[PATCH 2/3] x86, swiotlb: Try coherent allocations with __GFP_NOWARN

[Joerg Roedel]

From: Joerg Roedel <jroedel@xxxxxxx>

When we boot a kdump kernel in high memory, there is by
default only 72MB of low memory available. The swiotlb code
takes 64MB of it (by default) so that there are only 8MB
left to allocate from. On systems with many devices this
causes page allocator warnings from dma_generic_alloc_coherent():

systemd-udevd: page allocation failure: order:0, mode:0x280d4
CPU: 0 PID: 197 Comm: systemd-udevd Tainted: G        W       3.12.28-4-default #1
Hardware name: HP ProLiant DL980 G7, BIOS P66 07/30/2012
 ffff8800781335e0 ffffffff8150b1db 00000000000280d4 ffffffff8113af90
 0000000000000000 0000000000000000 ffff88007efdbb00 0000000100000000
 0000000000000000 0000000000000000 0000000000000000 0000000000000001
Call Trace:
  dump_trace+0x7d/0x2d0
  show_stack_log_lvl+0x94/0x170
  show_stack+0x21/0x50
  dump_stack+0x41/0x51
  warn_alloc_failed+0xf0/0x160
  __alloc_pages_slowpath+0x72f/0x796
  __alloc_pages_nodemask+0x1ea/0x210
  dma_generic_alloc_coherent+0x96/0x140
  x86_swiotlb_alloc_coherent+0x1c/0x50
  ttm_dma_pool_alloc_new_pages+0xab/0x320 [ttm]
  ttm_dma_populate+0x3ce/0x640 [ttm]
  ttm_tt_bind+0x36/0x60 [ttm]
  ttm_bo_handle_move_mem+0x55f/0x5c0 [ttm]
  ttm_bo_move_buffer+0x105/0x130 [ttm]
  ttm_bo_validate+0xc1/0x130 [ttm]
  ttm_bo_init+0x24b/0x400 [ttm]
  radeon_bo_create+0x16c/0x200 [radeon]
  radeon_ring_init+0x11e/0x2b0 [radeon]
  r100_cp_init+0x123/0x5b0 [radeon]
  r100_startup+0x194/0x230 [radeon]
  r100_init+0x223/0x410 [radeon]
  radeon_device_init+0x6af/0x830 [radeon]
  radeon_driver_load_kms+0x89/0x180 [radeon]
  drm_get_pci_dev+0x121/0x2f0 [drm]
  local_pci_probe+0x39/0x60
  pci_device_probe+0xa9/0x120
  driver_probe_device+0x9d/0x3d0
  __driver_attach+0x8b/0x90
  bus_for_each_dev+0x5b/0x90
  bus_add_driver+0x1f8/0x2c0
  driver_register+0x5b/0xe0
  do_one_initcall+0xf2/0x1a0
  load_module+0x1207/0x1c70
  SYSC_finit_module+0x75/0xa0
  system_call_fastpath+0x16/0x1b
  0x7fac533d2788

After these warnings the code enters a fall-back path and
allocated directly from the swiotlb aperture in the end.
So remove these warnings as this is not a fatal error.

Acked-by: Baoquan He <bhe@xxxxxxxxxx>
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
---
 arch/x86/kernel/pci-swiotlb.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index 77dd0ad..6d6894c 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -20,6 +20,13 @@ void *x86_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
 {
 	void *vaddr;
 
+	/*
+         * Don't print a warning when the first allocation attempt
+         * fails. The swiotlb_alloc_coherent() function will print a
+         * warning when the allocation of DMA memory ultimatly failed.
+	 */
+	flags |= __GFP_NOWARN;
+
 	vaddr = dma_generic_alloc_coherent(hwdev, size, dma_handle, flags,
 					   attrs);
 	if (vaddr)
-- 
1.9.1

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