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[src/trunk]: src/sys Make dksubr use a spin-mutex again, since some drivers s...



details:   https://anonhg.NetBSD.org/src/rev/08f3a7d7f4c7
branches:  trunk
changeset: 340201:08f3a7d7f4c7
user:      mlelstv <mlelstv%NetBSD.org@localhost>
date:      Thu Aug 27 05:51:50 2015 +0000

description:
Make dksubr use a spin-mutex again, since some drivers still call dk_done
from hardware interrupt. Instead, release mutex while calling start routine.

The buffer peek/use/get sequence which can no longer be atomic. So consume
the buffer directly and on error privately save and retry the buffer later.
The dk_drain function is used to flush such a deferred buffer together with
the buffer queue.
Adjust drivers to use dk_drain.

Fix an error path where dk_done was called while the lock was already held.

diffstat:

 sys/arch/xen/xen/xbd_xenbus.c |  15 +++-----
 sys/dev/cgd.c                 |  11 ++----
 sys/dev/dksubr.c              |  73 ++++++++++++++++++++++++++++++++----------
 sys/dev/dkvar.h               |   5 ++-
 sys/dev/ld.c                  |  13 +++----
 5 files changed, 76 insertions(+), 41 deletions(-)

diffs (truncated from 322 to 300 lines):

diff -r 49f1cf2fdc6e -r 08f3a7d7f4c7 sys/arch/xen/xen/xbd_xenbus.c
--- a/sys/arch/xen/xen/xbd_xenbus.c     Thu Aug 27 03:20:13 2015 +0000
+++ b/sys/arch/xen/xen/xbd_xenbus.c     Thu Aug 27 05:51:50 2015 +0000
@@ -1,4 +1,4 @@
-/*      $NetBSD: xbd_xenbus.c,v 1.72 2015/08/16 18:00:03 mlelstv Exp $      */
+/*      $NetBSD: xbd_xenbus.c,v 1.73 2015/08/27 05:51:50 mlelstv Exp $      */
 
 /*
  * Copyright (c) 2006 Manuel Bouyer.
@@ -50,7 +50,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xbd_xenbus.c,v 1.72 2015/08/16 18:00:03 mlelstv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xbd_xenbus.c,v 1.73 2015/08/27 05:51:50 mlelstv Exp $");
 
 #include "opt_xen.h"
 
@@ -363,11 +363,9 @@
                /* Delete all of our wedges. */
                dkwedge_delall(&sc->sc_dksc.sc_dkdev);
 
-               s = splbio();
                /* Kill off any queued buffers. */
-               bufq_drain(sc->sc_dksc.sc_bufq);
+               dk_drain(&sc->sc_dksc);
                bufq_free(sc->sc_dksc.sc_bufq);
-               splx(s);
 
                /* detach disk */
                disk_detach(&sc->sc_dksc.sc_dkdev);
@@ -701,12 +699,11 @@
 next:
                if (bp->b_data != xbdreq->req_data)
                        xbd_unmap_align(xbdreq);
-               disk_unbusy(&sc->sc_dksc.sc_dkdev,
-                   (bp->b_bcount - bp->b_resid),
-                   (bp->b_flags & B_READ));
+
                rnd_add_uint32(&sc->sc_rnd_source,
                    bp->b_blkno);
-               biodone(bp);
+               dk_done(&sc->sc_dksc, bp);
+
                SLIST_INSERT_HEAD(&sc->sc_xbdreq_head, xbdreq, req_next);
        }
 done:
diff -r 49f1cf2fdc6e -r 08f3a7d7f4c7 sys/dev/cgd.c
--- a/sys/dev/cgd.c     Thu Aug 27 03:20:13 2015 +0000
+++ b/sys/dev/cgd.c     Thu Aug 27 05:51:50 2015 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: cgd.c,v 1.103 2015/08/21 09:33:53 christos Exp $ */
+/* $NetBSD: cgd.c,v 1.104 2015/08/27 05:51:50 mlelstv Exp $ */
 
 /*-
  * Copyright (c) 2002 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: cgd.c,v 1.103 2015/08/21 09:33:53 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: cgd.c,v 1.104 2015/08/27 05:51:50 mlelstv Exp $");
 
