mm: slub: work around unneeded lockdep warning

The slub code does some setup during early boot in
early_kmem_cache_node_alloc() with some local data.  There is no
possible way that another CPU can see this data, so the slub code
doesn't unnecessarily lock it.  However, some new lockdep asserts
check to make sure that add_partial() _always_ has the list_lock
held.

Just add the locking, even though it is technically unnecessary.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: W4TCH0UT <ateekujjawal@gmail.com>
Signed-off-by: Anik1199 <anik9280@gmail.com>

Conflicts:
	mm/slub.c

1 files changed, 6 insertions, 3 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 82a3fffe6..06fb1a9d5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1,3 +1,4 @@
+
 /*
  * SLUB: A slab allocator that limits cache line use instead of queuing
  * objects in per cpu and per node lists.
@@ -3077,10 +3078,12 @@ static void early_kmem_cache_node_alloc(int node)
 	inc_slabs_node(kmem_cache_node, node, page->objects);
 
 	/*
-	 * No locks need to be taken here as it has just been
-	 * initialized and there is no concurrent access.
+	 * the lock is for lockdep's sake, not for any actual
+	 * race protection
 	 */
-	__add_partial(n, page, DEACTIVATE_TO_HEAD);
+	spin_lock(&n->list_lock);
+	add_partial(n, page, DEACTIVATE_TO_HEAD);
+	spin_unlock(&n->list_lock);
 }
 
 static void free_kmem_cache_nodes(struct kmem_cache *s)