--- fs/ubifs/recovery.c

+++ fs/ubifs/recovery.c

@@ -299,6 +299,32 @@ int ubifs_recover_master_node(struct ubi

goto out_free;

}

memcpy(c->rcvrd_mst_node, c->mst_node, UBIFS_MST_NODE_SZ);

+

+ /*

+ * We had to recover the master node, which means there was an

+ * unclean reboot. However, it is possible that the master node

+ * is clean at this point, i.e., %UBIFS_MST_DIRTY is not set.

+ * E.g., consider the following chain of events:

+ *

+ * 1. UBIFS was cleanly unmounted, so the master node is clean

+ * 2. UBIFS is being mounted R/W and starts changing the master

+ * node in the first (%UBIFS_MST_LNUM). A power cut happens,

+ * so this LEB ends up with some amount of garbage at the

+ * end.

+ * 3. UBIFS is being mounted R/O. We reach this place and

+ * recover the master node from the second LEB

+ * (%UBIFS_MST_LNUM + 1). But we cannot update the media

+ * because we are being mounted R/O. We have to defer the

+ * operation.

+ * 4. However, this master node (@c->mst_node) is marked as

+ * clean (since the step 1). And if we just return, the

+ * mount code will be confused and won't recover the master

+ * node when it is re-mounter R/W later.

+ *

+ * Thus, to force the recovery by marking the master node as

+ * dirty.

+ */

+ c->mst_node->flags |= cpu_to_le32(UBIFS_MST_DIRTY);

} else {

/* Write the recovered master node */

c->max_sqnum = le64_to_cpu(mst->ch.sqnum) - 1;