[PATCH] swap: redirty page if page write fails on swap file

[Jerome Marchand <jmarchan@redhat.com>]

Since commit 62c230b, swap_writepage() calls direct_IO on swap files.
However, in that case 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 <jmarchan@redhat.com>
---
 mm/page_io.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index 78eee32..04ca00d 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -222,6 +222,8 @@ 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;
 	}

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