 15 Aug 2008 15:25:01 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	michael@...erman.id.au
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Subject: Re: bug in lmb_enforce_memory_limit()

From: Michael Ellerman <michael@...erman.id.au>
Date: Thu, 14 Aug 2008 21:26:53 +1000

> Perhaps after the first loop we should set memory_limit to equal
> lmb_end_of_DRAM(), then the second loop should work as it is.

Sounds great.  Mind if I push the following to Linus?

lmb: Fix reserved region handling in lmb_enforce_memory_limit().

The idea of the implementation of this fix is from Michael Ellerman.

This function has two loops, but they each interpret the memory_limit
value differently.  The first loop interprets it as a "size limit"
whereas the second loop interprets it as an "address limit".

Before the second loop runs, reset memory_limit to lmb_end_of_DRAM()
so that it all works out.

Signed-off-by: David S. Miller <davem@...emloft.net>

diff --git a/lib/lmb.c b/lib/lmb.c
index 5d7b928..97e5470 100644
--- a/lib/lmb.c
+++ b/lib/lmb.c
@@ -462,6 +462,8 @@ void __init lmb_enforce_memory_limit(u64 memory_limit)
 	if (lmb.memory.region[0].size < lmb.rmo_size)
 		lmb.rmo_size = lmb.memory.region[0].size;

+	memory_limit = lmb_end_of_DRAM();
+
 	/* And truncate any reserves above the limit also. */
 	for (i = 0; i < lmb.reserved.cnt; i++) {
 		p = &lmb.reserved.region[i];
--
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