Hello, Luben, Patrick.
Patrick Mansfield wrote:
On Wed, Apr 12, 2006 at 01:24:42AM -0700, Luben Tuikov wrote:
--- Tejun Heo <htejun@xxxxxxxxx> wrote:
Patrick Mansfield wrote:
On Tue, Apr 11, 2006 at 01:41:57PM -0400, Jeff Garzik wrote:
Tejun Heo wrote:
+int scsi_eh_schedule_cmd(struct scsi_cmnd *scmd)
Per other email it should be called scsi_req_abort_cmd() or such, as that
is the only reason to call it, correct?
Well, it's named this way is to keep it consistent with
scsi_eh_schedule_host(). Either name is okay with me but driver which
use this function probably have interest in schedule_host() but not in
other SCSI EH functions. So, considering that, I think the current
naming is okay.
Tejun, note that scsi_req_abort_cmd() absolves your patch.
I think this is what Pat is trying to say. I.e. it is much
more general and thus applies to more applications (as in uses).
Plus it is shorter, simpler (3 lines) and more straightforward.
Yeap, I kind of misunderstood Patrick's mail. scsi_req_abort_cmd() is
good but...
* The event is not really a timeout. It shouldn't be logged as
TIMEOUT_ERROR or completed with DID_TIME_OUT when add_scmd fails.
* Similarly, I don't think it's a good idea to call ->eh_timed_out() on
explicit command abort. If something common has to be done, it's better
to make a function for that can calling the function from both
->eh_timed_out() and after scsi_req_abort_cmd() succeeds. Otherwise,
libata has to decide whether ->eh_timed_out() is called from real
timeout or explicit abortion and skip timeout processing for explicit
abortions.
* I don't really understand what you mean by saying scsi_req_abort_cmd()
is more generic. If it means the WARN_ON(!->eh_strategy_handler) part.
That's just a safety net as standard SCSI doesn't know what to do with
commands directly aborted by LLDD. If it's something else, please
elaborate.
Both implementations work ... really I'd prefer a scsi_times_out() and
scsi_abort_cmd() that call a __scsi_abort_cmd().
__scsi_abort_cmd() would just contain scmd_add, I think.
If we implement them right, in the future those simple interfaces can stay
the same even if we no longer have to invoke eh to abort a command.
So, scsi_eh_reschedule_host() is equivalent to simply scsi_req_abort_cmd(cmd)
xor scsi_req_dev_reset(dev), the latter in case you want to notify without
piggybacking on a command.
Can you please post the patch for scsi_req_dev_reset()? One thing to
note is that libata might not have sdev to call that function with when
it wants to invoke EH for hotplug.
Also, your routine calls more specific eh routines and you should try
to be more general.
Please, elaborate.
Any other handling can be completed by calling the ->done function.
Even the abort/cancel could be done in the driver without this, I assume
it is avaiable so the driver can use the eh process and existing code
paths rather than duplicate similar code.
Yeap, as I noted earlier, passing scmds to EH is possible without this
function but it has to be done in a quite hackish way. My earlier
I didn't mean pass them to eh, I mean the driver or transport could have
its own work queue (or not ... we don't need a work queue or process
context to send commands, scsi core sends commands without a work queue or
process context), and issue the abort. Then on completion set error to
DID_TIME_OUT (or whatever makes sense) and call the ->done function.
We should move towards driver/transport supplied eh, that is invoked by
the driver/transport specific code, not (possibly) by a single timeout. I
thought this was the direction everyone wanted to go.
I think it's good have some infrastructure in SCSI. e.g. libata can do
everything itself but it's just nice to have SCSI EH infrastructure to
build upon (EH thread, scmd draining & plugging...).
Thanks.
--
tejun
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