[src/jdolecek-ncq]: src/sys/dev/ata put back reset of retry count to 0 when s...

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

details:   https://anonhg.NetBSD.org/src/rev/9aa958a740b3
branches:  jdolecek-ncq
changeset: 822922:9aa958a740b3
user:      jdolecek <jdolecek%NetBSD.org@localhost>
date:      Wed Jun 14 20:17:46 2017 +0000

description:
put back reset of retry count to 0 when starting processing a buf

do not use NCQ for retried transfers to speed up recovery, unless FUA
is requested

diffstat:

 sys/dev/ata/wd.c |  18 ++++++++++++++----
 1 files changed, 14 insertions(+), 4 deletions(-)

diffs (46 lines):

diff -r b7afd1b1d12c -r 9aa958a740b3 sys/dev/ata/wd.c
--- a/sys/dev/ata/wd.c  Tue Jun 13 19:15:32 2017 +0000
+++ b/sys/dev/ata/wd.c  Wed Jun 14 20:17:46 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: wd.c,v 1.428.2.14 2017/04/24 22:20:23 jdolecek Exp $ */
+/*     $NetBSD: wd.c,v 1.428.2.15 2017/06/14 20:17:46 jdolecek 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 1.428.2.14 2017/04/24 22:20:23 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: wd.c,v 1.428.2.15 2017/06/14 20:17:46 jdolecek Exp $");
 
 #include "opt_ata.h"
 
@@ -650,6 +650,7 @@
                bp = bufq_get(wd->sc_q);
                KASSERT(bp != NULL);
 
+               xfer->c_bio.retries = 0;
                wdstart1(wd, bp, xfer);
        }
 
@@ -685,8 +686,17 @@
            ((xfer->c_bio.bcount / wd->sc_dk.dk_label->d_secsize) > 128)))
                xfer->c_bio.flags |= ATA_LBA48;
 
-       /* If NCQ was negotiated, always use it */
-       if (wd->drvp->drive_flags & ATA_DRIVE_NCQ) {
+       /*
+        * If NCQ was negotiated, always use it for the first attempt.
+        * Since device cancels all outstanding requests on error, downgrade
+        * to non-NCQ on retry, so that the retried transfer would not cause
+        * cascade failure for the other transfers if it fails again.
+        * If FUA was requested, we can't downgrade, as that would violate
+        * the semantics - FUA would not be honored. In that case, continue
+        * retrying with NCQ.
+        */
+       if (wd->drvp->drive_flags & ATA_DRIVE_NCQ &&
+           (xfer->c_bio.retries == 0 || (bp->b_flags & B_MEDIA_FUA))) {
                xfer->c_bio.flags |= ATA_LBA48;
                xfer->c_flags |= C_NCQ;