powerpc/perf: Add ___GFP_NOWARN flag to alloc_pages_node()

Stack trace output during a stress test:
 [    4.310049] Freeing initrd memory: 22592K
[    4.310646] rtas_flash: no firmware flash support
[    4.313341] cpuhp/64: page allocation failure: order:0, mode:0x14480c0(GFP_KERNEL|__GFP_ZERO|__GFP_THISNODE), nodemask=(null)
[    4.313465] cpuhp/64 cpuset=/ mems_allowed=0
[    4.313521] CPU: 64 PID: 392 Comm: cpuhp/64 Not tainted 4.11.0-39.el7a.ppc64le #1
[    4.313588] Call Trace:
[    4.313622] [c000000f1fb1b8e0] [c000000000c09388] dump_stack+0xb0/0xf0 (unreliable)
[    4.313694] [c000000f1fb1b920] [c00000000030ef6c] warn_alloc+0x12c/0x1c0
[    4.313753] [c000000f1fb1b9c0] [c00000000030ff68] __alloc_pages_nodemask+0xea8/0x1000
[    4.313823] [c000000f1fb1bbb0] [c000000000113a8c] core_imc_mem_init+0xbc/0x1c0
[    4.313892] [c000000f1fb1bc00] [c000000000113cdc] ppc_core_imc_cpu_online+0x14c/0x170
[    4.313962] [c000000f1fb1bc90] [c000000000125758] cpuhp_invoke_callback+0x198/0x5d0
[    4.314031] [c000000f1fb1bd00] [c00000000012782c] cpuhp_thread_fun+0x8c/0x3d0
[    4.314101] [c000000f1fb1bd60] [c0000000001678d0] smpboot_thread_fn+0x290/0x2a0
[    4.314169] [c000000f1fb1bdc0] [c00000000015ee78] kthread+0x168/0x1b0
[    4.314229] [c000000f1fb1be30] [c00000000000b368] ret_from_kernel_thread+0x5c/0x74
[    4.314313] Mem-Info:
[    4.314356] active_anon:0 inactive_anon:0 isolated_anon:0

core_imc_mem_init() at system boot use alloc_pages_node() to get memory
and alloc_pages_node() throws this stack dump when tried to allocate
memory from a node which has no memory behind it. Add a ___GFP_NOWARN
flag in allocation request as a fix.
Signed-off-by: NAnju T Sudhakar <anju@linux.vnet.ibm.com>
Reported-by: NMichael Ellerman <mpe@ellerman.id.au>
Reported-by: NVenkat R.B <venkatb3@in.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

arch/powerpc/perf/imc-pmu.c

@@ -537,8 +537,8 @@ static int core_imc_mem_init(int cpu, int size)
 
 	/* We need only vbase for core counters */
 	mem_info->vbase = page_address(alloc_pages_node(phys_id,
-					  GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
-					  get_order(size)));
+					  GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE |
+					  __GFP_NOWARN, get_order(size)));
 	if (!mem_info->vbase)
 		return -ENOMEM;
 
@@ -791,8 +791,8 @@ static int thread_imc_mem_alloc(int cpu_id, int size)
 		 * free the memory in cpu offline path.
 		 */
 		local_mem = page_address(alloc_pages_node(phys_id,
-				  GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
-				  get_order(size)));
+				  GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE |
+				  __GFP_NOWARN, get_order(size)));
 		if (!local_mem)
 			return -ENOMEM;