[PATCH] libata: implement ata_scsi_timed_out()
Implement ata_scsi_timed_out(), to be used as
scsi_host_template->eh_timed_out callback for all libata drivers.
Without this function, the following race exists.
If a qc completes after SCSI timer expires but before libata EH kicks
in, the qc gets completed but the scsicmd still gets passed to libata
EH resulting in ->eng_timeout invocation with NULL qc, which none is
handling properly.
This patch makes sure that scmd and qc share the same lifetime.
Original idea from Jeff Garzik <jgarzik@pobox.com>.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 1df468e..d67cc2f 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -717,6 +717,47 @@
}
/**
+ * ata_scsi_timed_out - SCSI layer time out callback
+ * @cmd: timed out SCSI command
+ *
+ * Handles SCSI layer timeout. We race with normal completion of
+ * the qc for @cmd. If the qc is already gone, we lose and let
+ * the scsi command finish (EH_HANDLED). Otherwise, the qc has
+ * timed out and EH should be invoked. Prevent ata_qc_complete()
+ * from finishing it by setting EH_SCHEDULED and return
+ * EH_NOT_HANDLED.
+ *
+ * LOCKING:
+ * Called from timer context
+ *
+ * RETURNS:
+ * EH_HANDLED or EH_NOT_HANDLED
+ */
+enum scsi_eh_timer_return ata_scsi_timed_out(struct scsi_cmnd *cmd)
+{
+ struct Scsi_Host *host = cmd->device->host;
+ struct ata_port *ap = (struct ata_port *) &host->hostdata[0];
+ unsigned long flags;
+ struct ata_queued_cmd *qc;
+ enum scsi_eh_timer_return ret = EH_HANDLED;
+
+ DPRINTK("ENTER\n");
+
+ spin_lock_irqsave(&ap->host_set->lock, flags);
+ qc = ata_qc_from_tag(ap, ap->active_tag);
+ if (qc) {
+ assert(qc->scsicmd == cmd);
+ qc->flags |= ATA_QCFLAG_EH_SCHEDULED;
+ qc->err_mask |= AC_ERR_TIMEOUT;
+ ret = EH_NOT_HANDLED;
+ }
+ spin_unlock_irqrestore(&ap->host_set->lock, flags);
+
+ DPRINTK("EXIT, ret=%d\n", ret);
+ return ret;
+}
+
+/**
* ata_scsi_error - SCSI layer error handler callback
* @host: SCSI host on which error occurred
*