UBIFS: increment commit number earlier

Increment the commit number at the beginnig of the commit, instead
of doing this after the commit. This is needed for further
optimizations.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/fs/ubifs/commit.c b/fs/ubifs/commit.c
index 3b51631..0a6aa2c 100644
--- a/fs/ubifs/commit.c
+++ b/fs/ubifs/commit.c
@@ -74,6 +74,7 @@
 			goto out_up;
 	}
 
+	c->cmt_no += 1;
 	err = ubifs_gc_start_commit(c);
 	if (err)
 		goto out_up;
@@ -115,7 +116,7 @@
 		goto out;
 
 	mutex_lock(&c->mst_mutex);
-	c->mst_node->cmt_no      = cpu_to_le64(++c->cmt_no);
+	c->mst_node->cmt_no      = cpu_to_le64(c->cmt_no);
 	c->mst_node->log_lnum    = cpu_to_le32(new_ltail_lnum);
 	c->mst_node->root_lnum   = cpu_to_le32(zroot.lnum);
 	c->mst_node->root_offs   = cpu_to_le32(zroot.offs);