Commit 88d6ac40 authored Sep 06, 2017 by Wen Yang Committed by Linus Torvalds Sep 06, 2017

mm/vmstat: fix divide error at __fragmentation_index

When order is -1 or too big, *1UL << order* will be 0, which will cause
a divide error.  Although it seems that all callers of
__fragmentation_index() will only do so with a valid order, the patch
can make it more robust.

Should prevent reoccurrences of
https://bugzilla.kernel.org/show_bug.cgi?id=196555

Link: http://lkml.kernel.org/r/1501751520-2598-1-git-send-email-wen.yang99@zte.com.cn


Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Reviewed-by: Jiang Biao <jiang.biao2@zte.com.cn>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 79b63f12

mm/vmstat.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -870,6 +870,9 @@ static int __fragmentation_index(unsigned int order, struct contig_page_info *in
		{
		unsigned long requested = 1UL << order;

		if (WARN_ON_ONCE(order >= MAX_ORDER))
		return 0;

		if (!info->free_blocks_total)
		return 0;

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