Commit e570f56c authored May 20, 2016 by Naoya Horiguchi Committed by Linus Torvalds May 20, 2016

mm: check_new_page_bad() directly returns in __PG_HWPOISON case

Currently we check page->flags twice for "HWPoisoned" case of
check_new_page_bad(), which can cause a race with unpoisoning.

This race unnecessarily taints kernel with "BUG: Bad page state".
check_new_page_bad() is the only caller of bad_page() which is
interested in __PG_HWPOISON, so let's move the hwpoison related code in
bad_page() to it.

Link: http://lkml.kernel.org/r/20160518100949.GA17299@hori1.linux.bs1.fc.nec.co.jp


Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 29b52de1

mm/page_alloc.c

+3 −6

Original line number	Diff line number	Diff line
		@@ -522,12 +522,6 @@ static void bad_page(struct page page, const char reason,
		static unsigned long nr_shown;
		static unsigned long nr_unshown;

		/* Don't complain about poisoned pages */
		if (PageHWPoison(page)) {
		page_mapcount_reset(page); /* remove PageBuddy */
		return;
		}

		/*
		* Allow a burst of 60 reports, then keep quiet for that minute;
		* or allow a steady drip of one report per second.
		@@ -1654,6 +1648,9 @@ static void check_new_page_bad(struct page *page)
		if (unlikely(page->flags & __PG_HWPOISON)) {
		bad_reason = "HWPoisoned (hardware-corrupted)";
		bad_flags = __PG_HWPOISON;
		/* Don't complain about hwpoisoned pages */
		page_mapcount_reset(page); /* remove PageBuddy */
		return;
		}
		if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
		bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";

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