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>

1 files changed, 6 insertions, 2 deletions

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 0f5c4f9d5d62..802ac5eeba28 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);
         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;