[PATCH] x86_64: Use the DMA32 zone for dma_alloc_coherent()/pci_alloc_consistent

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/arch/x86_64/kernel/pci-gart.c b/arch/x86_64/kernel/pci-gart.c
index 88be97c96987..2e28e855ec3c 100644
--- a/arch/x86_64/kernel/pci-gart.c
+++ b/arch/x86_64/kernel/pci-gart.c
@@ -220,6 +220,12 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
            uses the normal dma_mask for alloc_coherent. */
         dma_mask &= *dev->dma_mask;
 
+        /* Why <=? Even when the mask is smaller than 4GB it is often larger 
+           than 16MB and in this case we have a chance of finding fitting memory 
+           in the next higher zone first. If not retry with true GFP_DMA. -AK */
+        if (dma_mask <= 0xffffffff)
+                gfp |= GFP_DMA32;
+
  again:
         memory = dma_alloc_pages(dev, gfp, get_order(size));
         if (memory == NULL)
@@ -245,7 +251,7 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
                                 }
 
                                 if (!(gfp & GFP_DMA)) { 
-                                        gfp |= GFP_DMA; 
+                                        gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
                                         goto again;
                                 }
                                 return NULL;