[src/trunk]: src/sys/dev/ata In some case, when an error is reported by the d...

[bouyer <bouyer%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/26359e13b5f3
branches:  trunk
changeset: 779900:26359e13b5f3
user:      bouyer <bouyer%NetBSD.org@localhost>
date:      Tue Jun 26 09:49:24 2012 +0000

description:
In some case, when an error is reported by the disk, the ahci controller
still reports a number of bytes transfered equal to bcount.
This then triggers a KASSERT in physio_biodone:
        if (done == todo)
                KASSERT(bp->b_error == 0);
Detect this case in wd(4) (so that the workaround works for other controllers
too if they have the same issue, or if the issue is with the drive)
and claim we didn't read/write anything.

diffstat:

 sys/dev/ata/wd.c |  12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diffs (33 lines):

diff -r 4db931654d1a -r 26359e13b5f3 sys/dev/ata/wd.c
--- a/sys/dev/ata/wd.c  Tue Jun 26 02:05:43 2012 +0000
+++ b/sys/dev/ata/wd.c  Tue Jun 26 09:49:24 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: wd.c,v 1.392 2012/02/02 19:43:02 tls Exp $ */
+/*     $NetBSD: wd.c,v 1.393 2012/06/26 09:49:24 bouyer Exp $ */
 
 /*
  * Copyright (c) 1998, 2001 Manuel Bouyer.  All rights reserved.
@@ -54,7 +54,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: wd.c,v 1.392 2012/02/02 19:43:02 tls Exp $");
+__KERNEL_RCSID(0, "$NetBSD: wd.c,v 1.393 2012/06/26 09:49:24 bouyer Exp $");
 
 #include "opt_ata.h"
 
@@ -819,6 +819,14 @@
                bp->b_error = EIO;
                break;
        }
+       if (__predict_false(bp->b_error != 0) && bp->b_resid == 0) {
+               /*
+                * the disk or controller sometimes report a complete
+                * xfer, when there has been an error. This is wrong,
+                * assume nothing got transfered in this case
+                */
+               bp->b_resid = bp->b_bcount;
+       }
        disk_unbusy(&wd->sc_dk, (bp->b_bcount - bp->b_resid),
            (bp->b_flags & B_READ));
        rnd_add_uint32(&wd->rnd_source, bp->b_blkno);