[GFS2] Use list_for_each_entry_safe_reverse in gfs2_ail1_start()

This is an attempt to fix Red Hat bz 204364. I don't hit it all
the time, but with these changes, running postmark which used to
trigger it on a regular basis no longer appears to. So I'm not
saying that its 100% certain that its fixed, but it does look
promising at the moment.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 08b80b2..6112d64 100644 (file)
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -62,8 +62,9 @@ void gfs2_ail1_start(struct gfs2_sbd *sdp, int flags)
 {
        struct list_head *head = &sdp->sd_ail1_list;
        u64 sync_gen;
-       struct list_head *first, *tmp;
-       struct gfs2_ail *first_ai, *ai;
+       struct list_head *first;
+       struct gfs2_ail *first_ai, *ai, *tmp;
+       int done = 0;
 
        gfs2_log_lock(sdp);
        if (list_empty(head)) {
@@ -75,27 +76,25 @@ void gfs2_ail1_start(struct gfs2_sbd *sdp, int flags)
        first = head->prev;
        first_ai = list_entry(first, struct gfs2_ail, ai_list);
        first_ai->ai_sync_gen = sync_gen;
-       gfs2_ail1_start_one(sdp, first_ai);
+       gfs2_ail1_start_one(sdp, first_ai); /* This may drop log lock */
 
        if (flags & DIO_ALL)
                first = NULL;
 
-       for (;;) {
+       while(!done) {
                if (first && (head->prev != first ||
                              gfs2_ail1_empty_one(sdp, first_ai, 0)))
                        break;
 
-               for (tmp = head->prev; tmp != head; tmp = tmp->prev) {
-                       ai = list_entry(tmp, struct gfs2_ail, ai_list);
+               done = 1;
+               list_for_each_entry_safe_reverse(ai, tmp, head, ai_list) {
                        if (ai->ai_sync_gen >= sync_gen)
                                continue;
                        ai->ai_sync_gen = sync_gen;
-                       gfs2_ail1_start_one(sdp, ai);
+                       gfs2_ail1_start_one(sdp, ai); /* This may drop log lock */
+                       done = 0;
                        break;
                }
-
-               if (tmp == head)
-                       break;
        }
 
        gfs2_log_unlock(sdp);