What can be used instead of /dev/disk/by-path/* symlinks?

What can be used instead of /dev/disk/by-path/* symlinks?

[Dorau, Lukasz]

Hi Neil,

The /dev/disk/by-path/* symlinks are not created for ATA devices in systems using systemd v182+, so mdadm cannot use them in case of policies and udev rules (mdadm -If --path=...)

What do you think - what should be used instead? The symlinks from /sys/block/* ?

Regards,
Lukasz

Re: What can be used instead of /dev/disk/by-path/* symlinks?

[NeilBrown]

[-- Attachment #1: Type: text/plain, Size: 959 bytes --]

On Tue, 17 Dec 2013 09:10:44 +0000 "Dorau, Lukasz" <lukasz.dorau@intel.com>
wrote:

> Hi Neil,

I'd really rather people addressed thing to the list, not just to me.  There
are many competent and interested people here other than me, and you
should expect them to have an opinion and ask for it.

Personally, I really don't care.  Does anyone know what udev changed?  Maybe
we should ask udev developers to change it back.

NeilBrown

> 
> The /dev/disk/by-path/* symlinks are not created for ATA devices in systems using systemd v182+, so mdadm cannot use them in case of policies and udev rules (mdadm -If --path=...)
> 
> What do you think - what should be used instead? The symlinks from /sys/block/* ?
> 
> Regards,
> Lukasz
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 828 bytes --]

RE: What can be used instead of /dev/disk/by-path/* symlinks?

[Dorau, Lukasz]

On Tuesday, December 17, 2013 10:41 AM Neil Brown (neilb@suse.de) wrote:
> On Tue, 17 Dec 2013 09:10:44 +0000 "Dorau, Lukasz" <lukasz.dorau@intel.com>
> wrote:
> 
[...]
> Personally, I really don't care.  Does anyone know what udev changed?  Maybe
> we should ask udev developers to change it back.
> 
> NeilBrown
> 

udev developers wrote:
http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-path_id.c#n378

        /*
         * We do not support the ATA transport class, it uses global counters
         * to name the ata devices which numbers spread across multiple
         * controllers.
         *
         * The real link numbers are not exported. Also, possible chains of ports
         * behind port multipliers cannot be composed that way.
         *
         * Until all that is solved at the kernel level, there are no by-path/
         * links for ATA devices.
         */

Lukasz

> >
> > The /dev/disk/by-path/* symlinks are not created for ATA devices in systems using
> systemd v182+, so mdadm cannot use them in case of policies and udev rules
> (mdadm -If --path=...)
> >
> > What do you think - what should be used instead? The symlinks from /sys/block/* ?
> >
> > Regards,
> > Lukasz
> > --

Re: What can be used instead of /dev/disk/by-path/* symlinks?

[Stan Hoeppner]

On 12/17/2013 4:02 AM, Dorau, Lukasz wrote:
> On Tuesday, December 17, 2013 10:41 AM Neil Brown (neilb@suse.de) wrote:
>> On Tue, 17 Dec 2013 09:10:44 +0000 "Dorau, Lukasz" <lukasz.dorau@intel.com>
>> wrote:
>>
> [...]
>> Personally, I really don't care.  Does anyone know what udev changed?  Maybe
>> we should ask udev developers to change it back.
>>
>> NeilBrown
>>
> 
> udev developers wrote:
> http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-path_id.c#n378
> 
>         /*
>          * We do not support the ATA transport class, it uses global counters
>          * to name the ata devices which numbers spread across multiple
>          * controllers.
>          *
>          * The real link numbers are not exported. Also, possible chains of ports
>          * behind port multipliers cannot be composed that way.
>          *
>          * Until all that is solved at the kernel level, there are no by-path/
>          * links for ATA devices.
>          */

I think you should be using libata instead of the old IDE drivers.
Doing so should avoid this problem, if I'm understanding it correctly.

-- 
Stan

Re: What can be used instead of /dev/disk/by-path/* symlinks?

[Dan Williams]

On Tue, Dec 17, 2013 at 2:02 AM, Dorau, Lukasz <lukasz.dorau@intel.com> wrote:
> On Tuesday, December 17, 2013 10:41 AM Neil Brown (neilb@suse.de) wrote:
>> On Tue, 17 Dec 2013 09:10:44 +0000 "Dorau, Lukasz" <lukasz.dorau@intel.com>
>> wrote:
>>
> [...]
>> Personally, I really don't care.  Does anyone know what udev changed?  Maybe
>> we should ask udev developers to change it back.
>>
>> NeilBrown
>>
>
> udev developers wrote:
> http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-path_id.c#n378
>
>         /*
>          * We do not support the ATA transport class, it uses global counters
>          * to name the ata devices which numbers spread across multiple
>          * controllers.
>          *
>          * The real link numbers are not exported. Also, possible chains of ports
>          * behind port multipliers cannot be composed that way.
>          *
>          * Until all that is solved at the kernel level, there are no by-path/
>          * links for ATA devices.
>          */
>

Seems relatively straightforward to add a hardware port number
attribute to the ata_port.  I think the same could be done ata_link,
right?

Re: What can be used instead of /dev/disk/by-path/* symlinks?

[Dimitri John Ledkov]

Hello,

On 17 December 2013 09:10, Dorau, Lukasz <lukasz.dorau@intel.com> wrote:
> Hi Neil,
>
> The /dev/disk/by-path/* symlinks are not created for ATA devices in systems using systemd v182+, so mdadm cannot use them in case of policies and udev rules (mdadm -If --path=...)
>
> What do you think - what should be used instead? The symlinks from /sys/block/* ?
>

I am using a patched udev from systemd daemon collection v204, it
still has "by-path" symlinks setup in the persistent storage rules.
Similarly upstream systemd daemon collection v204 also sets up
"by-path" symlinks in the persistent storage rules.

What is your udev rules config? are any of persistent storage rules
overridden? or not waiting for udev to settle? maybe the "builtin"
command "path_id" not returning / detecting the paths of ATA devices
in question?

-- 
Regards,

Dimitri.

RE: What can be used instead of /dev/disk/by-path/* symlinks?

[Dorau, Lukasz]

On Tuesday, December 17, 2013 10:54 AM Dimitri John Ledkov <xnox@debian.org> wrote:
> 
> Hello,
> 
> On 17 December 2013 09:10, Dorau, Lukasz <lukasz.dorau@intel.com> wrote:
> > Hi Neil,
> >
> > The /dev/disk/by-path/* symlinks are not created for ATA devices in systems using
> systemd v182+, so mdadm cannot use them in case of policies and udev rules
> (mdadm -If --path=...)
> >
> > What do you think - what should be used instead? The symlinks from /sys/block/* ?
> >
> 
> I am using a patched udev from systemd daemon collection v204, it
> still has "by-path" symlinks setup in the persistent storage rules.
> Similarly upstream systemd daemon collection v204 also sets up
> "by-path" symlinks in the persistent storage rules.
> 
> What is your udev rules config? are any of persistent storage rules
> overridden? or not waiting for udev to settle? maybe the "builtin"
> command "path_id" not returning / detecting the paths of ATA devices
> in question?
> 

The /dev/disk/by-path/* symlinks have not been created for ATA devices in systemd since v182:
http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-path_id.c#n378

Lukasz