ZTS: testing for leaked key mappings in encrypted non-raw send

[gamanakis]

Motivation and Context

See issue #12014.

Description

This test covers a bug fixed by commit ea74cde: performing an incremental non-raw send from an encrypted filesystem followed by exporting the pool. Before that commit, exporting the sending pool in this scenario would trigger a panic.

VERIFY(avl_is_empty(&sk->sk_dsl_keys)) failed
PANIC at dsl_crypt.c:353:spa_keystore_fini()
Call Trace:
spl_dumpstack+0x29/0x2f [spl]
spl_panic+0xd1/0xe9 [spl]
spl_assert.constprop.0+0x1a/0x30 [zfs]
spa_keystore_fini+0xc2/0xf0 [zfs]
spa_deactivate+0x25f/0x610 [zfs]
spa_evict_all+0xf4/0x200 [zfs]
spa_fini+0x13/0x140 [zfs]
zfs_kmod_fini+0x72/0xc0 [zfs]
openzfs_fini_os+0x13/0x3a [zfs]
openzfs_fini+0x9/0x6b8 [zfs]

How Has This Been 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)
• Quality assurance (non-breaking change which makes the code more robust against bugs)
• 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.

[behlendorf]

Thanks for following up with a test case for this leak.

[gamanakis]

@behlendorf I noticed the FreeBSDs were failing, due to dsync in dd.
306399e: removed dsync in dd.

[amotin]

I think this would be cleaner:

[gamanakis]

523ed28: echo converted to log_note