Re: cp: behavior regression in 8.23

[TAMUKI Shoichi]

Hello Padraig,

From: Padraig Brady <address@hidden>
Subject: Re: cp: behavior regression in 8.23
Date: Fri, 30 Jan 2015 12:46:16 +0000

> This change was made for performance reasons:
>   https://oss.oracle.com/~mason/acp/
>   http://home.ifi.uio.no/paalh/publications/files/ipccc09.pdf

Yes, I know.  In a particular case (depending on filesystems or using
way of directory structures,) using directory lists ordered by inode
can speed up.

> What's the particular problem you have with the order
> of the files in the tar archive, so I understand your issue completely?

The point is cp should keep the function to preserve the deterministic
directory structure of the original files/directories in the copy.
That was possible with the cp in coreutils-8.22 or earlier.

> I see that tar 1.28 has the --sort option.
> Perhaps if that supported --sort=mtime it would cater for your use case
> of reproducible tar archives with a specific order.

Ah, the case (January, February, ...) is just an example to explain
the issue.  It is a mere coincidence they are sorted in mtime order.

Here is the more practical example using cp in coreutils-8.23:

tamuki@wombat:~/work32$ ls -fl coreutils-8.22
total 8409088
drwxr-xr-x  6 tamuki users    4096 Jan 31 14:48 ./
drwxr-xr-x  3 tamuki users    4096 Jan 31 14:40 ../
-rwxr-xr-x  1 tamuki users    8753 Dec 24 15:07 PlamoBuild.coreutils-8.22*
-rw-------  1 tamuki users  186031 Jan 31 14:48 nohup.out
-rw-r--r--  1 tamuki users 5335124 Dec 14  2013 coreutils-8.22.tar.xz
drwxrwxr-x 12 tamuki users    4096 Dec 14  2013 coreutils-8.22/
drwxrwxr-x 12 tamuki users    4096 Jan 31 14:47 build/
drwxr-xr-x  6 root   root     4096 Jan 31 14:48 work/
drwxr-xr-x  2 root   root     4096 Jan 31 14:48 pivot/
-rw-r--r--  1 root   root        0 Jan 31 14:48 i.st
-rw-r--r--  1 root   root        0 Jan 31 14:48 i.et
-rw-r--r--  1 root   root  2843748 Jan 31 14:48 coreutils-8.22-i686-P2.txz
tamuki@wombat:~/work32$ sudo cp -a coreutils-8.22 coreutils-8.23
tamuki@wombat:~/work32$ ls -fl coreutils-8.23
total 8409088
drwxr-xr-x  6 tamuki users    4096 Jan 31 14:48 ./
drwxr-xr-x  4 tamuki users    4096 Jan 31 14:50 ../
-rw-------  1 tamuki users  186031 Jan 31 14:48 nohup.out
-rw-r--r--  1 tamuki users 5335124 Dec 14  2013 coreutils-8.22.tar.xz
drwxrwxr-x 12 tamuki users    4096 Dec 14  2013 coreutils-8.22/
drwxrwxr-x 12 tamuki users    4096 Jan 31 14:47 build/
-rw-r--r--  1 root   root        0 Jan 31 14:48 i.st
-rw-r--r--  1 root   root        0 Jan 31 14:48 i.et
-rwxr-xr-x  1 tamuki users    8753 Dec 24 15:07 PlamoBuild.coreutils-8.22*
-rw-r--r--  1 root   root  2843748 Jan 31 14:48 coreutils-8.22-i686-P2.txz
drwxr-xr-x  6 root   root     4096 Jan 31 14:48 work/
drwxr-xr-x  2 root   root     4096 Jan 31 14:48 pivot/

Anyway, in some cases, the copying directory tree will need to be done
as fast as possible, even ignoring the order of the readdir calls.
However, I don't think changing the specification will be a good idea
because cp has been used in the same manner as before for close to
three decades.

So, I propose to add --sort={none,name,inode} option to cp command.

Regards,
TAMUKI Shoichi