slub: automatically reserve bytes at the end of slab

There is no "struct" for slub's slab, it shares with struct page.
But struct page is very small, it is insufficient when we need
to add some metadata for slab.

So we add a field "reserved" to struct kmem_cache, when a slab
is allocated, kmem_cache->reserved bytes are automatically reserved
at the end of the slab for slab's metadata.

Changed from v1:
	Export the reserved field via sysfs

Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 8b6e8ae5d5ca..ae0093cc5189 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -83,6 +83,7 @@ struct kmem_cache {
         void (*ctor)(void *);
         int inuse;              /* Offset to metadata */
         int align;              /* Alignment */
+        int reserved;           /* Reserved bytes at the end of slabs */
         unsigned long min_partial;
         const char *name;       /* Name (only for display!) */
         struct list_head list;  /* List of slab caches */