[rfc 11/18] slub: Acquire_slab() avoid loop

[Christoph Lameter <cl@linux.com>]

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Avoid the loop in acquire slab and simply fail if there is a conflict.

This will cause the next page on the lisdt to be considered.

Signed-off-by: Christoph Lameter <cl@linux.com>

---
 mm/slub.c |   23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2011-11-09 16:05:42.632059449 -0600
+++ linux-2.6/mm/slub.c	2011-11-09 16:06:06.802192215 -0600
@@ -1503,22 +1503,25 @@ static inline void *acquire_slab(struct
 	 * The old freelist is the list of objects for the
 	 * per cpu allocation list.
 	 */
-	do {
-		freelist = page->freelist;
-		counters = page->counters;
-		new.counters = counters;
-		if (mode)
-			new.inuse = page->objects;
+	freelist = page->freelist;
+	counters = page->counters;
+	new.counters = counters;
+	new.inuse = page->objects;
+	if (mode)
+		new.inuse = page->objects;
 
-		VM_BUG_ON(new.frozen);
-		new.frozen = 1;
+	VM_BUG_ON(new.frozen);
+	new.frozen = 1;
 
-	} while (!__cmpxchg_double_slab(s, page,
+	if (!__cmpxchg_double_slab(s, page,
 			freelist, counters,
 			NULL, new.counters,
-			"lock and freeze"));
+			"acquire_slab"))
+
+		return NULL;
 
 	remove_partial(n, page);
+	WARN_ON(!freelist);
 	return freelist;
 }
 

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