creating a dm-linear.ko in a current kernel.

creating a dm-linear.ko in a current kernel.

[John Utz]

Hello;

I have a linear device that i am attempting to harness to device mapper.

My expectation that i developed based on my reading was that I could start from a dm-linear.c => dm-linear.ko and go from there.

But dm-linear.c gets linked into dm-mod.ko, not dm-linear.ko.

Has dm-linear always been part of dm-mod? i see some stuff on the net that implies the existence of dm-linear.ko, but i have poked around in menuconfig and i can find no specific entry to create it.

Any suggestions as to how to proceed would be greatly appreciated.

tnx!

johnu

Re: creating a dm-linear.ko in a current kernel.

[John Utz]

Solved my own issue methinks, the name of the module that i am finding in drivers/md/ is linear.ko, not dm-linear.ko. that was unexpected. i note further that there are other non 'dm- decorated' lkms in md as well, such as multipath, faulty, raid0, etc.

is there an implication associated with things decorated with dm- vs things not decorated with dm- in the md directory?

tnx!

johnu
________________________________________
From: dm-devel-bounces@redhat.com [dm-devel-bounces@redhat.com] on behalf of John Utz [John.Utz@wdc.com]
Sent: Monday, February 24, 2014 2:01 PM
To: dm-devel@redhat.com
Subject: [dm-devel] creating a dm-linear.ko in a current kernel.

Hello;

I have a linear device that i am attempting to harness to device mapper.

My expectation that i developed based on my reading was that I could start from a dm-linear.c => dm-linear.ko and go from there.

But dm-linear.c gets linked into dm-mod.ko, not dm-linear.ko.

Has dm-linear always been part of dm-mod? i see some stuff on the net that implies the existence of dm-linear.ko, but i have poked around in menuconfig and i can find no specific entry to create it.

Any suggestions as to how to proceed would be greatly appreciated.

tnx!

johnu

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Re: creating a dm-linear.ko in a current kernel.

[Bryn M. Reeves]

On 02/24/2014 10:44 PM, John Utz wrote:
> Solved my own issue methinks, the name of the module that i am
> finding in drivers/md/ is linear.ko, not dm-linear.ko. that was

That's the MD linear personality not the device-mapper linear target. It
allows you to build JBOD (concatentation) arrays using the MD RAID
subsystem.

> unexpected. i note further that there are other non 'dm- decorated'
> lkms in md as well, such as multipath, faulty, raid0, etc.

These are also MD personalities.

> is there an implication associated with things decorated with dm- vs
> things not decorated with dm- in the md directory?

The device-mapper targets all have a dm-* prefix (there are other files
in drivers/md with names beginning with 'dm', e.g. dm.c, dm-table.c but
those are part of the device-mapper core).

The dm-linear target is always built into the core dm-mod - see the
Makefile rules in drivers/md/Makefile for details. The device-mapper
bits are right at the top.

Regards,
Bryn.

Re: creating a dm-linear.ko in a current kernel.

[John Utz]

Good Morning Bryn;

Thankyou!
________________________________________
From: Bryn M. Reeves [bmr@redhat.com]
Sent: Tuesday, February 25, 2014 2:53 AM
To: device-mapper development
Cc: John Utz
Subject: Re: [dm-devel] creating a dm-linear.ko in a current kernel.

On 02/24/2014 10:44 PM, John Utz wrote:
> Solved my own issue methinks, the name of the module that i am
> finding in drivers/md/ is linear.ko, not dm-linear.ko. that was

That's the MD linear personality not the device-mapper linear target. It
allows you to build JBOD (concatentation) arrays using the MD RAID
subsystem.

Could you briefly explain the concept of 'personality' in this context? I see it referred to but i have yet to find an explanation thereof. perhaps i have been looking in the wrong place.

I am also motivated by your response to see if i am barking up the wrong tree. :-)

I have a need to harness a hard drive like thing that can only be written to in linear fashion using device mapper.

I had assumed that i needed to start from the existing linear implementation that is in dm-linear.

Am I wrong and everything i need is already coded and i just need to create an appropriate configuration file of some kind?

Please advise when you get a chance.

Thankyou in advance.

johnu

<SNIP>

Regards,
Bryn.

Re: creating a dm-linear.ko in a current kernel.

[johnstra10]

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Hey John... it's Jihn Strange... funny meeting you here on dm-devel. So your playing around with dm, huh?  I did a few months ago. I like the architecture, as you're seeing, the implementation lacks dicipline.  Hope things are going well for you guys at RSC.
-john




Sent from Samsung tablet

-------- Original message --------
From: John Utz <John.Utz@wdc.com> 
Date: 02/24/2014  3:44 PM  (GMT-07:00) 
To: device-mapper development <dm-devel@redhat.com> 
Subject: Re: [dm-devel] creating a dm-linear.ko in a current kernel. 
 
Solved my own issue methinks, the name of the module that i am finding in drivers/md/ is linear.ko, not dm-linear.ko. that was unexpected. i note further that there are other non 'dm- decorated' lkms in md as well, such as multipath, faulty, raid0, etc.

is there an implication associated with things decorated with dm- vs things not decorated with dm- in the md directory?

tnx!

johnu
________________________________________
From: dm-devel-bounces@redhat.com [dm-devel-bounces@redhat.com] on behalf of John Utz [John.Utz@wdc.com]
Sent: Monday, February 24, 2014 2:01 PM
To: dm-devel@redhat.com
Subject: [dm-devel] creating a dm-linear.ko in a current kernel.

Hello;

I have a linear device that i am attempting to harness to device mapper.

My expectation that i developed based on my reading was that I could start from a dm-linear.c => dm-linear.ko and go from there.

But dm-linear.c gets linked into dm-mod.ko, not dm-linear.ko.

Has dm-linear always been part of dm-mod? i see some stuff on the net that implies the existence of dm-linear.ko, but i have poked around in menuconfig and i can find no specific entry to create it.

Any suggestions as to how to proceed would be greatly appreciated.

tnx!

johnu

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