ext4: Convert to generic reserved quota's space management.

This patch also fixes write vs chown race condition.

Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 827bde1..6ed9aa9 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -704,6 +704,9 @@
 	ei->i_allocated_meta_blocks = 0;
 	ei->i_delalloc_reserved_flag = 0;
 	spin_lock_init(&(ei->i_block_reservation_lock));
+#ifdef CONFIG_QUOTA
+	ei->i_reserved_quota = 0;
+#endif
 	INIT_LIST_HEAD(&ei->i_aio_dio_complete_list);
 	ei->cur_aio_dio = NULL;
 	ei->i_sync_tid = 0;
@@ -1014,7 +1017,9 @@
 	.reserve_space	= dquot_reserve_space,
 	.claim_space	= dquot_claim_space,
 	.release_rsv	= dquot_release_reserved_space,
+#ifdef CONFIG_QUOTA
 	.get_reserved_space = ext4_get_reserved_space,
+#endif
 	.alloc_inode	= dquot_alloc_inode,
 	.free_space	= dquot_free_space,
 	.free_inode	= dquot_free_inode,