mem-hotplug: don't clear the only node in new_node_page()

Commit 394e31d2ceb4 ("mem-hotplug: alloc new page from a nearest
neighbor node when mem-offline") introduced new_node_page() for memory
hotplug.

In new_node_page(), the nid is cleared before calling
__alloc_pages_nodemask().  But if it is the only node of the system, and
the first round allocation fails, it will not be able to get memory from
an empty nodemask, and will trigger oom.

The patch checks whether it is the last node on the system, and if it
is, then don't clear the nid in the nodemask.

Fixes: 394e31d2ceb4 ("mem-hotplug: alloc new page from a nearest neighbor node when mem-offline")
Link: http://lkml.kernel.org/r/1473044391.4250.19.camel@TP420
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Reported-by: John Allen <jallen@linux.vnet.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 41266dc29f33fb1278d7e4e9d6fd2efab69380a1..b58906b6215cbb3d2b43abbcdb758e0809c42c7f 100644 (file)
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1567,7 +1567,9 @@ static struct page *new_node_page(struct page *page, unsigned long private,
                return alloc_huge_page_node(page_hstate(compound_head(page)),
                                        next_node_in(nid, nmask));
 
-       node_clear(nid, nmask);
+       if (nid != next_node_in(nid, nmask))
+               node_clear(nid, nmask);
+
        if (PageHighMem(page)
            || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
                gfp_mask |= __GFP_HIGHMEM;