ext4: adjust the layout of the ext4_inode_info structure to save memory

Using pahole, we can see that there are some padding holes
in the current ext4_inode_info structure. Adjusting the
layout of ext4_inode_info can reduce these holes,
resulting in the size of the structure decreasing
from 2424 bytes to 2408 bytes.

Signed-off-by: Junchao Sun <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>

Author: jc2870

fs/ext4/ext4.h

@@ -1058,6 +1058,7 @@ struct ext4_inode_info {
 
 	/* Number of ongoing updates on this inode */
 	atomic_t  i_fc_updates;
+	atomic_t i_unwritten; /* Nr. of inflight conversions pending */
 
 	/* Fast commit wait queue for this inode */
 	wait_queue_head_t i_fc_wait;
@@ -1106,6 +1107,10 @@ struct ext4_inode_info {
 
 	/* mballoc */
 	atomic_t i_prealloc_active;
+
+	/* allocation reservation info for delalloc */
+	/* In case of bigalloc, this refer to clusters rather than blocks */
+	unsigned int i_reserved_data_blocks;
 	struct rb_root i_prealloc_node;
 	rwlock_t i_prealloc_lock;
 
@@ -1122,10 +1127,6 @@ struct ext4_inode_info {
 	/* ialloc */
 	ext4_group_t	i_last_alloc_group;
 
-	/* allocation reservation info for delalloc */
-	/* In case of bigalloc, this refer to clusters rather than blocks */
-	unsigned int i_reserved_data_blocks;
-
 	/* pending cluster reservations for bigalloc file systems */
 	struct ext4_pending_tree i_pending_tree;
 
@@ -1149,7 +1150,6 @@ struct ext4_inode_info {
 	 */
 	struct list_head i_rsv_conversion_list;
 	struct work_struct i_rsv_conversion_work;
-	atomic_t i_unwritten; /* Nr. of inflight conversions pending */
 
 	spinlock_t i_block_reservation_lock;