x86, pci-dma.c: don't always add __GFP_NORETRY to gfp

Currently arch/x86/kernel/pci-dma.c always adds __GFP_NORETRY
to the allocation flags, because it wants to be reasonably
sure not to deadlock when calling alloc_pages().

But really that should only be done in two cases:
- when allocating memory in the lower 16 MB DMA zone.
  If there's no free memory there, waiting or OOM killing is of no use
- when optimistically trying an allocation in the DMA32 zone
  when dma_mask < DMA_32BIT_MASK hoping that the allocation
  happens to fall within the limits of the dma_mask

Also blindly adding __GFP_NORETRY to the the gfp variable might
not be a good idea since we then also use it when calling
dma_ops->alloc_coherent(). Clearing it might also not be a
good idea, dma_alloc_coherent()'s caller might have set it
on purpose. The gfp variable should not be clobbered.

[ mingo@elte.hu: converted to delta patch ontop of previous version. ]

Signed-off-by: Miquel van Smoorenburg <miquels@cistron.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 069e843..dc00a13 100644 (file)
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -378,6 +378,7 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
        struct page *page;
        unsigned long dma_mask = 0;
        dma_addr_t bus;
+       int noretry = 0;
 
        /* ignore region specifiers */
        gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
@@ -397,19 +398,25 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
        if (dev->dma_mask == NULL)
                return NULL;
 
+       /* Don't invoke OOM killer or retry in lower 16MB DMA zone */
+       if (gfp & __GFP_DMA)
+               noretry = 1;
+
 #ifdef CONFIG_X86_64
        /* 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 <= DMA_32BIT_MASK && !(gfp & GFP_DMA))
+       if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA)) {
                gfp |= GFP_DMA32;
+               if (dma_mask < DMA_32BIT_MASK)
+                       noretry = 1;
+       }
 #endif
 
  again:
-       /* Don't invoke OOM killer or retry in lower 16MB DMA zone */
        page = dma_alloc_pages(dev,
-               (gfp & GFP_DMA) ? gfp | __GFP_NORETRY : gfp, get_order(size));
+               noretry ? gfp | __GFP_NORETRY : gfp, get_order(size));
        if (page == NULL)
                return NULL;