GFS2: Fix ail list traversal

In the recent patches to update the AIL list code, I managed to
forget that the ail list lock got dropped, even though I
added a comment specifically to remind myself :(

Reported-by: Barry Marson <bmarson@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index ad1f1887633f..cec26c00b50d 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -89,9 +89,9 @@ void gfs2_remove_from_ail(struct gfs2_bufdata *bd)
  *
  */
 
-static void gfs2_ail1_start_one(struct gfs2_sbd *sdp,
-                                struct writeback_control *wbc,
-                                struct gfs2_ail *ai)
+static int gfs2_ail1_start_one(struct gfs2_sbd *sdp,
+                               struct writeback_control *wbc,
+                               struct gfs2_ail *ai)
 __releases(&sdp->sd_ail_lock)
 __acquires(&sdp->sd_ail_lock)
 {
@@ -100,7 +100,6 @@ __acquires(&sdp->sd_ail_lock)
         struct gfs2_bufdata *bd, *s;
         struct buffer_head *bh;
 
-restart:
         list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list, bd_ail_st_list) {
                 bh = bd->bd_bh;
 
@@ -120,13 +119,17 @@ restart:
                 gl = bd->bd_gl;
                 list_move(&bd->bd_ail_st_list, &ai->ai_ail1_list);
                 mapping = bh->b_page->mapping;
+                if (!mapping)
+                        continue;
                 spin_unlock(&sdp->sd_ail_lock);
                 generic_writepages(mapping, wbc);
                 spin_lock(&sdp->sd_ail_lock);
                 if (wbc->nr_to_write <= 0)
                         break;
-                goto restart;
+                return 1;
         }
+
+        return 0;
 }
 
 
@@ -146,10 +149,12 @@ void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc)
 
         trace_gfs2_ail_flush(sdp, wbc, 1);
         spin_lock(&sdp->sd_ail_lock);
+restart:
         list_for_each_entry_reverse(ai, head, ai_list) {
                 if (wbc->nr_to_write <= 0)
                         break;
-                gfs2_ail1_start_one(sdp, wbc, ai); /* This may drop ail lock */
+                if (gfs2_ail1_start_one(sdp, wbc, ai))
+                        goto restart;
         }
         spin_unlock(&sdp->sd_ail_lock);
         trace_gfs2_ail_flush(sdp, wbc, 0);