linux-kernel - [PATCH] regression: vmalloc easily fail.

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Message-Id: <1225234513-3996-1-git-send-email-glommer@redhat.com>
Date:	Tue, 28 Oct 2008 20:55:13 -0200
From:	Glauber Costa <glommer@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, avi@...hat.com, aliguori@...emonkey.ws,
	npiggin@...e.de, Jeremy Fitzhardinge <jeremy@...p.org>,
	Krzysztof Helt <krzysztof.h1@...zta.fm>
Subject: [PATCH] regression: vmalloc easily fail.

Commit db64fe02258f1507e13fe5212a989922323685ce broke
KVM (the symptom) for me. The cause is that vmalloc
allocations fail, despite of the fact that /proc/meminfo
shows plenty of vmalloc space available.

After some investigation, it seems to me that the current
way to compute the next addr in the rb-tree transversal
leaves a spare page between each allocation. After a few
allocations, regardless of their size, we run out of vmalloc
space.

Signed-off-by: Glauber Costa <glommer@...hat.com>
Cc: Jeremy Fitzhardinge <jeremy@...p.org>
Cc: Krzysztof Helt <krzysztof.h1@...zta.fm>
---
 mm/vmalloc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 0365369..a33b0d1 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -363,7 +363,7 @@ retry:
 		}
 
 		while (addr + size >= first->va_start && addr + size <= vend) {
-			addr = ALIGN(first->va_end + PAGE_SIZE, align);
+			addr = ALIGN(first->va_end, align);
 
 			n = rb_next(&first->rb_node);
 			if (n)
-- 
1.5.6.5

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