+ /*
+ * We've probably journalled the indirect block several
+ * times during the truncate. But it's no longer
+ * needed and we now drop it from the transaction via
+ * journal_revoke().
+ *
+ * That's easy if it's exclusively part of this
+ * transaction. But if it's part of the committing
+ * transaction then journal_forget() will simply
+ * brelse() it. That means that if the underlying
+ * block is reallocated in ext3_get_block(),
+ * unmap_underlying_metadata() will find this block
+ * and will try to get rid of it. damn, damn. Thus
+ * we don't allow a block to be reallocated until
+ * a transaction freeing it has fully committed.
+ *
+ * We also have to make sure journal replay after a
+ * crash does not overwrite non-journaled data blocks
+ * with old metadata when the block got reallocated for
+ * data. Thus we have to store a revoke record for a
+ * block in the same transaction in which we free the
+ * block.
+ */
+ ext3_forget(handle, 1, inode, bh, bh->b_blocknr);
+