Patch "mm: hwpoison: call shake_page() after try_to_unmap() for mlocked page" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

mm: hwpoison: call shake_page() after try_to_unmap() for mlocked page

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mm-hwpoison-call-shake_page-after-try_to_unmap-for-mlocked-page.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Naoya Horiguchi <[email protected]>
Date: Wed, 3 May 2017 14:56:22 -0700
Subject: mm: hwpoison: call shake_page() after try_to_unmap() for mlocked page

From: Naoya Horiguchi <[email protected]>

[ 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().

---
 mm/memory-failure.c |    8 ++++++++
 1 file changed, 8 insertions(+)

@@ -921,6 +921,7 @@ static int hwpoison_user_mappings(struct
 	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

@@ -985,6 +986,13 @@ static int hwpoison_user_mappings(struct
 		       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
 	 * killing is needed or not.  Only kill when the page

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/mm-hwpoison-call-shake_page-after-try_to_unmap-for-mlocked-page.patch