Re: [PATCH] scsi: libsas: Fix disk not being scanned in after being removed

[yangxingui <yangxingui@xxxxxxxxxx>]

Hi Jason,

On 2024/2/23 15:04, Jason Yan wrote:
> On 2024/2/23 12:04, yangxingui wrote:
> > Hi, John
> >
> > On 2024/2/22 20:41, John Garry wrote:
> > > On 21/02/2024 07:31, Xingui Yang wrote:
> > > > As of commit d8649fc1c5e4 ("scsi: libsas: Do discovery on empty PHY to
> > > > update PHY info"), do discovery will send a new SMP_DISCOVER and update
> > > > phy->phy_change_count. We found that if the disk is reconnected and phy
> > > > change_count changes at this time, the disk scanning process will 
> > > > not be
> > > > triggered.
> > > >
> > > > So update the PHY info with the last query results.
> > > >
> > > > Fixes: d8649fc1c5e4 ("scsi: libsas: Do discovery on empty PHY to 
> > > > update PHY info")
> > > > Signed-off-by: Xingui Yang <yangxingui@xxxxxxxxxx>
> > > > ---
> > > >   drivers/scsi/libsas/sas_expander.c | 9 ++++-----
> > > >   1 file changed, 4 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/drivers/scsi/libsas/sas_expander.c 
> > > > b/drivers/scsi/libsas/sas_expander.c
> > > > index a2204674b680..9563f5589948 100644
> > > > --- a/drivers/scsi/libsas/sas_expander.c
> > > > +++ b/drivers/scsi/libsas/sas_expander.c
> > > > @@ -1681,6 +1681,10 @@ int sas_get_phy_attached_dev(struct 
> > > > domain_device *dev, int phy_id,
> > > >           if (*type == 0)
> > > >               memset(sas_addr, 0, SAS_ADDR_SIZE);
> > > >       }
> > > > +
> > > > +    if ((SAS_ADDR(sas_addr) == 0) || (res == -ECOMM))
> > > > +        sas_set_ex_phy(dev, phy_id, disc_resp);
> > > > +
> > > >       kfree(disc_resp);
> > > >       return res;
> > > >   }
> > > > @@ -1972,11 +1976,6 @@ static int sas_rediscover_dev(struct 
> > > > domain_device *dev, int phy_id,
> > > >       if ((SAS_ADDR(sas_addr) == 0) || (res == -ECOMM)) {
> > > >           phy->phy_state = PHY_EMPTY;
> > > >           sas_unregister_devs_sas_addr(dev, phy_id, last);
> > > > -        /*
> > > > -         * Even though the PHY is empty, for convenience we discover
> > > > -         * the PHY to update the PHY info, like negotiated linkrate.
> > > > -         */
> > > > -        sas_ex_phy_discover(dev, phy_id);
> > >
> > > It would be nice to be able to call sas_set_ex_phy() here (instead of 
> > > sas_get_phy_attached_dev()), but I assume that you can't do that as 
> > > the disc_resp memory is not available.
> > >
> > > If we were to manually set the PHY info here instead, how would that 
> > > look?
> > Yes, I think it is indeed better to use sas_set_ex_phy, as you said, 
> > disc_resp memory is not available. Maybe we can use 
> > sas_get_phy_discover instead of sas_get_phy_attached_dev so we can use 
> > disc_resp?
>
> Can we directly set phy->negotiated_linkrate = SAS_PHY_DISABLED here? 
> For an empty PHY the other variables means nothing, so why bother get 
> and update them?
The value of the negotiated link rate has two possible values ​​in the 
current processing branch: SAS_LINK_RATE_UNKNOWN and SAS_PHY_DISABLED, 
and both come from disc_resp. If we do not use disc_resp, but set a 
fixed value SAS_PHY_DISABLED for it, it may not be appropriate.

Thanks,
Xingui