zfs-create(8): ZFS for swap: caution, clarity

[makhomed]

zfs-create(8): ZFS for swap: caution, clarity

Make the section heading more generic (the section relates to ZFS files as well as ZFS volumes).

Swapping to a ZFS volume is prone to deadlock. Remove the related instruction, direct readers to OpenZFS FAQ. Related, but not linked from within the manual page:

https://openzfs.github.io/openzfs-docs/Project%20and%20Community/FAQ.html#using-a-zvol-for-a-swap-device-on-linux (Using a zvol for a swap device on Linux).

Motivation and Context

Fixes issue #16891

Description

Backport patch from 6c29422 to branch 2.1-release

How Has This Been Tested?

man page updated only, no code changes.

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.

[gmelikov]

@makhomed such backports should be at least as git cherry-pick with all info about original authors (see that full commit message is here with original authors https://github.com/openzfs/zfs/pull/16781/commits ) , and let's add info about 2.1 release into PR title. And "Merge pull request" is not needed here too, you may drop it.