[LogFS] Prevent memory corruption on large deletes

Removing sufficiently large files would create aliases for a large
number of segments.  This in turn results in a large number of journal
entries and an overflow of s_je_array.

Cheap fix is to add a BUG_ON, turning memory corruption into something
annoying, but less dangerous.  Real fix is to count the number of
affected segments and prevent the problem completely.

Signed-off-by: Joern Engel <joern@logfs.org>

fs/logfs/super.c

@@ -451,6 +451,8 @@ static int logfs_read_sb(struct super_block *sb, int read_only)
 
 	btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool);
 	btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool);
+	btree_init_mempool32(&super->s_shadow_tree.segment_map,
+			super->s_btree_pool);
 
 	ret = logfs_init_mapping(sb);
 	if (ret)