From: Wu Fengguang <fengguang.wu@intel.com>
Date: Wed, 16 Dec 2009 11:19:58 +0000 (+0100)
Subject: HWPOISON: comment the possible set_page_dirty() race
X-Git-Tag: v2.6.33-rc1~45^2~25
X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=db0480b3a61bd6ad86ead3b8bbad094ab0996932

HWPOISON: comment the possible set_page_dirty() race

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b62287d..dc47415 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -687,6 +687,8 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	/*
 	 * Propagate the dirty bit from PTEs to struct page first, because we
 	 * need this to decide if we should kill or just drop the page.
+	 * XXX: the dirty test could be racy: set_page_dirty() may not always
+	 * be called inside page lock (it's recommended but not enforced).
 	 */
 	mapping = page_mapping(p);
 	if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {