Is metadata (dates) for hardlinked files shared or unique? Inodes and linked files!

Question

I always assumed that the dates in each inode were maintained separately even with hardlinks.

However if I change (touch/slap) the date of a hardlink file all other hardlinks to the same file show the same date change!

$ ln test.sh testlink.sh
$ slap test.sh
crtime : 5e7d6a29 - Fri 2020-03-27 10:51:21
mtime  : 5e7d6a29 - Fri 2020-03-27 10:51:21
atime  : 5e815c32 - Mon 2020-03-30 10:40:50
ctime  : 5e815c31 - Mon 2020-03-30 10:40:49
$ slap testlink.sh
crtime : 5e7d6a29 - Fri 2020-03-27 10:51:21
mtime  : 5e7d6a29 - Fri 2020-03-27 10:51:21
atime  : 5e815c32 - Mon 2020-03-30 10:40:50
ctime  : 5e815c31 - Mon 2020-03-30 10:40:49
$ slap test.sh -C 2005-02-13T08:47:43+00:00
$ slap test.sh
crtime : 420ea3af - Sun 2005-02-13 08:47:43
mtime  : 5e7d6a29 - Fri 2020-03-27 10:51:21
atime  : 5e815c32 - Mon 2020-03-30 10:40:50
ctime  : 5e815c31 - Mon 2020-03-30 10:40:49
$ slap testlink.sh
crtime : 420ea3af - Sun 2005-02-13 08:47:43
mtime  : 5e7d6a29 - Fri 2020-03-27 10:51:21
atime  : 5e815c32 - Mon 2020-03-30 10:40:50
ctime  : 5e815c31 - Mon 2020-03-30 10:40:49

(slap is a utility I wrote to change file date metadata in the inode including crtime.)

Can anyone who has a better understanding of the EXT2/3/4 file system care to comment.

So where is the filename stored if the inode is not unique? Is there a higher level structure that contains the filename that points to the inode in which the dates are stored?

Answer 1

Hardlink provides one or more alternate paths for an inode. As per man 2 link, there is no difference between the original and newly linked paths.

As they share the same inode, all the metadata are shared among them.