[PATCH v2] dma-buf: system_heap: do not warn for costly allocation

[Minchan Kim]

Dmabuf system_heap allocation logic starts with the highest necessary
allocation order before falling back to lower orders. The requested
order can be higher than PAGE_ALLOC_COSTLY_ODER and failures to
allocate will flood dmesg with warnings. Such high-order allocations
are not unexpected and are handled by the system_heap's allocation
fallback mechanism.
Prevent these warnings when allocating higher than
PAGE_ALLOC_COSTLY_ODER pages using __GFP_NOWARN flag.

Below is ION warning example I got but dmabuf system heap is nothing different:

[ 1233.911533][  T460] warn_alloc: 11 callbacks suppressed
[ 1233.911539][  T460] allocator@2.0-s: page allocation failure: order:4, mode:0x140dc2(GFP_HIGHUSER|__GFP_COMP|__GFP_ZERO), nodemask=(null),cpuset=/,mems_allowed=0
[ 1233.926235][  T460] Call trace:
[ 1233.929370][  T460]  dump_backtrace+0x0/0x1d8
[ 1233.933704][  T460]  show_stack+0x18/0x24
[ 1233.937701][  T460]  dump_stack+0xc0/0x140
[ 1233.941783][  T460]  warn_alloc+0xf4/0x148
[ 1233.945862][  T460]  __alloc_pages_slowpath+0x9fc/0xa10
[ 1233.951101][  T460]  __alloc_pages_nodemask+0x278/0x2c0
[ 1233.956285][  T460]  ion_page_pool_alloc+0xd8/0x100
[ 1233.961144][  T460]  ion_system_heap_allocate+0xbc/0x2f0
[ 1233.966440][  T460]  ion_buffer_create+0x68/0x274
[ 1233.971130][  T460]  ion_buffer_alloc+0x8c/0x110
[ 1233.975733][  T460]  ion_dmabuf_alloc+0x44/0xe8
[ 1233.980248][  T460]  ion_ioctl+0x100/0x320
[ 1233.984332][  T460]  __arm64_sys_ioctl+0x90/0xc8
[ 1233.988934][  T460]  el0_svc_common+0x9c/0x168
[ 1233.993360][  T460]  do_el0_svc+0x1c/0x28
[ 1233.997358][  T460]  el0_sync_handler+0xd8/0x250
[ 1234.001989][  T460]  el0_sync+0x148/0x180

Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
* from v1 - https://lore.kernel.org/lkml/20210210162632.3903128-1-minchan@xxxxxxxxxx/
 * better description - surenb
 * use mid_order_gfp - john.stultz

 drivers/dma-buf/heaps/system_heap.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 29e49ac17251..e5f545ada587 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -40,11 +40,16 @@ struct dma_heap_attachment {
 	bool mapped;
 };
 
+#define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO | __GFP_COMP)
+/* 
+ * Avoid warning on order-4 allocation failures as we'll fall back to
+ * order-0 in that case.
+ */
+#define MID_ORDER_GFP (LOW_ORDER_GFP | __GFP_NOWARN)
 #define HIGH_ORDER_GFP  (((GFP_HIGHUSER | __GFP_ZERO | __GFP_NOWARN \
 				| __GFP_NORETRY) & ~__GFP_RECLAIM) \
 				| __GFP_COMP)
-#define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO | __GFP_COMP)
-static gfp_t order_flags[] = {HIGH_ORDER_GFP, LOW_ORDER_GFP, LOW_ORDER_GFP};
+static gfp_t order_flags[] = {HIGH_ORDER_GFP, MID_ORDER_GFP, LOW_ORDER_GFP};
 /*
  * The selection of the orders used for allocation (1MB, 64K, 4K) is designed
  * to match with the sizes often found in IOMMUs. Using order 4 pages instead
-- 
2.30.0.478.g8a0d178c01-goog