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firewire: fw-sbp2: enforce a retry of __scsi_add_device if bus generation changed

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fw-sbp2 is unable to reconnect while performing __scsi_add_device
because there is only a single workqueue thread context available for
both at the moment.  This should be fixed eventually.

An actual failure of __scsi_add_device is easy to handle, but an
incomplete execution of __scsi_add_device with an sdev returned would
remain undetected and leave the SBP-2 target unusable.

Therefore we use a workaround:  If there was a bus reset during
__scsi_add_device (i.e. during the SCSI probe), we remove the new sdev
immediately, log out, and attempt login and SCSI probe again.

Tested-by: Jarod Wilson <jwilson@redhat.com> (earlier version)
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Stefan Richter 2008-02-15 21:29:02 +01:00
parent 7bb6bf7c8b
commit e80de3704a
1 changed files with 35 additions and 14 deletions
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49
drivers/firewire/fw-sbp2.c
View file

@ -762,22 +762,43 @@ static void sbp2_login(struct work_struct *work)
sdev = __scsi_add_device(shost, 0, 0,
scsilun_to_int(&eight_bytes_lun), lu);
if (IS_ERR(sdev)) {
smp_rmb(); /* generation may have changed */
generation = device->generation;
smp_rmb(); /* node_id must not be older than generation */
/*
* FIXME: We are unable to perform reconnects while in sbp2_login().
* Therefore __scsi_add_device() will get into trouble if a bus reset
* happens in parallel. It will either fail or leave us with an
* unusable sdev. As a workaround we check for this and retry the
* whole login and SCSI probing.
*/
sbp2_send_management_orb(lu, device->node_id, generation,
SBP2_LOGOUT_REQUEST, lu->login_id, NULL);
/*
* Set this back to sbp2_login so we fall back and
* retry login on bus reset.
*/
PREPARE_DELAYED_WORK(&lu->work, sbp2_login);
} else {
lu->sdev = sdev;
scsi_device_put(sdev);
/* Reported error during __scsi_add_device() */
if (IS_ERR(sdev))
goto out_logout_login;
scsi_device_put(sdev);
/* Unreported error during __scsi_add_device() */
smp_rmb(); /* get current card generation */
if (generation != device->card->generation) {
scsi_remove_device(sdev);
goto out_logout_login;
}
/* No error during __scsi_add_device() */
lu->sdev = sdev;
goto out;
out_logout_login:
smp_rmb(); /* generation may have changed */
generation = device->generation;
smp_rmb(); /* node_id must not be older than generation */
sbp2_send_management_orb(lu, device->node_id, generation,
SBP2_LOGOUT_REQUEST, lu->login_id, NULL);
/*
* If a bus reset happened, sbp2_update will have requeued
* lu->work already. Reset the work from reconnect to login.
*/
PREPARE_DELAYED_WORK(&lu->work, sbp2_login);
out:
sbp2_target_put(tgt);
}