linux-kernel - [PATCH] fix BUG_ON(!PageSlab) from fallback

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Date:	Thu, 4 Jan 2007 17:49:00 +0000 (GMT)
From:	Hugh Dickins <hugh@...itas.com>
To:	Andrew Morton <akpm@...l.org>
cc:	Christoph Lameter <clameter@....com>,
	Pekka J Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] fix BUG_ON(!PageSlab) from fallback_alloc

pdflush hit the BUG_ON(!PageSlab(page)) in kmem_freepages called from
fallback_alloc: cache_grow already freed those pages when alloc_slabmgmt
failed.  But it wouldn't have freed them if __GFP_NO_GROW, so make sure
fallback_alloc doesn't waste its time on that case.

Signed-off-by: Hugh Dickins <hugh@...itas.com>
___
Fixes a CONFIG_NUMA regression introduced in 2.6.20-rc1.  Or you may
feel it's cleaner for cache_grow to skip its kmem_freepages when objp
is input: patch below is slightly simpler, but I've no strong feeling.

 mm/slab.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- 2.6.20-rc3/mm/slab.c	2007-01-01 10:30:46.000000000 +0000
+++ linux/mm/slab.c	2007-01-04 17:30:11.000000000 +0000
@@ -3281,7 +3281,7 @@ retry:
 					flags | GFP_THISNODE, nid);
 	}

-	if (!obj) {
+	if (!obj && !(flags & __GFP_NO_GROW)) {
 		/*
 		 * This allocation will be performed within the constraints
 		 * of the current cpuset / memory policy requirements.
@@ -3310,7 +3310,7 @@ retry:
 					 */
 					goto retry;
 			} else {
-				kmem_freepages(cache, obj);
+				/* cache_grow already freed obj */
 				obj = NULL;
 			}
 		}
-
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