kern/60082: swap encryption corrupt data

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>Number:         60082
>Category:       kern
>Synopsis:       swap encryption corrupt data
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Mar 15 03:35:00 +0000 2026
>Originator:     YAMAMOTO Takashi
>Release:        -current
>Organization:
>Environment:
amd64
>Description:
when paging out, uvm_swap_io encrypts the page contents
and then issues write requests to swapdev. if the write fails
for some reason, the pageout will be cancelled. but it leaves
the data in the pages encrypted.
note: we are in the pagedaemon context and some kind of errors
are "common".  eg. VOP_BMAP has special cases for the pagedaemon
to return ENOMEM.

>How-To-Repeat:
use swap.
>Fix: