Re: 2.6.27-rc1 (2fca5c): libata: kernel cant boot

[Jens Axboe <jens.axboe@oracle.com>]

On Fri, Oct 24 2008, Paul Mundt wrote:
> On Fri, Oct 24, 2008 at 09:13:29AM +0200, Jens Axboe wrote:
> > On Fri, Oct 24 2008, Jens Axboe wrote:
> > > On Fri, Oct 24 2008, Alexander Beregalov wrote:
> > > > Hi
> > > > 
> > > > commit 2fca5ccf97d2c28bcfce44f5b07d85e74e3cd18e
> > > > Author: Jens Axboe <jens.axboe@oracle.com>
> > > > Date:   Wed Oct 22 09:34:49 2008 +0200
> > > > 
> > > >     libata: switch to using block layer tagging support
> > > > 
> > > > 
> > > > This kernel can not read even 0 sector on disk with rootfs. It
> > > > initialized disk, but cant read it at all.
> > > >  CMD646 on Sparc
> > > > 
> > > > Rverting helped.
> > > 
> > > Doh, how annoying! What driver does that controller use? PATA doesn't
> > > even use NCQ, so it's a bit of an oddity that it makes a difference at
> > > all.
> > > 
> > > Can you provide the boot messages?
> > 
> > Darn, this smells like a train wreck. I'm assuming this fixes it?
> > 
> Yes, that fixes it.

OK, that's pretty bad. 2.6.28-rc1 will not work on any box using libata
with non-ncq disks. If you need me, I'll be at the bar.

----------

>From e598055dde1951c47c8b3522616f6ebff0ed9847 Mon Sep 17 00:00:00 2001
From: Jens Axboe <jens.axboe@oracle.com>
Date: Fri, 24 Oct 2008 09:22:42 +0200
Subject: [PATCH] libata: fix bug with non-ncq devices

The recent commit 201f1b98822078c808b5e2d379a6ddbfc0a06ee1 to enable
support for block layer tagging in libata was broken for non-NCQ
devices. The block layer initializes the tag field to -1 to detect
invalid uses of a tag, and if the libata devices does NOT support
NCQ, we just used that field to index the internal command list.
So we need to check for -1 first and only use the tag field if
it's valid.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
 drivers/ata/libata-scsi.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index d5b9b72..4b95c43 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -708,7 +708,11 @@ static struct ata_queued_cmd *ata_scsi_qc_new(struct ata_device *dev,
 {
 	struct ata_queued_cmd *qc;
 
-	qc = ata_qc_new_init(dev, cmd->request->tag);
+	if (cmd->request->tag != -1)
+		qc = ata_qc_new_init(dev, cmd->request->tag);
+	else
+		qc = ata_qc_new_init(dev, 0);
+
 	if (qc) {
 		qc->scsicmd = cmd;
 		qc->scsidone = done;
-- 
1.6.0.2.588.g3102


-- 
Jens Axboe