This patch implements q->lld_busy_fn() for scsi mid layer to export
its busy state for request stacking drivers.
For efficiency, no lock is taken to check the busy state of
shost/starget/sdev, since the returned value is not guaranteed and
may be changed after request stacking drivers call the function,
regardless of taking lock or not.
When scsi can't dispatch I/Os anymore and needs to kill I/Os
(e.g. !sdev), scsi needs to return 'not busy'.
Otherwise, request stacking drivers may hold requests forever.
Signed-off-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx>
Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
---
drivers/scsi/scsi_lib.c | 32 ++++++++++++++++++++++++++++++++
1 files changed, 32 insertions(+)
Index: scsi-post-merge-2.6/drivers/scsi/scsi_lib.c
===================================================================
--- scsi-post-merge-2.6.orig/drivers/scsi/scsi_lib.c
+++ scsi-post-merge-2.6/drivers/scsi/scsi_lib.c
@@ -1465,6 +1465,37 @@ static inline int scsi_host_queue_ready(
}
/*
+ * Busy state exporting function for request stacking drivers.
+ *
+ * For efficiency, no lock is taken to check the busy state of
+ * shost/starget/sdev, since the returned value is not guaranteed and
+ * may be changed after request stacking drivers call the function,
+ * regardless of taking lock or not.
+ *
+ * When scsi can't dispatch I/Os anymore and needs to kill I/Os
+ * (e.g. !sdev), scsi needs to return 'not busy'.
+ * Otherwise, request stacking drivers may hold requests forever.
+ */
+static int scsi_lld_busy(struct request_queue *q)
+{
+ struct scsi_device *sdev = q->queuedata;
+ struct Scsi_Host *shost;
+ struct scsi_target *starget;
+
+ if (!sdev)
+ return 0;
+
+ shost = sdev->host;
+ starget = scsi_target(sdev);
+
+ if (scsi_host_in_recovery(shost) || scsi_host_is_busy(shost) ||
+ scsi_target_is_busy(starget) || scsi_device_is_busy(sdev))
+ return 1;
+
+ return 0;
+}
+
+/*
* Kill a request for a dead device
*/
static void scsi_kill_request(struct request *req, struct request_queue *q)
@@ -1767,6 +1798,7 @@ struct request_queue *scsi_alloc_queue(s
blk_queue_prep_rq(q, scsi_prep_fn);
blk_queue_softirq_done(q, scsi_softirq_done);
blk_queue_rq_timed_out(q, scsi_times_out);
+ blk_queue_lld_busy(q, scsi_lld_busy);
return q;
}
--
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