zpool: allow relative vdev paths

[tonyhutter]

Motivation and Context

Allow relative paths in zpool create.

Description

zpool create won't let you use relative paths to disks. This is annoying when you want to do:

zpool create tank ./diskfile

But have to do..

zpool create tank `pwd`/diskfile

This fixes it.

How Has This Been Tested?

Manually tested

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[amotin]

I worry about safety of this, considering we allow device name specification without the /dev/ prefix. It might create uncertainty. ./file1 might be specific, assuming caller expect this and knows what is his current directory, but some file1 might not.

[tonyhutter]

I worry about safety of this, considering we allow device name specification without the /dev/ prefix.

Good point, you could run into trouble if you had a file in your local directory with the same name as a /dev name (like a file called "sda"). How about we require a directory prefix if you're using a local file? Like zpool create tank ./file or zpool create tank ../file would be ok, but zpool create tank file would not?

[tonyhutter]

Ok, my latest push requires the filename to have a / in it.

[amotin]

I don't think just / is a sufficient guard, since we often have devices with / in the names, separating type of ID from some ID. I'd specifically check for ./ and ../, or may be some other projects already addressed similar issues and got deeper thoughts.