mm/slab: clean up cache type determination

Current cache type determination code is open-code and looks not
understandable.  Following patch will introduce one more cache type and
it would make code more complex.  So, before it happens, this patch
abstracts these codes.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 71 insertions, 34 deletions

diff --git a/mm/slab.c b/mm/slab.c
index d5dffc806f82..9b56685fb79b 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2023,6 +2023,64 @@ __kmem_cache_alias(const char *name, size_t size, size_t align,
         return cachep;
 }
 
+static bool set_off_slab_cache(struct kmem_cache *cachep,
+                        size_t size, unsigned long flags)
+{
+        size_t left;
+
+        cachep->num = 0;
+
+        /*
+         * Determine if the slab management is 'on' or 'off' slab.
+         * (bootstrapping cannot cope with offslab caches so don't do
+         * it too early on. Always use on-slab management when
+         * SLAB_NOLEAKTRACE to avoid recursive calls into kmemleak)
+         */
+        if (size < OFF_SLAB_MIN_SIZE)
+                return false;
+
+        if (slab_early_init)
+                return false;
+
+        if (flags & SLAB_NOLEAKTRACE)
+                return false;
+
+        /*
+         * Size is large, assume best to place the slab management obj
+         * off-slab (should allow better packing of objs).
+         */
+        left = calculate_slab_order(cachep, size, flags | CFLGS_OFF_SLAB);
+        if (!cachep->num)
+                return false;
+
+        /*
+         * If the slab has been placed off-slab, and we have enough space then
+         * move it on-slab. This is at the expense of any extra colouring.
+         */
+        if (left >= cachep->num * sizeof(freelist_idx_t))
+                return false;
+
+        cachep->colour = left / cachep->colour_off;
+
+        return true;
+}
+
+static bool set_on_slab_cache(struct kmem_cache *cachep,
+                        size_t size, unsigned long flags)
+{
+        size_t left;
+
+        cachep->num = 0;
+
+        left = calculate_slab_order(cachep, size, flags);
+        if (!cachep->num)
+                return false;
+
+        cachep->colour = left / cachep->colour_off;
+
+        return true;
+}
+
 /**
  * __kmem_cache_create - Create a cache.
  * @cachep: cache management descriptor
@@ -2047,7 +2105,6 @@ __kmem_cache_alias(const char *name, size_t size, size_t align,
 int
 __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 {
-        size_t left_over, freelist_size;
         size_t ralign = BYTES_PER_WORD;
         gfp_t gfp;
         int err;
@@ -2098,6 +2155,10 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
          * 4) Store it.
          */
         cachep->align = ralign;
+        cachep->colour_off = cache_line_size();
+        /* Offset must be a multiple of the alignment. */
+        if (cachep->colour_off < cachep->align)
+                cachep->colour_off = cachep->align;
 
         if (slab_is_available())
                 gfp = GFP_KERNEL;
@@ -2152,43 +2213,18 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
         }
 #endif
 
-        /*
-         * Determine if the slab management is 'on' or 'off' slab.
-         * (bootstrapping cannot cope with offslab caches so don't do
-         * it too early on. Always use on-slab management when
-         * SLAB_NOLEAKTRACE to avoid recursive calls into kmemleak)
-         */
-        if (size >= OFF_SLAB_MIN_SIZE && !slab_early_init &&
-            !(flags & SLAB_NOLEAKTRACE)) {
-                /*
-                 * Size is large, assume best to place the slab management obj
-                 * off-slab (should allow better packing of objs).
-                 */
+        if (set_off_slab_cache(cachep, size, flags)) {
                 flags |= CFLGS_OFF_SLAB;
+                goto done;
         }
 
-        left_over = calculate_slab_order(cachep, size, flags);
-
-        if (!cachep->num)
-                return -E2BIG;
-
-        freelist_size = cachep->num * sizeof(freelist_idx_t);
+        if (set_on_slab_cache(cachep, size, flags))
+                goto done;
 
-        /*
-         * If the slab has been placed off-slab, and we have enough space then
-         * move it on-slab. This is at the expense of any extra colouring.
-         */
-        if (flags & CFLGS_OFF_SLAB && left_over >= freelist_size) {
-                flags &= ~CFLGS_OFF_SLAB;
-                left_over -= freelist_size;
-        }
+        return -E2BIG;
 
-        cachep->colour_off = cache_line_size();
-        /* Offset must be a multiple of the alignment. */
-        if (cachep->colour_off < cachep->align)
-                cachep->colour_off = cachep->align;
-        cachep->colour = left_over / cachep->colour_off;
-        cachep->freelist_size = freelist_size;
+done:
+        cachep->freelist_size = cachep->num * sizeof(freelist_idx_t);
         cachep->flags = flags;
         cachep->allocflags = __GFP_COMP;
         if (CONFIG_ZONE_DMA_FLAG && (flags & SLAB_CACHE_DMA))
@@ -2209,7 +2245,8 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 #endif
 
         if (OFF_SLAB(cachep)) {
-                cachep->freelist_cache = kmalloc_slab(freelist_size, 0u);
+                cachep->freelist_cache =
+                        kmalloc_slab(cachep->freelist_size, 0u);
                 /*
                  * This is a possibility for one of the kmalloc_{dma,}_caches.
                  * But since we go off slab only for object size greater than