mm, meminit: ensure node is online before checking whether pages are uninitialised

commit ef70b6f41cda6270165a6f27b2548ed31cfa3cb2 upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ce9d0d47ddc09f0e3b390a6e0ee6c3a17e8afcd9..2bcdfbf8c36d9a3c7fab44a553d62507c4d811cf 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -275,7 +275,9 @@ 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;