sfc: Allocate DMA and event rings using GFP_KERNEL

Currently we allocate DMA descriptor rings and event rings using
pci_alloc_consistent() which selects non-blocking behaviour from the
page allocator (GFP_ATOMIC). This is unnecessary, and since we
currently allocate a single contiguous block for each ring (up to 32
pages!) these allocations are likely to fail if there is any
significant memory pressure.  Use dma_alloc_coherent() and GFP_KERNEL
instead.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/sfc/nic.c

@@ -263,8 +263,8 @@ static int efx_alloc_special_buffer(struct efx_nic *efx,
 {
 	len = ALIGN(len, EFX_BUF_SIZE);
 
-	buffer->addr = pci_alloc_consistent(efx->pci_dev, len,
-					    &buffer->dma_addr);
+	buffer->addr = dma_alloc_coherent(&efx->pci_dev->dev, len,
+					  &buffer->dma_addr, GFP_KERNEL);
 	if (!buffer->addr)
 		return -ENOMEM;
 	buffer->len = len;
@@ -301,8 +301,8 @@ efx_free_special_buffer(struct efx_nic *efx, struct efx_special_buffer *buffer)
 		  (u64)buffer->dma_addr, buffer->len,
 		  buffer->addr, (u64)virt_to_phys(buffer->addr));
 
-	pci_free_consistent(efx->pci_dev, buffer->len, buffer->addr,
-			    buffer->dma_addr);
+	dma_free_coherent(&efx->pci_dev->dev, buffer->len, buffer->addr,
+			  buffer->dma_addr);
 	buffer->addr = NULL;
 	buffer->entries = 0;
 }