libata: fix ata_scsi_change_queue_depth()

Fix ata_scsi_change_queue_depth() such that...

* NCQ on/off is exactly determined using the same logic as the issue path.

* queue depth is adjusted to 1 if NCQ is not enabled.

* -EINVAL is returned if requested action is ignored due to limitations.

This fixes the bug which allows queue depth to be increased on
blacklisted NCQ hosts/devices.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 15 insertions, 12 deletions

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index aa6cb6dcec41..48e388800f5a 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -987,29 +987,32 @@ int ata_scsi_change_queue_depth(struct scsi_device *sdev, int queue_depth)
         struct ata_port *ap = ata_shost_to_port(sdev->host);
         struct ata_device *dev;
         unsigned long flags;
-        int max_depth;
 
-        if (queue_depth < 1)
+        if (queue_depth < 1 || queue_depth == sdev->queue_depth)
                 return sdev->queue_depth;
 
         dev = ata_scsi_find_dev(ap, sdev);
         if (!dev || !ata_dev_enabled(dev))
                 return sdev->queue_depth;
 
-        max_depth = min(sdev->host->can_queue, ata_id_queue_depth(dev->id));
-        max_depth = min(ATA_MAX_QUEUE - 1, max_depth);
-        if (queue_depth > max_depth)
-                queue_depth = max_depth;
-
-        scsi_adjust_queue_depth(sdev, MSG_SIMPLE_TAG, queue_depth);
-
+        /* NCQ enabled? */
         spin_lock_irqsave(ap->lock, flags);
-        if (queue_depth > 1)
-                dev->flags &= ~ATA_DFLAG_NCQ_OFF;
-        else
+        dev->flags &= ~ATA_DFLAG_NCQ_OFF;
+        if (queue_depth == 1 || !ata_ncq_enabled(dev)) {
                 dev->flags |= ATA_DFLAG_NCQ_OFF;
+                queue_depth = 1;
+        }
         spin_unlock_irqrestore(ap->lock, flags);
 
+        /* limit and apply queue depth */
+        queue_depth = min(queue_depth, sdev->host->can_queue);
+        queue_depth = min(queue_depth, ata_id_queue_depth(dev->id));
+        queue_depth = min(queue_depth, ATA_MAX_QUEUE - 1);
+
+        if (sdev->queue_depth == queue_depth)
+                return -EINVAL;
+
+        scsi_adjust_queue_depth(sdev, MSG_SIMPLE_TAG, queue_depth);
         return queue_depth;
 }