 #include <sys/types.h>
 #include <sys/param.h>
@@ -565,7 +565,7 @@
                return VOP_IOCTL(cs->sc_tvn, cmd, data, flag, l->l_cred);
        case DIOCGSTRATEGY:
        case DIOCSSTRATEGY:
-               if ((dksc->sc_flags & DKF_INITED) == 0)
+               if (!DK_ATTACHED(dksc))
                        return ENOENT;
                /*FALLTHROUGH*/
        default:
@@ -722,7 +722,6 @@
 static int
 cgd_ioctl_clr(struct cgd_softc *cs, struct lwp *l)
 {
-       int     s;
        struct  dk_softc *dksc = &cs->sc_dksc;
 
        if (!DK_ATTACHED(dksc))
@@ -732,9 +731,7 @@
        dkwedge_delall(&dksc->sc_dkdev);
 
        /* Kill off any queued buffers. */
-       s = splbio();
-       bufq_drain(dksc->sc_bufq);
-       splx(s);
+       dk_drain(dksc);
        bufq_free(dksc->sc_bufq);
 
        (void)vn_close(cs->sc_tvn, FREAD|FWRITE, l->l_cred);
diff -r 49f1cf2fdc6e -r 08f3a7d7f4c7 sys/dev/dksubr.c
--- a/sys/dev/dksubr.c  Thu Aug 27 03:20:13 2015 +0000
+++ b/sys/dev/dksubr.c  Thu Aug 27 05:51:50 2015 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: dksubr.c,v 1.73 2015/08/23 07:47:52 mlelstv Exp $ */
+/* $NetBSD: dksubr.c,v 1.74 2015/08/27 05:51:50 mlelstv Exp $ */
 
 /*-
  * Copyright (c) 1996, 1997, 1998, 1999, 2002, 2008 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: dksubr.c,v 1.73 2015/08/23 07:47:52 mlelstv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: dksubr.c,v 1.74 2015/08/27 05:51:50 mlelstv Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -74,6 +74,7 @@
 
 static void    dk_makedisklabel(struct dk_softc *);
 static int     dk_translate(struct dk_softc *, struct buf *);
+static void    dk_done1(struct dk_softc *, struct buf *, bool);
 
 void
 dk_init(struct dk_softc *dksc, device_t dev, int dtype)
@@ -90,7 +91,7 @@
 void
 dk_attach(struct dk_softc *dksc)
 {
-       mutex_init(&dksc->sc_iolock, MUTEX_DEFAULT, IPL_NONE);
+       mutex_init(&dksc->sc_iolock, MUTEX_DEFAULT, IPL_VM);
        dksc->sc_flags |= DKF_INITED;
 #ifdef DIAGNOSTIC
        dksc->sc_flags |= DKF_WARNLABEL | DKF_LABELSANITY;
@@ -294,41 +295,55 @@
 {
        const struct dkdriver *dkd = dksc->sc_dkdev.dk_driver;
        int error;
-       struct buf *qbp __diagused;
 
        mutex_enter(&dksc->sc_iolock);
 
        if (bp != NULL)
                bufq_put(dksc->sc_bufq, bp);
 
-       while ((bp = bufq_peek(dksc->sc_bufq)) != NULL) {
+       /*
+        * Peeking at the buffer queue and committing the operation
+        * only after success isn't atomic.
+        *
+        * So when a diskstart fails, the buffer is saved
+        * and tried again before the next buffer is fetched.
+        * dk_drain() handles flushing of a saved buffer.
+        *
+        * This keeps order of I/O operations, unlike bufq_put.
+        */
+
+       bp = dksc->sc_deferred;
+       dksc->sc_deferred = NULL;
+
+       if (bp == NULL)
+               bp = bufq_get(dksc->sc_bufq);
+
+       while (bp != NULL) {
 
                disk_busy(&dksc->sc_dkdev);
+               mutex_exit(&dksc->sc_iolock);
                error = dkd->d_diskstart(dksc->sc_dev, bp);
+               mutex_enter(&dksc->sc_iolock);
                if (error == EAGAIN) {
+                       dksc->sc_deferred = bp;
                        disk_unbusy(&dksc->sc_dkdev, 0, (bp->b_flags & B_READ));
                        break;
                }
 
-#ifdef DIAGNOSTIC
-               qbp = bufq_get(dksc->sc_bufq);
-               KASSERT(bp == qbp);
-#else
-               (void) bufq_get(dksc->sc_bufq);
-#endif
-
                if (error != 0) {
                        bp->b_error = error;
                        bp->b_resid = bp->b_bcount;
-                       dk_done(dksc, bp);
+                       dk_done1(dksc, bp, false);
                }
+
+               bp = bufq_get(dksc->sc_bufq);
        }
 
        mutex_exit(&dksc->sc_iolock);
 }
 
-void
-dk_done(struct dk_softc *dksc, struct buf *bp)
+static void
+dk_done1(struct dk_softc *dksc, struct buf *bp, bool lock)
 {
        struct disk *dk = &dksc->sc_dkdev;
 
