ext4: fix possible leak of s_journal_flag_rwsem in error path

Fixes: c8585c6fcaf2 ("ext4: fix races between changing inode journal ...")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 4.7

fs/ext4/super.c

@@ -4510,6 +4510,7 @@ failed_mount6:
 	percpu_counter_destroy(&sbi->s_freeinodes_counter);
 	percpu_counter_destroy(&sbi->s_dirs_counter);
 	percpu_counter_destroy(&sbi->s_dirtyclusters_counter);
+	percpu_free_rwsem(&sbi->s_journal_flag_rwsem);
 failed_mount5:
 	ext4_ext_release(sb);
 	ext4_release_system_zone(sb);