diff options
| -rw-r--r-- | fs/ubifs/recovery.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/fs/ubifs/recovery.c b/fs/ubifs/recovery.c index f94ddf7efba..31d09d16c28 100644 --- a/fs/ubifs/recovery.c +++ b/fs/ubifs/recovery.c @@ -299,6 +299,32 @@ int ubifs_recover_master_node(struct ubifs_info *c) 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; |