Re: [REGRESSION 3.17] scsi (uas) disks no longer using tagged command queuing

[Christoph Hellwig <hch@infradead.org>]

On Wed, Sep 10, 2014 at 09:21:24AM +0200, Hans de Goede wrote:
> I've applied the patch, this results in the following new dmesg output
> when using uas:
> 
> [  120.602632] initialized host-wide tag map!
> 
> Thank you for looking into this.

So we're initializing the tag map, but scsi_activate_tcq doesn't pick it
up.  I can't really come up with a good explanation for it, but there
even without that there is an elephant in the room:  as part of the
scsi-mq series I moved the bqt field used for this into a union with the
new blk_mq_tag_set.  Below is a patch to get rid of that union, can you
try if that fixes it?


diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index d0f69a3..bcffff2 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -584,10 +584,8 @@ struct Scsi_Host {
 	 * Area to keep a shared tag map (if needed, will be
 	 * NULL if not).
 	 */
-	union {
-		struct blk_queue_tag	*bqt;
-		struct blk_mq_tag_set	tag_set;
-	};
+	struct blk_queue_tag	*bqt;
+	struct blk_mq_tag_set	tag_set;
 
 	atomic_t host_busy;		   /* commands actually active on low-level */
 	atomic_t host_blocked;