mm: do not warn on offline nodes unless the specific node is explicitly requested

Oscar has noticed that we splat

   WARNING: CPU: 0 PID: 64 at ./include/linux/gfp.h:467 vmemmap_alloc_block+0x4e/0xc9
   [...]
   CPU: 0 PID: 64 Comm: kworker/u4:1 Tainted: G        W   E     4.17.0-rc5-next-20180517-1-default+ #66
   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014
   Workqueue: kacpi_hotplug acpi_hotplug_work_fn
   Call Trace:
    vmemmap_populate+0xf2/0x2ae
    sparse_mem_map_populate+0x28/0x35
    sparse_add_one_section+0x4c/0x187
    __add_pages+0xe7/0x1a0
    add_pages+0x16/0x70
    add_memory_resource+0xa3/0x1d0
    add_memory+0xe4/0x110
    acpi_memory_device_add+0x134/0x2e0
    acpi_bus_attach+0xd9/0x190
    acpi_bus_scan+0x37/0x70
    acpi_device_hotplug+0x389/0x4e0
    acpi_hotplug_work_fn+0x1a/0x30
    process_one_work+0x146/0x340
    worker_thread+0x47/0x3e0
    kthread+0xf5/0x130
    ret_from_fork+0x35/0x40

when adding memory to a node that is currently offline.

The VM_WARN_ON is just too loud without a good reason.  In this
particular case we are doing

	alloc_pages_node(node, GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN, order)

so we do not insist on allocating from the given node (it is more a
hint) so we can fall back to any other populated node and moreover we
explicitly ask to not warn for the allocation failure.

Soften the warning only to cases when somebody asks for the given node
explicitly by __GFP_THISNODE.

Link: http://lkml.kernel.org/r/20180523125555.30039-3-mhocko@kernel.orgSigned-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Oscar Salvador <osalvador@techadventures.net>
Tested-by: Oscar Salvador <osalvador@techadventures.net>
Reviewed-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/gfp.h

@@ -464,7 +464,7 @@ static inline struct page *
 __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
 {
 	VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
-	VM_WARN_ON(!node_online(nid));
+	VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid));
 
 	return __alloc_pages(gfp_mask, order, nid);
 }