[patch 13/20] mm, meminit: ensure node is online before checking whether pages are uninitialised

[patch 13/20] mm, meminit: ensure node is online before checking whether pages are uninitialised

[akpm]

From: Mel Gorman <mgorman@techsingularity.net>
Subject: mm, meminit: ensure node is online before checking whether pages are uninitialised

early_page_uninitialised looks up an arbitrary PFN.  While a machine
without node 0 will boot with "mm, page_alloc: Always return a valid node
from early_pfn_to_nid", it works because it assumes that nodes are always
in PFN order.  This is not guaranteed so this patch adds robustness by
always checking if the node being checked is online.

Link: http://lkml.kernel.org/r/1468008031-3848-4-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: David Rientjes <rientjes@google.com>
Cc: <stable@vger.kernel.org>	[4.2+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff -puN mm/page_alloc.c~mm-meminit-ensure-node-is-online-before-checking-whether-pages-are-uninitialised mm/page_alloc.c
--- a/mm/page_alloc.c~mm-meminit-ensure-node-is-online-before-checking-whether-pages-are-uninitialised
+++ a/mm/page_alloc.c
@@ -286,7 +286,9 @@ static inline void reset_deferred_memini
 /* Returns true if the struct page for the pfn is uninitialised */
 static inline bool __meminit early_page_uninitialised(unsigned long pfn)
 {
-	if (pfn >= NODE_DATA(early_pfn_to_nid(pfn))->first_deferred_pfn)
+	int nid = early_pfn_to_nid(pfn);
+
+	if (node_online(nid) && pfn >= NODE_DATA(nid)->first_deferred_pfn)
 		return true;
 
 	return false;
_