kern/48065: swapctl -d path dangerous?

[kardel%netbsd.org@localhost]

>Number:         48065
>Category:       kern
>Synopsis:       swapctl -d path seems to cause data inconsistencies
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jul 19 07:35:00 +0000 2013
>Originator:     Frank Kardel
>Release:        NetBSD 6.99.20
>Organization:
        
>Environment:
        
        
System: NetBSD pip.kardel.name 6.99.20 NetBSD 6.99.20 (PIPGEN) #34: Sun May 26 
16:57:25 CEST 2013 ... amd64
Architecture: x86_64
Machine: amd64
>Description:
        While running vm-heavy postgresl load jobs (open streetmap planet load) 
the
        command swapctl -d /dev/<some swap device> often leads to a postgresql 
(9.2)
        abort due to an unexpected zero page block.
>How-To-Repeat:
        run an open streetmap planet load with swap on mechanical disks (being 
used for
        paging) add swap from an SSD device and delete swap from mechanical 
device causing
        massive page-in from the mechanical device. Watch postgresql abort over
2013-07-17T06:35:46.302452+02:00 pip.kardel.name postgres 7165 - - [6-1] ERROR: 
 index "planet_osm_roads_index" contains unexpected zero page at block 1844
2013-07-17T06:35:46.302638+02:00 pip.kardel.name postgres 7165 - - [6-2] HINT:  
Please REINDEX it.
2013-07-17T06:35:46.302667+02:00 pip.kardel.name postgres 7165 - - [6-3] 
CONTEXT:  COPY planet_osm_roads, line 1448077: "33138513       \N      \N      
\N      \N      \N      \N      \N      \N      \N      \N      \N      \N      
\N      \N      \N      \N      \N      \N      \N      \N      \N      \N      
\N      \N      \N      primary \N      \N      \N..."
2013-07-17T06:35:46.302696+02:00 pip.kardel.name postgres 7165 - - [6-4] 
STATEMENT:  COPY planet_osm_roads (osm_id,"access","ad....
        I have seen that twice. If the load runs without a swapctl -d the load 
succeeds.
>Fix:
        Don't use swapctl -d unless the swap space on that device is not used.

>Unformatted: