commit: 2d30d31ea3c5be426ce25607b9bd1835acb85e0a
From: Jerome Marchand <[email protected]>
Date: Mon, 29 Apr 2013 15:08:47 -0700
Subject: swap: redirty page if page write fails on swap file

Since commit 62c230bc1790 ("mm: add support for a filesystem to activate
swap files and use direct_IO for writing swap pages"), swap_writepage()
calls direct_IO on swap files.  However, in that case the page isn't
redirtied if I/O fails, and is therefore handled afterwards as if it has
been successfully written to the swap file, leading to memory corruption
when the page is eventually swapped back in.

This patch sets the page dirty when direct_IO() fails.  It fixes a
memory corruption that happened while using swap-over-NFS.

Signed-off-by: Jerome Marchand <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: <[email protected]>    [3.6+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
---
 mm/page_io.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/page_io.c b/mm/page_io.c
index 8e0e5c0..eb3300f 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -231,6 +231,8 @@ int __swap_writepage(struct page *page, struct 
writeback_control *wbc,
                if (ret == PAGE_SIZE) {
                        count_vm_event(PSWPOUT);
                        ret = 0;
+               } else {
+                       set_page_dirty(page);
                }
                return ret;
        }
-- 
1.7.10.4
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