linux-kernel - [PATCH AUTOSEL for 4.9 146/190] mm: hwpoison: call shake_page() after try_to

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Date:   Thu, 8 Mar 2018 04:59:56 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Xiaolong Ye <xiaolong.ye@...el.com>,
        Chen Gong <gong.chen@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.9 146/190] mm: hwpoison: call shake_page() after
 try_to_unmap() for mlocked page

From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>

[ Upstream commit 286c469a988fbaf68e3a97ddf1e6c245c1446968 ]

Memory error handler calls try_to_unmap() for error pages in various
states.  If the error page is a mlocked page, error handling could fail
with "still referenced by 1 users" message.  This is because the page is
linked to and stays in lru cache after the following call chain.

  try_to_unmap_one
    page_remove_rmap
      clear_page_mlock
        putback_lru_page
          lru_cache_add

memory_failure() calls shake_page() to hanlde the similar issue, but
current code doesn't cover because shake_page() is called only before
try_to_unmap().  So this patches adds shake_page().

Fixes: 23a003bfd23ea9ea0b7756b920e51f64b284b468 ("mm/madvise: pass return code of memory_failure() to userspace")
Link: http://lkml.kernel.org/r/20170417055948.GM31394@yexl-desktop
Link: http://lkml.kernel.org/r/1493197841-23986-3-git-send-email-n-horiguchi@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Reported-by: kernel test robot <lkp@...el.com>
Cc: Xiaolong Ye <xiaolong.ye@...el.com>
Cc: Chen Gong <gong.chen@...ux.intel.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 mm/memory-failure.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 5aa71a82ca73..851efb004857 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -921,6 +921,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	int ret;
 	int kill = 1, forcekill;
 	struct page *hpage = *hpagep;
+	bool mlocked = PageMlocked(hpage);
 
 	/*
 	 * Here we are interested only in user-mapped pages, so skip any
@@ -984,6 +985,13 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 		pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
 		       pfn, page_mapcount(hpage));
 
+	/*
+	 * try_to_unmap() might put mlocked page in lru cache, so call
+	 * shake_page() again to ensure that it's flushed.
+	 */
+	if (mlocked)
+		shake_page(hpage, 0);
+
 	/*
 	 * Now that the dirty bit has been propagated to the
 	 * struct page and all unmaps done we can decide if
-- 
2.14.1