bio aio: Destroy ephemeral mapping before unwiring page.

[kib]

Summary

Apparently some architectures, like ppc in its hashed page tables variants, account mappings by pmap_qenter() in the response from pmap_is_page_mapped().

Reported by: alc

[alc]

sys/kern/vfs_aio.c

2348–2349 ↗

(On Diff #80101)

These two assignments are only relevant if job->pbuf != NULL. So, they could move inside the "if" statement, just before the AIO_LOCK(ki). (In fact, I would just eliminate the variable userp.)

[kib]

Eliminate userp.