[PATCH] fs: Don't clear dirty bits in block_write_full_page()

[Jan Kara]

If getblock() fails in block_write_full_page(), we don't want to clear
dirty bits on buffers. Actually, we even want to redirty the page. This
way we just won't silently discard users data (written e.g. through mmap)
in case of ENOSPC, EDQUOT, EIO or other write error. The downside of this
approach is that if the error is persistent we have this page pinned in
memory forever and if there are lots of such pages, we can bring the
machine OOM.

Signed-off-by: Jan Kara <jack@xxxxxxx>
---
 fs/buffer.c |   10 +++-------
 1 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 891e1c7..ae779a0 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1833,9 +1833,11 @@ recover:
 	/*
 	 * ENOSPC, or some other error.  We may already have added some
 	 * blocks to the file, so we need to write these out to avoid
-	 * exposing stale data.
+	 * exposing stale data. We redirty the page so that we don't
+	 * loose data we are unable to write.
 	 * The page is currently locked and not marked for writeback
 	 */
+	redirty_page_for_writepage(wbc, page);
 	bh = head;
 	/* Recovery: lock and submit the mapped buffers */
 	do {
@@ -1843,12 +1845,6 @@ recover:
 		    !buffer_delay(bh)) {
 			lock_buffer(bh);
 			mark_buffer_async_write(bh);
-		} else {
-			/*
-			 * The buffer may have been set dirty during
-			 * attachment to a dirty page.
-			 */
-			clear_buffer_dirty(bh);
 		}
 	} while ((bh = bh->b_this_page) != head);
 	SetPageError(page);
-- 
1.6.0.2

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