dma_alloc_coherent: clean it up

This thing was rather stupidly coded.  Rework it all prior to making
changes.

Also, rename local variable `page': kernel readers expect something called
`page' to have type `struct page *'.

Cc: Guennadi Liakhovetski <lg@denx.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Dmitry Baryshkov <dbaryshkov@gmail.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 29 insertions, 25 deletions

diff --git a/kernel/dma-coherent.c b/kernel/dma-coherent.c
index 4bdcea822b45..8056d081609c 100644
--- a/kernel/dma-coherent.c
+++ b/kernel/dma-coherent.c
@@ -109,34 +109,38 @@ EXPORT_SYMBOL(dma_mark_declared_memory_occupied);
 int dma_alloc_from_coherent(struct device *dev, ssize_t size,
                                        dma_addr_t *dma_handle, void **ret)
 {
-        struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL;
+        struct dma_coherent_mem *mem;
         int order = get_order(size);
+        int pageno;
 
-        if (mem) {
-                int page = bitmap_find_free_region(mem->bitmap, mem->size,
-                                                     order);
-                if (page >= 0) {
-                        /*
-                         * Memory was found in the per-device arena.
-                         */
-                        *dma_handle = mem->device_base + (page << PAGE_SHIFT);
-                        *ret = mem->virt_base + (page << PAGE_SHIFT);
-                        memset(*ret, 0, size);
-                } else if (mem->flags & DMA_MEMORY_EXCLUSIVE) {
-                        /*
-                         * The per-device arena is exhausted and we are not
-                         * permitted to fall back to generic memory.
-                         */
-                        *ret = NULL;
-                } else {
-                        /*
-                         * The per-device arena is exhausted and we are
-                         * permitted to fall back to generic memory.
-                         */
-                         return 0;
-                }
+        if (!dev)
+                return 0;
+        mem = dev->dma_mem;
+        if (!mem)
+                return 0;
+
+        pageno = bitmap_find_free_region(mem->bitmap, mem->size, order);
+        if (pageno >= 0) {
+                /*
+                 * Memory was found in the per-device arena.
+                 */
+                *dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
+                *ret = mem->virt_base + (pageno << PAGE_SHIFT);
+                memset(*ret, 0, size);
+        } else if (mem->flags & DMA_MEMORY_EXCLUSIVE) {
+                /*
+                 * The per-device arena is exhausted and we are not
+                 * permitted to fall back to generic memory.
+                 */
+                *ret = NULL;
+        } else {
+                /*
+                 * The per-device arena is exhausted and we are
+                 * permitted to fall back to generic memory.
+                 */
+                 return 0;
         }
-        return (mem != NULL);
+        return 1;
 }
 EXPORT_SYMBOL(dma_alloc_from_coherent);