Re: Collision of SLUB unique ID

[Christoph Lameter <clameter@sgi.com>]

On Tue, 10 Jun 2008, Yoichi Yuasa wrote:

> No, the kernel that applies it cannot boot. 

Hmmm... Ok here is an experimental patch that just disables merging for 
192 (in general a bad idea). If this works then we know at least where
to look for the solution.

---
 mm/slub.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2008-06-10 10:02:03.000000000 -0700
+++ linux-2.6/mm/slub.c	2008-06-10 10:04:04.000000000 -0700
@@ -171,7 +171,7 @@ static inline void ClearSlabDebug(struct
  * Set of flags that will prevent slab merging
  */
 #define SLUB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
-		SLAB_TRACE | SLAB_DESTROY_BY_RCU)
+		SLAB_TRACE | SLAB_DESTROY_BY_RCU | __SLAB_NOMERGE)
 
 #define SLUB_MERGE_SAME (SLAB_DEBUG_FREE | SLAB_RECLAIM_ACCOUNT | \
 		SLAB_CACHE_DMA)
@@ -187,6 +187,7 @@ static inline void ClearSlabDebug(struct
 /* Internal SLUB flags */
 #define __OBJECT_POISON		0x80000000 /* Poison object */
 #define __SYSFS_ADD_DEFERRED	0x40000000 /* Not yet visible via sysfs */
+#define __SLAB_NOMERGE		0x20000000 /* Never merge this slab */
 
 static int kmem_size = sizeof(struct kmem_cache);
 
@@ -2998,7 +2999,7 @@ void __init kmem_cache_init(void)
 	}
 	if (KMALLOC_MIN_SIZE <= 128) {
 		create_kmalloc_cache(&kmalloc_caches[2],
-				"kmalloc-192", 192, GFP_KERNEL);
+				"kmalloc-192", 192, GFP_KERNEL | __SLAB_NOMERGE);
 		caches++;
 	}
 

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