Re: [PATCH v3] scsi: libsas: Fix exp-attached end device cannot be scanned in again after probe failed

[yangxingui]

Hi, John,

Thanks for your reply.

On 2024/6/18 16:55, John Garry wrote:
> On 13/06/2024 13:23, Xingui Yang wrote:
>
> Sorry for delay in responding and asking further questions.
It doesn't matter.
> > We found that it is judged as broadcast flutter when the exp-attached end
> > device reconnects after probe failed, as follows:
> >
> > [78779.654026] sas: broadcast received: 0
> > [78779.654037] sas: REVALIDATING DOMAIN on port 0, pid:10
> > [78779.654680] sas: ex 500e004aaaaaaa1f phy05 change count has changed
> > [78779.662977] sas: ex 500e004aaaaaaa1f phy05 originated 
> > BROADCAST(CHANGE)
> > [78779.662986] sas: ex 500e004aaaaaaa1f phy05 new device attached
> > [78779.663079] sas: ex 500e004aaaaaaa1f phy05:U:8 attached: 
> > 500e004aaaaaaa05 (stp)
> > [78779.693542] hisi_sas_v3_hw 0000:b4:02.0: dev[16:5] found
> > [78779.701155] sas: done REVALIDATING DOMAIN on port 0, pid:10, res 0x0
> > [78779.707864] sas: Enter sas_scsi_recover_host busy: 0 failed: 0
> > ...
> > [78835.161307] sas: --- Exit sas_scsi_recover_host: busy: 0 failed: 0 
> > tries: 1
> > [78835.171344] sas: sas_probe_sata: for exp-attached device 
> > 500e004aaaaaaa05 returned -19
> > [78835.180879] hisi_sas_v3_hw 0000:b4:02.0: dev[16:5] is gone
> > [78835.187487] sas: broadcast received: 0
> > [78835.187504] sas: REVALIDATING DOMAIN on port 0, pid:10
> > [78835.188263] sas: ex 500e004aaaaaaa1f phy05 change count has changed
> > [78835.195870] sas: ex 500e004aaaaaaa1f phy05 originated 
> > BROADCAST(CHANGE)
> > [78835.195875] sas: ex 500e004aaaaaaa1f rediscovering phy05
> > [78835.196022] sas: ex 500e004aaaaaaa1f phy05:U:A attached: 
> > 500e004aaaaaaa05 (stp)
> > [78835.196026] sas: ex 500e004aaaaaaa1f phy05 broadcast flutter
> > [78835.197615] sas: done REVALIDATING DOMAIN on port 0, pid:10, res 0x0
> >
> > The cause of the problem is that the related ex_phy's 
> > attached_sas_addr was
> > not cleared after the end device probe failed. In order to solve the 
> > above
> > problem, a function sas_ex_unregister_end_dev() is defined to clear the
> > ex_phy information and unregister the end device after the 
> > exp-attached end
> > device probe failed.
>
> Can you just manually clear the ex_phy's attached_sas_addr at the 
> appropiate point (along with calling sas_unregister_dev())? It seems 
> that we are using heavy-handed approach in calling 
> sas_unregister_devs_sas_addr(), which does the clearing and much more.

I just tried it and it worked. If we only clear ex_phy's 
attached_sas_addr, there is no need to call sas_destruct_ports(). We are 
currently using sas_unregister_devs_sas_addr() which will add the port 
to sas_port_del_list, so we need to call sas_destruct_ports() separately 
to delete the port.

Should we also delete the port after the devices probe failed?

Maybe I can update another version and only clear ex_phy's 
attached_sas_addr based on your suggestions.
> > As devices may probe failed after done REVALIDATING DOMAIN when call
> > sas_probe_devices(). Then after its port is added to the 
> > sas_port_del_list,
> > the port will not be deleted until the end of the next REVALIDATING 
> > DOMAIN
> > and sas_destruct_ports() is called. A warning about creating a duplicate
> > port will occur in the new REVALIDATING DOMAIN when the end device
> > reconnects. Therefore, the previous destroy_list and sas_port_del_list
> > should be handled after devices probe failed.
> >
> > Signed-off-by: Xingui Yang <yangxingui@xxxxxxxxxx>
> > ---
> > Changes since v2:
> > - Add a helper for calling sas_destruct_devices() and 
> > sas_destruct_ports(),
> >    and put the new call at the end of sas_probe_devices() based on John's
> >    suggestion.
> >
> > Changes since v1:
> > - Simplify the process of getting ex_phy id based on Jason's suggestion.
> > - Update commit information.
> > ---
> >   drivers/scsi/libsas/sas_discover.c | 32 +++++++++++++++++++-----------
> >   drivers/scsi/libsas/sas_expander.c |  8 ++++++++
> >   drivers/scsi/libsas/sas_internal.h |  6 +++++-
> >   3 files changed, 33 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/scsi/libsas/sas_discover.c 
> > b/drivers/scsi/libsas/sas_discover.c
> > index 8fb7c41c0962..8c517e47d2b9 100644
> > --- a/drivers/scsi/libsas/sas_discover.c
> > +++ b/drivers/scsi/libsas/sas_discover.c
> > @@ -17,6 +17,22 @@
> >   #include <scsi/sas_ata.h>
> >   #include "scsi_sas_internal.h"
> > +static void sas_destruct_ports(struct asd_sas_port *port)
> > +{
> > +    struct sas_port *sas_port, *p;
> > +
> > +    list_for_each_entry_safe(sas_port, p, &port->sas_port_del_list, 
> > del_list) {
> > +        list_del_init(&sas_port->del_list);
> > +        sas_port_delete(sas_port);
> > +    }
> > +}
> > +
> > +static void sas_destruct_devices_and_ports(struct asd_sas_port *port)
>
> "and" in a function name never sounds right.
>
> Can you just call sas_destruct_port(), as it takes a port arg? Maybe 
> rename sas_destruct_ports() to sas_delete_ports(), as it does "delete" - 
> this may avoid some confusion in names.
As described above, if we only clear ex_phy's attached_sas_addr, we do 
not need to call sas_destruct_ports().
Thanks,
Xingui