[Cluster-devel] [GFS2 PATCH] gfs2: fix trans slab error when withdraw occurs inside log_flush

[Bob Peterson <rpeterso@redhat.com>]

----- Original Message -----
> I'm not sure quite what the aim is here... are you sure that it is ok to
> move something to the AIL list if there has been a withdrawal? If the
> log flush has not completed correctly then we should not be moving
> anything to the AIL lists I think,
> 
> Steve.

Yes, I'm sure it's okay in this case. We only add it temporarily to the
ail1 list so that function ail_drain() finds and removes it like the rest.

I only coded it this way because Andreas didn't like my somewhat longer
previous implementation, which follows.

Regards,

Bob

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 3e4734431783..0c45851b88d5 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -845,8 +845,15 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
 /**
  * ail_drain - drain the ail lists after a withdraw
  * @sdp: Pointer to GFS2 superblock
+ * @flush_tr: If non-null, transaction that was being flushed
+ *
+ * We're draining the ail lists after a withdraw, during a log flush op.
+ * If the log flush was targeting a specific transaction, it will never
+ * go through "after" lops processing, so we need to free it here.
+ * If we find it on one of the ail lists, we free it as we dequeue it.
+ * If we don't find it, we free it at the end.
  */
-static void ail_drain(struct gfs2_sbd *sdp)
+static void ail_drain(struct gfs2_sbd *sdp, struct gfs2_trans *flush_tr)
 {
 	struct gfs2_trans *tr;
 
@@ -865,6 +872,8 @@ static void ail_drain(struct gfs2_sbd *sdp)
 		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
 		list_del(&tr->tr_list);
 		gfs2_trans_free(sdp, tr);
+		if (tr == flush_tr)
+			flush_tr = NULL;
 	}
 	while (!list_empty(&sdp->sd_ail2_list)) {
 		tr = list_first_entry(&sdp->sd_ail2_list, struct gfs2_trans,
@@ -872,7 +881,11 @@ static void ail_drain(struct gfs2_sbd *sdp)
 		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
 		list_del(&tr->tr_list);
 		gfs2_trans_free(sdp, tr);
+		if (tr == flush_tr)
+			flush_tr = NULL;
 	}
+	if (flush_tr)
+		gfs2_trans_free(sdp, flush_tr);
 	spin_unlock(&sdp->sd_ail_lock);
 }
 
@@ -1002,7 +1015,7 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 
 out:
 	if (gfs2_withdrawn(sdp)) {
-		ail_drain(sdp); /* frees all transactions */
+		ail_drain(sdp, tr); /* frees all transactions */
 		tr = NULL;
 	}