slab: infrastructure for bulk object allocation and freeing

Add the basic infrastructure for alloc/free operations on pointer arrays.
It includes a generic function in the common slab code that is used in
this infrastructure patch to create the unoptimized functionality for slab
bulk operations.

Allocators can then provide optimized allocation functions for situations
in which large numbers of objects are needed.  These optimization may
avoid taking locks repeatedly and bypass metadata creation if all objects
in slab pages can be used to provide the objects required.

Allocators can extend the skeletons provided and add their own code to the
bulk alloc and free functions.  They can keep the generic allocation and
freeing and just fall back to those if optimizations would not work (like
for example when debugging is on).

Signed-off-by: Christoph Lameter <[email protected]>
Signed-off-by: Jesper Dangaard Brouer <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/slab.h

@@ -163,6 +163,15 @@ void slabinfo_show_stats(struct seq_file *m, struct kmem_cache *s);
 ssize_t slabinfo_write(struct file *file, const char __user *buffer,
 		       size_t count, loff_t *ppos);
 
+/*
+ * Generic implementation of bulk operations
+ * These are useful for situations in which the allocator cannot
+ * perform optimizations. In that case segments of the objecct listed
+ * may be allocated or freed using these operations.
+ */
+void __kmem_cache_free_bulk(struct kmem_cache *, size_t, void **);
+bool __kmem_cache_alloc_bulk(struct kmem_cache *, gfp_t, size_t, void **);
+
 #ifdef CONFIG_MEMCG_KMEM
 /*
  * Iterate over all memcg caches of the given root cache. The caller must hold