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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5d013526bd0a035a4816067bc12867f81e4e8e19..8b3e1341b7544608cac4777a37bbd424432488e1 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -286,7 +286,9 @@ static inline void reset_deferred_meminit(pg_data_t *pgdat)
 /* 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;