UBIFS: fix-up free space earlier

The free space fixup is currently initiated during mount after the call to
ubifs_write_master() which results in a write to PEBs; this has been observed
with the patch 'assert no fixup when writing a node' applied:

Move the free space fixup on mount to before the calls to
ubifs_recover_inl_heads() and ubifs_write_master(). This results in no
assertions with the previously mentioned patch applied.

Artem: tweaked the patch a bit

Signed-off-by: Ben Gardiner <bengardiner@nanometrics>
Reviewed-by: Matthew L. Creech <mlcreech@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/super.c

@@ -1282,13 +1282,13 @@ static int mount_ubifs(struct ubifs_info *c)
 	if (err)
 		goto out_master;
 
+	init_constants_master(c);
+
 	if ((c->mst_node->flags & cpu_to_le32(UBIFS_MST_DIRTY)) != 0) {
 		ubifs_msg("recovery needed");
 		c->need_recovery = 1;
 	}
 
-	init_constants_master(c);
-
 	if (c->need_recovery && !c->ro_mount) {
 		err = ubifs_recover_inl_heads(c, c->sbuf);
 		if (err)
@@ -1299,6 +1299,12 @@ static int mount_ubifs(struct ubifs_info *c)
 	if (err)
 		goto out_master;
 
+	if (!c->ro_mount && c->space_fixup) {
+		err = ubifs_fixup_free_space(c);
+		if (err)
+			goto out_master;
+	}
+
 	if (!c->ro_mount) {
 		/*
 		 * Set the "dirty" flag so that if we reboot uncleanly we
@@ -1402,12 +1408,6 @@ static int mount_ubifs(struct ubifs_info *c)
 	} else
 		ubifs_assert(c->lst.taken_empty_lebs > 0);
 
-	if (!c->ro_mount && c->space_fixup) {
-		err = ubifs_fixup_free_space(c);
-		if (err)
-			goto out_infos;
-	}
-
 	err = dbg_check_filesystem(c);
 	if (err)
 		goto out_infos;