[dm-devel] dm_ioctl: Only send a change uevent when a resume ioctl changes the device.

[Dave Wysochanski]

On Tue, 2010-01-26 at 13:09 -0500, Mike Snitzer wrote:
> On Tue, Jan 26 2010 at 12:56pm -0500,
> Dave Wysochanski <dwysocha at redhat.com> wrote:
> 
> > Resume ioctls may result in no changes to the device and thus they
> > should not generate change uevents.  For example, if a device is
> > not suspended when a resume ioctl occurs, we should not send a
> > uevent.
> > 
> > Signed-off-by: Dave Wysochanski <dwysocha at redhat.com>
> > ---
> >  drivers/md/dm-ioctl.c |   12 ++++++++----
> >  1 files changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> > index 1d66932..0c1cf53 100644
> > --- a/drivers/md/dm-ioctl.c
> > +++ b/drivers/md/dm-ioctl.c
> > @@ -851,6 +851,7 @@ static int do_suspend(struct dm_ioctl *param)
> >  
> >  static int do_resume(struct dm_ioctl *param)
> >  {
> > +	int send_uevent = 0;
> >  	int r = 0;
> >  	unsigned suspend_flags = DM_SUSPEND_LOCKFS_FLAG;
> >  	struct hash_cell *hc;
> > @@ -895,18 +896,21 @@ static int do_resume(struct dm_ioctl *param)
> >  			set_disk_ro(dm_disk(md), 0);
> >  		else
> >  			set_disk_ro(dm_disk(md), 1);
> > +		send_uevent = 1;
> >  	}
> > -
> > -	if (dm_suspended_md(md))
> > +	if (dm_suspended_md(md)) {
> >  		r = dm_resume(md);
> > +		send_uevent = 1;
> > +	}
> >  
> >  	if (old_map)
> >  		dm_table_destroy(old_map);
> >  
> > -	if (!r) {
> > +	if (send_uevent)
> >  		dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr);
> > +
> > +	if (!r)
> >  		r = __dev_status(md, param);
> > -	}
> >  
> >  	dm_put(md);
> >  	return r;
> 
> Seems you're sending the uevent even if resume failed.  Is that intended?
> 
> Also, can dm_kobject_uevent() come before dm_table_destroy()?
> 
> If so this would be a bit simpler:
> 
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index 1d66932..e3cf568 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -897,16 +897,17 @@ static int do_resume(struct dm_ioctl *param)
>  			set_disk_ro(dm_disk(md), 1);
>  	}
>  
> -	if (dm_suspended_md(md))
> +	if (dm_suspended_md(md)) {
>  		r = dm_resume(md);
> +		if (!r)
> +			dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr);
> +	}
>  
>  	if (old_map)
>  		dm_table_destroy(old_map);
>  
> -	if (!r) {
> -		dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr);
> +	if (!r)
>  		r = __dev_status(md, param);
> -	}
>  
>  	dm_put(md);
>  	return r;
> 
> --
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Nice simplification Mike, as discussed on IRC.

Ack.