GFS2: Improve bug trap code in ->releasepage()

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

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@redhat.com>

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 0f5c4f9d5d62beee06937a8d0c98bd015f7dc5ee..802ac5eeba28e2c77c8618ba457a179fa8babb73 100644 (file)
--- 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);
        gfs2_log_unlock(sdp);
@@ -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));
 cannot_release:
        gfs2_log_unlock(sdp);
        return 0;