[GFS2] Fix list corruption in lops.c

The patch below appears to fix the list corruption that we are seeing on
occasion. Although the transaction structure is private to a single
thread, when the queued structures are dismantled during an in-core
commit, its possible for a different thread to be trying to add the same
structure to another, new, transaction at the same time.

To avoid this, this patch takes the log spinlock during this operation.

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

fs/gfs2/lops.c

@@ -69,13 +69,16 @@ static void buf_lo_add(struct gfs2_sbd *sdp, struct gfs2_log_element *le)
 	struct gfs2_bufdata *bd = container_of(le, struct gfs2_bufdata, bd_le);
 	struct gfs2_trans *tr;
 
-	if (!list_empty(&bd->bd_list_tr))
+	gfs2_log_lock(sdp);
+	if (!list_empty(&bd->bd_list_tr)) {
+		gfs2_log_unlock(sdp);
 		return;
-
+	}
 	tr = current->journal_info;
 	tr->tr_touched = 1;
 	tr->tr_num_buf++;
 	list_add(&bd->bd_list_tr, &tr->tr_list_buf);
+	gfs2_log_unlock(sdp);
 
 	if (!list_empty(&le->le_list))
 		return;
@@ -84,7 +87,6 @@ static void buf_lo_add(struct gfs2_sbd *sdp, struct gfs2_log_element *le)
 
 	gfs2_meta_check(sdp, bd->bd_bh);
 	gfs2_pin(sdp, bd->bd_bh);
-
 	gfs2_log_lock(sdp);
 	sdp->sd_log_num_buf++;
 	list_add(&le->le_list, &sdp->sd_log_le_buf);
@@ -98,11 +100,13 @@ static void buf_lo_incore_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 	struct list_head *head = &tr->tr_list_buf;
 	struct gfs2_bufdata *bd;
 
+	gfs2_log_lock(sdp);
 	while (!list_empty(head)) {
 		bd = list_entry(head->next, struct gfs2_bufdata, bd_list_tr);
 		list_del_init(&bd->bd_list_tr);
 		tr->tr_num_buf--;
 	}
+	gfs2_log_unlock(sdp);
 	gfs2_assert_warn(sdp, !tr->tr_num_buf);
 }
 
@@ -462,13 +466,17 @@ static void databuf_lo_add(struct gfs2_sbd *sdp, struct gfs2_log_element *le)
 	struct address_space *mapping = bd->bd_bh->b_page->mapping;
 	struct gfs2_inode *ip = GFS2_I(mapping->host);
 
+	gfs2_log_lock(sdp);
 	tr->tr_touched = 1;
 	if (list_empty(&bd->bd_list_tr) &&
 	    (ip->i_di.di_flags & GFS2_DIF_JDATA)) {
 		tr->tr_num_buf++;
 		list_add(&bd->bd_list_tr, &tr->tr_list_buf);
+		gfs2_log_unlock(sdp);
 		gfs2_pin(sdp, bd->bd_bh);
 		tr->tr_num_buf_new++;
+	} else {
+		gfs2_log_unlock(sdp);
 	}
 	gfs2_trans_add_gl(bd->bd_gl);
 	gfs2_log_lock(sdp);