James Bottomley wrote:
On Wed, 2004-09-29 at 14:02, Luben Tuikov wrote:
According to Documentation/scsi/scsi_mid_low_api.txt, the only possible
error returns are SCSI_MLQUEUE_DEVICE_BUSY and SCSI_MLQUEUE_HOST_BUSY.
Neither is appropriate; should the second one be returned?
I believe internally SCSI Core returns DID_ERROR.
For a device that no-longer exists, DID_NO_CONNECT is probably the most
appropriately descriptive.
Does this mean that scsi_device_cancel() should set the result
code to DID_NO_CONNECT either?
This would involve a race, because it's possible for
queuecommand to accept a command and then scsi_remove_host() to be called
before the command is carried out.
Correct, scsi_remove_host() is asynchronous ... you can get requests
after calling it while the queue is halting ... you must error these.
If the command belongs to the LLDD, why does scsi_remove_host do the
following:
calls scsi_host_cancel,
which calls scsi_device_cancel_cb for each device,
which calls scsi_device_cancel,
which calls scsi_finish_command for each active command,
which passes the command back to the upper layer
Either there's a bug in the host removal sequence, or else the LLDD
doesn't own any requests once scsi_remove_host has been called.
Right. scsi_remove_host tells the mid-layer that it's OK to trash all
inflight commands because you removed all their users before calling
it. It also tells us that you won't accept any future commands for this
host (because you'll error any attempt in queuecommand).
Do you mean to say that when scsi_remove_host() is called,
the LLDD must no own any commands? This is good, it means
that the LLDD plugged queuecommand(), did "recovery" of
pending commands and is ready for slave_destroy().
But does this also mean that scsi_device_cancel() (cancel_pending_io)
is unnecessary in the scsi_remove_host() path as there's no
outstanding IO to the host?
Luben
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