mm/slab: move kmalloc_slab() to mm/slab.h

In preparation for the next patch, move the kmalloc_slab() function to
the header, as it will have callers from two files, and make it inline.
To avoid unnecessary bloat, remove all size checks/warnings from
kmalloc_slab() as they just duplicate those in callers, especially after
recent changes to kmalloc_size_roundup(). We just need to adjust handling
of zero size in __do_kmalloc_node(). Also we can stop handling NULL
result from kmalloc_slab() there as that now cannot happen (unless
called too early during boot).

The size_index array becomes visible so rename it to a more specific
kmalloc_size_index.

Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: David Rientjes <rientjes@google.com>
Tested-by: David Rientjes <rientjes@google.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

1 files changed, 26 insertions, 2 deletions

diff --git a/mm/slab.h b/mm/slab.h
index 35a55c4a407d..7d7cc7af614e 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -389,8 +389,32 @@ extern const struct kmalloc_info_struct {
 void setup_kmalloc_cache_index_table(void);
 void create_kmalloc_caches(slab_flags_t);
 
-/* Find the kmalloc slab corresponding for a certain size */
-struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags, unsigned long caller);
+extern u8 kmalloc_size_index[24];
+
+static inline unsigned int size_index_elem(unsigned int bytes)
+{
+	return (bytes - 1) / 8;
+}
+
+/*
+ * Find the kmem_cache structure that serves a given size of
+ * allocation
+ *
+ * This assumes size is larger than zero and not larger than
+ * KMALLOC_MAX_CACHE_SIZE and the caller must check that.
+ */
+static inline struct kmem_cache *
+kmalloc_slab(size_t size, gfp_t flags, unsigned long caller)
+{
+	unsigned int index;
+
+	if (size <= 192)
+		index = kmalloc_size_index[size_index_elem(size)];
+	else
+		index = fls(size - 1);
+
+	return kmalloc_caches[kmalloc_type(flags, caller)][index];
+}
 
 void *__kmem_cache_alloc_node(struct kmem_cache *s, gfp_t gfpflags,
 			      int node, size_t orig_size,