SLUB: extract dma_kmalloc_cache from get_cache.

The rarely used dma functionality in get_slab() makes the function too
complex.  The compiler begins to spill variables from the working set onto the
stack.  The created function is only used in extremely rare cases so make sure
that the compiler does not decide on its own to merge it back into get_slab().

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 36 insertions, 30 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 55b508df62a3..2b50b97a0fc3 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2272,6 +2272,40 @@ panic:
         panic("Creation of kmalloc slab %s size=%d failed.\n", name, size);
 }
 
+#ifdef CONFIG_ZONE_DMA
+static noinline struct kmem_cache *dma_kmalloc_cache(int index, gfp_t flags)
+{
+        struct kmem_cache *s;
+        struct kmem_cache *x;
+        char *text;
+        size_t realsize;
+
+        s = kmalloc_caches_dma[index];
+        if (s)
+                return s;
+
+        /* Dynamically create dma cache */
+        x = kmalloc(kmem_size, flags & ~SLUB_DMA);
+        if (!x)
+                panic("Unable to allocate memory for dma cache\n");
+
+        if (index <= KMALLOC_SHIFT_HIGH)
+                realsize = 1 << index;
+        else {
+                if (index == 1)
+                        realsize = 96;
+                else
+                        realsize = 192;
+        }
+
+        text = kasprintf(flags & ~SLUB_DMA, "kmalloc_dma-%d",
+                        (unsigned int)realsize);
+        s = create_kmalloc_cache(x, text, realsize, flags);
+        kmalloc_caches_dma[index] = s;
+        return s;
+}
+#endif
+
 static struct kmem_cache *get_slab(size_t size, gfp_t flags)
 {
         int index = kmalloc_index(size);
@@ -2284,36 +2318,8 @@ static struct kmem_cache *get_slab(size_t size, gfp_t flags)
                 return NULL;
 
 #ifdef CONFIG_ZONE_DMA
-        if ((flags & SLUB_DMA)) {
-                struct kmem_cache *s;
-                struct kmem_cache *x;
-                char *text;
-                size_t realsize;
-
-                s = kmalloc_caches_dma[index];
-                if (s)
-                        return s;
-
-                /* Dynamically create dma cache */
-                x = kmalloc(kmem_size, flags & ~SLUB_DMA);
-                if (!x)
-                        panic("Unable to allocate memory for dma cache\n");
-
-                if (index <= KMALLOC_SHIFT_HIGH)
-                        realsize = 1 << index;
-                else {
-                        if (index == 1)
-                                realsize = 96;
-                        else
-                                realsize = 192;
-                }
-
-                text = kasprintf(flags & ~SLUB_DMA, "kmalloc_dma-%d",
-                                (unsigned int)realsize);
-                s = create_kmalloc_cache(x, text, realsize, flags);
-                kmalloc_caches_dma[index] = s;
-                return s;
-        }
+        if ((flags & SLUB_DMA))
+                return dma_kmalloc_cache(index, flags);
 #endif
         return &kmalloc_caches[index];
 }