On Wed, 2012-02-29 at 16:28 -0800, Dan Williams wrote:
> On Wed, Feb 29, 2012 at 2:05 PM, James Bottomley
> <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > On Fri, 2012-02-10 at 00:45 -0800, Dan Williams wrote:
> >> The strategy handlers may be called in places that are problematic for
> >> libsas (i.e. sata resets outside of domain revalidation filtering /
> >> libata link recovery), or problematic for userspace (non-blocking ioctl
> >> to sleeping reset functions). However, these routines are also called
> >> for eh escalations and recovery of scsi_eh_prep_cmnd(), so permit them
> >> as long as we are running in the host's error handler.
> >>
> >> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> >> ---
> >> drivers/scsi/libsas/sas_scsi_host.c | 15 +++++++++++----
> >> 1 files changed, 11 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/scsi/libsas/sas_scsi_host.c b/drivers/scsi/libsas/sas_scsi_host.c
> >> index f0b9b7b..1cabedc 100644
> >> --- a/drivers/scsi/libsas/sas_scsi_host.c
> >> +++ b/drivers/scsi/libsas/sas_scsi_host.c
> >> @@ -463,11 +463,14 @@ EXPORT_SYMBOL_GPL(sas_get_local_phy);
> >> /* Attempt to send a LUN reset message to a device */
> >> int sas_eh_device_reset_handler(struct scsi_cmnd *cmd)
> >> {
> >> - struct domain_device *dev = cmd_to_domain_dev(cmd);
> >> - struct sas_internal *i =
> >> - to_sas_internal(dev->port->ha->core.shost->transportt);
> >> - struct scsi_lun lun;
> >> int res;
> >> + struct scsi_lun lun;
> >> + struct Scsi_Host *host = cmd->device->host;
> >> + struct domain_device *dev = cmd_to_domain_dev(cmd);
> >> + struct sas_internal *i = to_sas_internal(host->transportt);
> >> +
> >> + if (current != host->ehandler)
> >> + return FAILED;
> >
> > Doing this will ensure that SG_SCSI_RESET now fails.
> >
> > I don't mind checking for O_NONBLOCK in the sg handler and failing if it
> > is, but disallowing everything looks a trifle drastic.
> >
>
> The thought process here was following the lead of libata which does
> not specify eh_reset handlers. We can't permit "unmanaged" (outside
> of eh) resets to hit ata devices otherwise we run the risk of a reset
> turning into a link bounce / hotplug.
>
> ...and I can't take the same route as I did for the scsi_transport_sas
> initiated reset since these handlers are called from both ioctl and eh
> context, or can I?
>
> Hmm, what about something like:
>
> if (current != host->ehandler) {
> schedule_reset_to_run_in_eh_context():
> wait_for_eh();
> } else
> do_reset();
I think that would work for me ... as long as the wait doesn't cause
entangled deadlocks (I can't think of any at the moment, but I'll think
a bit more deeply about it).
James
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