ext4: replace i_delalloc_reserved_flag with EXT4_STATE_DELALLOC_RESERVED

Remove the short element i_delalloc_reserved_flag from the
ext4_inode_info structure and replace it a new bit in i_state_flags.
Since we have an ext4_inode_info for every ext4 inode cached in the
inode cache, any savings we can produce here is a very good thing from
a memory utilization perspective.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 14c3af2..adf96b8 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -592,7 +592,8 @@
 	 * Account for the allocated meta blocks.  We will never
 	 * fail EDQUOT for metdata, but we do account for it.
 	 */
-	if (!(*errp) && EXT4_I(inode)->i_delalloc_reserved_flag) {
+	if (!(*errp) &&
+	    ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
 		spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
 		EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 		spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);