[PATCH 17/32] GFS2: Improve bug trap code in ->releasepage()

From: Steven Whitehouse
Date: Thu May 19 2011 - 05:14:37 EST

If the buffer is dirty or pinned, then as well as printing a
warning, we should also refuse to release the page in

Currently this can occur if there is a race between mmap()ed
writers and O_DIRECT on the same file. With the addition of
->launder_page() in the future, we should be able to close
this gap.

Signed-off-by: Steven Whitehouse <swhiteho@xxxxxxxxxx>

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 0f5c4f9..802ac5e 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -1076,8 +1076,8 @@ int gfs2_releasepage(struct page *page, gfp_t gfp_mask)
bd = bh->b_private;
if (bd && bd->bd_ail)
goto cannot_release;
- gfs2_assert_warn(sdp, !buffer_pinned(bh));
- gfs2_assert_warn(sdp, !buffer_dirty(bh));
+ if (buffer_pinned(bh) || buffer_dirty(bh))
+ goto not_possible;
bh = bh->b_this_page;
} while(bh != head);
@@ -1107,6 +1107,10 @@ int gfs2_releasepage(struct page *page, gfp_t gfp_mask)
} while (bh != head);

return try_to_free_buffers(page);
+not_possible: /* Should never happen */
+ WARN_ON(buffer_dirty(bh));
+ WARN_ON(buffer_pinned(bh));
return 0;

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