kern/148540: [geom] geom_sched breaks ata devices

[Marcin Wisnicki]

The following reply was made to PR kern/148540; it has been noted by GNATS.

From: Marcin Wisnicki <mwisnicki+freebsd at gmail.com>
To: "Andrey V. Elsukov" <bu7cher at yandex.ru>
Cc: bug-followup at freebsd.org, "Anton A. Barsukov" <iscsi at zesdid.com>, 
	Luigi Rizzo <luigi at freebsd.org>
Subject: Re: kern/148540: [geom] geom_sched breaks ata devices
Date: Thu, 15 Jul 2010 16:06:01 +0200

 On Wed, Jul 14, 2010 at 16:32, Marcin Wisnicki
 <mwisnicki+freebsd at gmail.com> wrote:
 > 2010/7/14 Andrey V. Elsukov <bu7cher at yandex.ru>:
 >> Hi,
 >>
 >> can you test attached patch?
 >>
 >
 > Forwarding ioctls works but I'm thinking that maybe gsched should
 > insert itself as a sibling to DEV and reattach all non-DEV consumers
 > (though that would mean you could bypass scheduler by directly opening
 > device).
 > Something like this:
 > http://wisnia21.freeshell.org/f/freebsd/geom_sched-insertion.png
 >
 
 One more thing. Currently gsched messes up names of disk geoms;
 
 # geom disk status
       Name  Status  Components
 ad0.sched.     N/A  N/A
        ad1     N/A  N/A
        cd0     N/A  N/A
        da0     N/A  N/A
        da1     N/A  N/A
 
 # sysctl -b kern.geom.conftxt | grep -a DISK
 0 DISK da1 4060086272 512 hd 255 sc 63
 0 DISK da0 1000204886016 512 hd 255 sc 63
 0 DISK cd0 0 2048 hd 0 sc 0
 0 DISK ad1 120034123776 512 hd 16 sc 255
 0 DISK ad0.sched. 41109061120 512 hd 16 sc 255
 
 Besides not looking good it breaks tools that use this information
 (like causing sade and sysinstall to segfault).
 
 Or maybe it is a bug of geom(8)-status and kern.geom.conftxt ?
 It seems like they print name of geom provider instead of the name of geom.
 
 ghost# geom disk status ad0
       Name  Status  Components
 ad0.sched.     N/A  N/A
 ghost# geom disk status ad0.sched.
 geom: No such geom: ad0.sched..
 ghost# geom disk list ad0.sched.
 geom: No such geom: ad0.sched..
 ghost# geom disk list ad0
 Geom name: ad0
 Providers:
 1. Name: ad0.sched.
    Mediasize: 41109061120 (38G)
    Sectorsize: 512
    Mode: r7w7e21
    fwsectors: 255
    fwheads: 16