Currently while allocating a slab for a offline node, we use its
associated node_numa_mem to search for a partial slab. If we don't find
a partial slab, we try allocating a slab from the offline node using
__alloc_pages_node. However this is bound to fail.

NIP [c00000000039a300] __alloc_pages_nodemask+0x130/0x3b0
LR [c00000000039a3c4] __alloc_pages_nodemask+0x1f4/0x3b0
Call Trace:
[c0000008b36837f0] [c00000000039a3b4] __alloc_pages_nodemask+0x1e4/0x3b0 (unreliable)
[c0000008b3683870] [c0000000003d1ff8] new_slab+0x128/0xcf0
[c0000008b3683950] [c0000000003d6060] ___slab_alloc+0x410/0x820
[c0000008b3683a40] [c0000000003d64a4] __slab_alloc+0x34/0x60
[c0000008b3683a70] [c0000000003d78b0] __kmalloc_node+0x110/0x490
[c0000008b3683af0] [c000000000343a08] kvmalloc_node+0x58/0x110
[c0000008b3683b30] [c0000000003ffd44] mem_cgroup_css_online+0x104/0x270
[c0000008b3683b90] [c000000000234e08] online_css+0x48/0xd0
[c0000008b3683bc0] [c00000000023dedc] cgroup_apply_control_enable+0x2ec/0x4d0
[c0000008b3683ca0] [c0000000002416f8] cgroup_mkdir+0x228/0x5f0
[c0000008b3683d10] [c000000000520360] kernfs_iop_mkdir+0x90/0xf0
[c0000008b3683d50] [c00000000043e400] vfs_mkdir+0x110/0x230
[c0000008b3683da0] [c000000000441ee0] do_mkdirat+0xb0/0x1a0
[c0000008b3683e20] [c00000000000b278] system_call+0x5c/0x68

Mitigate this by allocating the new slab from the node_numa_mem.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Sachin Sant <redacted>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Christopher Lameter <redacted>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Joonsoo Kim <redacted>
Cc: Kirill Tkhai <redacted>
Cc: Vlastimil Babka <redacted>
Cc: Srikar Dronamraju <redacted>
Cc: Bharata B Rao <redacted>
Cc: Nathan Lynch <redacted>

Reported-by: Sachin Sant <redacted>
Tested-by: Sachin Sant <redacted>
Signed-off-by: Srikar Dronamraju <redacted>
---
Changelog v1 -> v2:
- Handled comments from Vlastimil Babka
	- Now node gets set to node_numa_mem in new_slab_objects.

 mm/slub.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 1c55bf7892bf..2dc603a84290 100644
--- a/mm/slub.c
+++ b/mm/slub.c

@@ -2475,6 +2475,9 @@ static inline void *new_slab_objects(struct kmem_cache *s, gfp_t flags,
 	if (freelist)
 		return freelist;
 
+	if (node != NUMA_NO_NODE && !node_present_pages(node))
+		node = node_to_mem_node(node);
+
 	page = new_slab(s, flags, node);
 	if (page) {
 		c = raw_cpu_ptr(s->cpu_slab);

@@ -2569,12 +2572,10 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 redo:
 
 	if (unlikely(!node_match(page, node))) {
-		int searchnode = node;
-
 		if (node != NUMA_NO_NODE && !node_present_pages(node))
-			searchnode = node_to_mem_node(node);
+			node = node_to_mem_node(node);
 
-		if (unlikely(!node_match(page, searchnode))) {
+		if (unlikely(!node_match(page, node))) {
 			stat(s, ALLOC_NODE_MISMATCH);
 			deactivate_slab(s, page, c->freelist, c);
 			goto new_slab;

-- 
2.18.1