On Tue, Jan 26 2010 at 1:57pm -0500,
Dave Wysochanski <dwysocha@xxxxxxxxxx> wrote:
> On Tue, 2010-01-26 at 13:48 -0500, Dave Wysochanski wrote:
> > On Tue, 2010-01-26 at 13:09 -0500, Mike Snitzer wrote:
> > > On Tue, Jan 26 2010 at 12:56pm -0500,
> > > Dave Wysochanski <dwysocha@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > > ---
> > > > 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;
> > >
> >
> > Nice simplification Mike, as discussed on IRC.
> >
> > Ack.
> >
>
> Actually, the more I think about it I am not sure about sending the
> uevent in the case where dm_resume() fails. Seems like we should send
> it since the map could have changed - depends on whether we went through
> that 'if (new_map)' block.
Pretty sure we resolved this. As we discussed (just after you sent this
last reply); for the benefit of others:
<dave> so the change uevent here really means "resume was successful"
<mike> yes
<dave> wait - if we suspend it, but resume fails, shouldn't we still
send the event?
<mike> in that case the device will be left suspended; in terms of udev
that's not a "change"
<mike> device is wedged (suspended)
<mike> telling udev about it could just stack up other processes trying
to issue IO to it
<mike> but to be honest I don't know what the purist definition of what
a "change" uevent is; I'm just treating it as telling some blackbox that
DM device has changed and is functional
<dave> that does make sense
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