1 files changed, 31 insertions, 11 deletions

diff --git a/kernel/dma-coherent.c b/kernel/dma-coherent.c
index f013a0c2e111..038707404b76 100644
--- a/kernel/dma-coherent.c
+++ b/kernel/dma-coherent.c
@@ -109,20 +109,40 @@ 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) {
-                        *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)
-                        *ret = NULL;
+        if (!dev)
+                return 0;
+        mem = dev->dma_mem;
+        if (!mem)
+                return 0;
+        if (unlikely(size > mem->size))
+                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);