@@ -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.
+ */
Guys, I have an embedded product running a system based on linux-2.6.29, originally from the IC supplier, but patched and modified to our spec. Recently we have had two units go down with the same UBI-FS Master Node failure, both in LEB-2 at slightly different offsets. The console log looks like this:- [ 6.645845] UBIFS error (pid 1): ubifs_scan: corrupt empty space at LEB 2:86016 [ 6.653268] UBIFS error (pid 1): ubifs_scanned_corruption: corrupted data at LEB 2:86016 [ 6.668163] UBIFS error (pid 1): ubifs_scan: LEB 2 scanning failed [ 6.889661] UBIFS error (pid 1): ubifs_recover_master_node: failed to recover master node [ 6.898497] List of all partitions: [ 6.902188] 1f00 128 mtdblock0 (driver?) [ 6.907218] 1f01 768 mtdblock1 (driver?) [ 6.912314] 1f02 128 mtdblock2 (driver?) [ 6.917318] 1f03 4096 mtdblock3 (driver?) [ 6.922395] 1f04 4096 mtdblock4 (driver?) [ 6.927397] 1f05 65536 mtdblock5 (driver?) [ 6.932464] 1f06 184320 mtdblock6 (driver?) [ 6.937455] No filesystem could mount root, tried: ubifs [ 6.942988] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) I found two patches to fs/ubifs/recovery.c since 2.6.29 which I applied, but they did not fix the corrupted flash. These two patches were this one:- + 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;