Hi,
There was a recent commit in mainline for the scsi devices which do not
respond properly to medium access command:
commit 18a4d0a22ed6c54b67af7718c305cd010f09ddf8
[SCSI] Handle disk devices which can not process medium access commands
We have experienced several devices which fail in a fashion we do not
currently handle gracefully in SCSI. After a failure these devices will
respond to the SCSI primary command set (INQUIRY, TEST UNIT READY, etc.)
but any command accessing the storage medium will time out.
I came across a USB drive which showed similar problem and what I see is
usb storage is still not able to cope with such devices properly.
The control flow downwards is like:
scsi_times_out --> Setting cmd->result as DID_TIME_OUT
scsi_error_handler
scsi_unjam_host
scsi_eh_abort_cmds
command_abort (sets US_FLIDX_TIMED_OUT for us->dflags
calls stop_transport,
and waits for) usb_stor_control_thread (which is waiting for
transport call to return inside
usb_stor_invoke_transport)
both usb_stor_control_thread and
usb_stor_invoke_transport
check for us->dflags timed_out bit and
set the result as DID_ABORT
and signal completion for command_abort
to complete
......
sd_eh_action
checks for cmd->result and finds out that it's DID_ABORT rather than
DID_TIME_OUT.
This patch updates the command result to be TIME_OUT explicitly before
returning from command_abort in scsiglue.c.
I would like to know if this patch can work out for such USB Storage
devices? What would be the better way to do the same?
Regards,
Vishal Annapurve
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From: Vishal Annapurve <vannapurve@xxxxxxxxxx>
Subject: [PATCH] usb-storage: Changing the command result
This change updates the returned result to scsi layer to use
DID_TIMEOUT flag as a result status rather than DID_ABORT for
commands aborted due to timeout.
Signed-off-by: Vishal Annapurve <vannapurve@xxxxxxxxxx>
---
drivers/usb/storage/scsiglue.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index a74e9d8..e7b532e 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -353,6 +353,15 @@ static int command_abort(struct scsi_cmnd *srb)
/* Wait for the aborted command to finish */
wait_for_completion(&us->notify);
+ /* Given that this bit would be only set in case of timedout
+ * command, we can return with DID_TIME_OUT, as scsi layer needs
+ * to use this result rather than DID_ABORT.
+ * This is a WR to avoid removing DID_ABORT altogether
+ * and before the final control goes to scsi layer change the
+ * result to be timedout.
+ */
+ us->srb->result = DID_TIME_OUT << 16;
+
return SUCCESS;
}
--
1.8.4
