Date:
From: Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx>
Subject: firewire: fw-sbp2: enforce a retry of __scsi_add_device if bus generation changed
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.
Signed-off-by: Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx>
---
The previous patch "firewire: fw-sbp2: retry login if scsi_device was
offlined early" should be folded into this one before upstream
submission.
drivers/firewire/fw-sbp2.c | 43 ++++++++++++++++---------------------
1 file changed, 19 insertions(+), 24 deletions(-)
Index: linux/drivers/firewire/fw-sbp2.c
===================================================================
--- linux.orig/drivers/firewire/fw-sbp2.c
+++ linux/drivers/firewire/fw-sbp2.c
@@ -824,36 +824,31 @@ static void sbp2_login(struct work_struc
sdev = __scsi_add_device(shost, 0, 0,
scsilun_to_int(&eight_bytes_lun), lu);
- if (IS_ERR(sdev)) {
- /*
- * The most frequent cause for __scsi_add_device() to fail
- * is a bus reset while sending the SCSI INQUIRY. Try again.
- */
+ /*
+ * 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.
+ */
+
+ if (IS_ERR(sdev))
goto out_logout_login;
- } else if (sdev->sdev_state == SDEV_OFFLINE) {
- /*
- * 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 (that's OK, see above) or take sdev
- * offline. Here is a crude workaround for the latter.
- */
- scsi_device_put(sdev);
+ scsi_device_put(sdev);
+
+ smp_rmb(); /* get current card generation */
+ if (generation != device->card->generation) {
scsi_remove_device(sdev);
goto out_logout_login;
-
- } else {
- /*
- * Can you believe it? Everything went well.
- */
- lu->sdev = sdev;
- smp_wmb(); /* We need lu->sdev when we want to block lu. */
- atomic_dec(&lu->tgt->dont_block);
- scsi_device_put(sdev);
- goto out;
}
+ /* Everything went well. */
+ lu->sdev = sdev;
+ smp_wmb(); /* We need lu->sdev when we want to block lu. */
+ atomic_dec(&lu->tgt->dont_block);
+ goto out;
+
out_logout_login:
smp_rmb(); /* generation may have changed */
generation = device->generation;
--
Stefan Richter
-=====-==--- --=- -=---
http://arcgraph.de/sr/
-
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