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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 08-08-2012, 07:31 PM
Mike Snitzer
 
Default scsi_dh_rdac: Add empty set_params function to scsi_dh_rdac

On Wed, Aug 08 2012 at 12:10pm -0400,
Moger, Babu <Babu.Moger@netapp.com> wrote:

> This patch adds empty set_params function to scsi_dh_rdac.
>
> This patch is required for the following features to work properly.
> 1. add retain_attached_hw_handler feature
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=a58a935d5a1b2ad267017a68c3a1b ca26226cc76
>
> 2. add scsi_dh_attached_handler_name
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=7e8a74b177f17d100916b6ad41545 0f7c9508691
>
>
> DM layer detaches the handler if the set_params is not implemented or fails.
>
> For example if we pass following parameters from multipath:
>
> features "1 retain_attached_hw_handler" (consider rdac as attached_hw_handler)
> hardware_handler "2 alua 1"
>
> If the attached_hw_handler is rdac, then DM anyway tries to call set_params on rdac. Because rdac does not
> implement set_params, scsi_dh_set_params fails and DM detaches the handler.
>
> This patch fixes this problem.
>
> Signed-off-by: Babu Moger <babu.moger@netapp.com>

I think it'd be best to fix scsi_dh_set_params() so that it returns 0 if
scsi_dh->set_params is NULL. That'd avoid all scsi_dh from having to
stub out a similar set_params to return 0.

But taking a step back, have you actually seen the problem you're saying
this patch fixes?

This problem shouldn't exist:
drivers/md/dm-mpath.carse_path will free m->hw_handler_params (and
reset it to NULL) if a scsi_dh is already attached. Have a look at the
if (attached_handler_name) {} case.

Mike

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Old 08-08-2012, 09:34 PM
"Moger, Babu"
 
Default scsi_dh_rdac: Add empty set_params function to scsi_dh_rdac

> -----Original Message-----
> From: Mike Snitzer [mailto:snitzer@redhat.com]
> Sent: Wednesday, August 08, 2012 2:31 PM
> To: Moger, Babu
> Cc: linux-scsi; device-mapper development (dm-devel@redhat.com)
> Subject: Re: scsi_dh_rdac: Add empty set_params function to scsi_dh_rdac
>
> On Wed, Aug 08 2012 at 12:10pm -0400,
> Moger, Babu <Babu.Moger@netapp.com> wrote:
>
> > This patch adds empty set_params function to scsi_dh_rdac.
> >
> > This patch is required for the following features to work properly.
> > 1. add retain_attached_hw_handler feature
> >
> >
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=a58a
> 935d5a1b2ad267017a68c3a1bca26226cc76
> >
> > 2. add scsi_dh_attached_handler_name
> >
> >
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=7e8
> a74b177f17d100916b6ad415450f7c9508691
> >
> >
> > DM layer detaches the handler if the set_params is not implemented or
> fails.
> >
> > For example if we pass following parameters from multipath:
> >
> > features "1 retain_attached_hw_handler" (consider rdac as
> attached_hw_handler)
> > hardware_handler "2 alua 1"
> >
> > If the attached_hw_handler is rdac, then DM anyway tries to call
> set_params on rdac. Because rdac does not
> > implement set_params, scsi_dh_set_params fails and DM detaches the
> handler.
> >
> > This patch fixes this problem.
> >
> > Signed-off-by: Babu Moger <babu.moger@netapp.com>
>
> I think it'd be best to fix scsi_dh_set_params() so that it returns 0 if
> scsi_dh->set_params is NULL. That'd avoid all scsi_dh from having to
> stub out a similar set_params to return 0.
>
> But taking a step back, have you actually seen the problem you're saying
> this patch fixes?
>
> This problem shouldn't exist:
> drivers/md/dm-mpath.carse_path will free m->hw_handler_params (and
> reset it to NULL) if a scsi_dh is already attached. Have a look at the
> if (attached_handler_name) {} case.

My bad. I was still using one of your old patches.
http://www.redhat.com/archives/dm-devel/2012-June/msg00174.html

Things have changed after this version. We don't have this problem with the new set of patches.


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