ext4: mitigatin cacheline false sharing in struct ext4_inode_info

hulk inclusion
category: performance
bugzilla: https://gitee.com/openeuler/kernel/issues/I8J122



--------------------------------

In the test of execl, shell1 and shell8 of UnixBench, L3 false sharing
occurs between rwsem_try_write_lock_unqueued() and filemap_map_pages().

The offset between address_space.host and address_space.i_mmap_rwsem
is 48. It may occur L3 false sharing. Their offsets in struct ext4_inode_info
is 696 and 744, so when the address of ext4_inode_info after L3 aligned,
it may occur L3 false sharing in the following condition:

[0x00 ~ 0x10] false sharing
[0x18 ~ 0x40] no false sharing
[0x48 ~ 0x80] false sharing

Change the offset of 'vfs_inode' from 320 to 360 in ext4_inode_info and
make the address of ext4_inode_info L3 aligned, so the offset of host
and i_mmap_rwsem in ext4_inode_info is changed to 736 and 784, it can
make them in different L3 to avoid false sharing.

./Run -c 96 -i 3 execl

Before this patch:
System Benchmarks Partial Index              BASELINE       RESULT    INDEX
Execl Throughput                                 43.0      24238.0   5636.8
                                                                   ========
System Benchmarks Index Score (Partial Only)                         5636.8

After this patch:
System Benchmarks Partial Index              BASELINE       RESULT    INDEX
Execl Throughput                                 43.0      29363.7   6828.8
                                                                   ========
System Benchmarks Index Score (Partial Only)                         6828.8

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Zeng Heng <zengheng4@huawei.com>