Re: [PATCH] libata/sas: only set FROZEN flag if new EH is supported

Nishanth Aravamudan
2011-06-21T16:07:43Z

Ping on this -- Tejun, Brian, Jeff, this is a pretty annoying 2.6.39
regression which it would be good to have fixed in 3.0.

Thanks,
Nish

On 16.06.2011 [08:28:36 -0700], Nishanth Aravamudan wrote:
> On 16.06.2011 [08:28:39 -0500], Brian King wrote:
> > On 06/16/2011 02:51 AM, Tejun Heo wrote:
> > > On Wed, Jun 15, 2011 at 04:34:17PM -0700, Nishanth Aravamudan wrote:
> > >>> That looks like the right thing to do. For ipr's usage of
> > >>> libata, we don't have the concept of a port frozen state, so this flag
> > >>> should really never get set. The alternate way to fix this would be to
> > >>> only set ATA_PFLAG_FROZEN in ata_port_alloc if ap->ops->error_handler
> > >>> is not NULL.
> > >>
> > >> It seemed like ipr is as you say, but I wasn't sure if it was
> > >> appropriate to make the change above in the common libata-scis code or
> > >> not. I don't want to break some other device on accident.
> > >>
> > >> Also, I tried your suggestion, but I don't think that can happen in
> > >> ata_port_alloc? ata_port_alloc is allocated ap itself, and it seems like
> > >> ap->ops typically gets set only after ata_port_alloc returns?
> > >
> > > Maybe we can test error_handler in ata_sas_port_start()?
> >
> > Good point. Since libsas is converted to the new eh now, we would need to have
> > this test.
>
> Commit 7b3a24c57d2eeda8dba9c205342b12689c4679f9 ("ahci: don't enable
> port irq before handler is registered") caused a regression for CD-ROMs
> attached to the IPR SATA bus on Power machines:
>
> ata_port_alloc: ENTER
> ata_port_probe: ata1: bus probe begin
> ata1.00: ata_dev_read_id: ENTER
> ata1.00: failed to IDENTIFY (I/O error, err_mask=0x40)
> ata1.00: ata_dev_read_id: ENTER
> ata1.00: failed to IDENTIFY (I/O error, err_mask=0x40)
> ata1.00: limiting speed to UDMA7:PIO5
> ata1.00: ata_dev_read_id: ENTER
> ata1.00: failed to IDENTIFY (I/O error, err_mask=0x40)
> ata1.00: disabled
> ata_port_probe: ata1: bus probe end
> scsi_alloc_sdev: Allocation failure during SCSI scanning, some SCSI devices might not be configured
>
> The FROZEN flag added in that commit is only cleared by the new EH code,
> which is not used by ipr. Clear this flag in the SAS code if we don't
> support new EH.
>
> Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
>
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index d51f979..ebe1685 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -3797,6 +3797,12 @@ EXPORT_SYMBOL_GPL(ata_sas_port_alloc);
> */
> int ata_sas_port_start(struct ata_port *ap)
> {
> + /*
> + * the port is marked as frozen at allocation time, but if we don't
> + * have new eh, we won't thaw it
> + */
> + if (!ap->ops->error_handler)
> + ap->pflags &= ~ATA_PFLAG_FROZEN;
> return 0;
> }
> EXPORT_SYMBOL_GPL(ata_sas_port_start);
>
>
> --
> Nishanth Aravamudan <nacc@us.ibm.com>
> IBM Linux Technology Center

--
Nishanth Aravamudan <nacc@us.ibm.com>