[RFC PATCH v4 5/9] slub: Introduce freeze_slab()

[chengming.zhou@linux.dev]

From: Chengming Zhou <zhouchengming@bytedance.com>

We will have unfrozen slabs out of the node partial list later, so we
need a freeze_slab() function to freeze the partial slab and get its
freelist.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slub.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/mm/slub.c b/mm/slub.c
index 1880b483350e..edf567971679 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3098,6 +3098,33 @@ static inline void *get_freelist(struct kmem_cache *s, struct slab *slab)
 	return freelist;
 }
 
+/*
+ * Freeze the partial slab and return the pointer to the freelist.
+ */
+static inline void *freeze_slab(struct kmem_cache *s, struct slab *slab)
+{
+	struct slab new;
+	unsigned long counters;
+	void *freelist;
+
+	do {
+		freelist = slab->freelist;
+		counters = slab->counters;
+
+		new.counters = counters;
+		VM_BUG_ON(new.frozen);
+
+		new.inuse = slab->objects;
+		new.frozen = 1;
+
+	} while (!slab_update_freelist(s, slab,
+		freelist, counters,
+		NULL, new.counters,
+		"freeze_slab"));
+
+	return freelist;
+}
+
 /*
  * Slow path. The lockless freelist is empty or we need to perform
  * debugging duties.
-- 
2.20.1