@@ -340,9 +355,11 @@
                printf("\n");
        }
 
-       mutex_enter(&dksc->sc_iolock);
+       if (lock)
+               mutex_enter(&dksc->sc_iolock);
        disk_unbusy(dk, bp->b_bcount - bp->b_resid, (bp->b_flags & B_READ));
-       mutex_exit(&dksc->sc_iolock);
+       if (lock)
+               mutex_exit(&dksc->sc_iolock);
 
 #ifdef notyet
        rnd_add_uint(&dksc->sc_rnd_source, bp->b_rawblkno);
@@ -351,6 +368,28 @@
        biodone(bp);
 }
 
+void
+dk_done(struct dk_softc *dksc, struct buf *bp)
+{
+       dk_done1(dksc, bp, true);
+}
+
+void
+dk_drain(struct dk_softc *dksc)
+{
+       struct buf *bp;
+
+       mutex_enter(&dksc->sc_iolock);
+       bp = dksc->sc_deferred;
+       if (bp != NULL) {
+               bp->b_error = EIO;
+               bp->b_resid = bp->b_bcount;
+               biodone(bp); 
+       }
+       bufq_drain(dksc->sc_bufq);
+       mutex_exit(&dksc->sc_iolock);
+}
+
 int
 dk_discard(struct dk_softc *dksc, dev_t dev, off_t pos, off_t len)
 {
diff -r 49f1cf2fdc6e -r 08f3a7d7f4c7 sys/dev/dkvar.h
--- a/sys/dev/dkvar.h   Thu Aug 27 03:20:13 2015 +0000
+++ b/sys/dev/dkvar.h   Thu Aug 27 05:51:50 2015 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: dkvar.h,v 1.21 2015/08/16 18:00:03 mlelstv Exp $ */
+/* $NetBSD: dkvar.h,v 1.22 2015/08/27 05:51:50 mlelstv Exp $ */
 
 /*-
  * Copyright (c) 2002 The NetBSD Foundation, Inc.
@@ -47,6 +47,7 @@
        kmutex_t                 sc_iolock;     /* protects buffer queue */
        struct bufq_state       *sc_bufq;       /* buffer queue */
        int                      sc_dtype;      /* disk type */
+       struct buf              *sc_deferred;   /* retry after start failed */
 };
 
 /* sc_flags:
@@ -62,6 +63,7 @@
 #define DKF_TAKEDUMP   0x00200000 /* allow dumping */
 #define DKF_KLABEL      0x00400000 /* keep label on close */
 #define DKF_VLABEL      0x00800000 /* label is valid */
+#define DKF_SLEEP       0x80000000 /* dk_start/dk_done may sleep */
 
 /* Mask of flags that dksubr.c understands, other flags are fair game */
 #define DK_FLAGMASK    0xffff0000
@@ -89,6 +91,7 @@
 int    dk_discard(struct dk_softc *, dev_t, off_t, off_t);
 void   dk_start(struct dk_softc *, struct buf *);
 void   dk_done(struct dk_softc *, struct buf *);
+void   dk_drain(struct dk_softc *);
 int    dk_size(struct dk_softc *, dev_t);
 int    dk_ioctl(struct dk_softc *, dev_t,
                 u_long, void *, int, struct lwp *);
diff -r 49f1cf2fdc6e -r 08f3a7d7f4c7 sys/dev/ld.c
--- a/sys/dev/ld.c      Thu Aug 27 03:20:13 2015 +0000
+++ b/sys/dev/ld.c      Thu Aug 27 05:51:50 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ld.c,v 1.91 2015/08/18 04:20:25 mlelstv Exp $  */
+/*     $NetBSD: ld.c,v 1.92 2015/08/27 05:51:50 mlelstv Exp $  */
 
 /*-
  * Copyright (c) 1998, 2000 The NetBSD Foundation, Inc.
@@ -34,7 +34,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ld.c,v 1.91 2015/08/18 04:20:25 mlelstv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ld.c,v 1.92 2015/08/27 05:51:50 mlelstv Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -197,8 +197,6 @@
        mutex_enter(&sc->sc_mutex);
        sc->sc_maxqueuecnt = 0;
 
-       dk_detach(dksc);
-
        while (sc->sc_queuecnt > 0) {
                sc->sc_flags |= LDF_DRAIN;
                cv_wait(&sc->sc_drain, &sc->sc_mutex);
@@ -224,11 +222,10 @@



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