Hi,

rsync -H and cpio's hardlink detection can be badly confused.  They will
think distinct files with the same inode number are hardlinks.  This could
be bad if you were making backups (though if you're making backups over
NFS, you are probably doing something that could be done better in a
different way).

'rysnc -x ' and 'find -mount/-xdev' will fail to work in
snapper config?
snapper is a very important user case.

Although  yet not some option like '-mount/-xdev' for '/bin/cp',
but maybe come soon.

I though the first patchset( crossmnt in nfs client) is the right way,
because in most case, subvol is a filesystem, not  a directory.

Best Regards
Wang Yugui (wangyugui@e16-tech.com)
2021/08/23