[src/trunk]: src/sys/dev/dkwedge dk(4): Use disk_begindetach and rely on vdev...

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

details:   https://anonhg.NetBSD.org/src/rev/3f5966c489d1
branches:  trunk
changeset: 374389:3f5966c489d1
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Fri Apr 21 18:30:52 2023 +0000

description:
dk(4): Use disk_begindetach and rely on vdevgone to close instances.

The first step is to decide whether we can detach (if forced, yes; if
not forced, only if not already open), and prevent new opens if so.
There's no need to start closing open instances at this point --
we're just making a decision to detach, and preventing new opens by
transitioning state that dkopen will respect[*].

The second step is to force all open instances to close.  This is
done by vdevgone.  By the time vdevgone returns, there can be no open
instances, so if there _were_ any, closing them via vdevgone will
have passed through dklastclose.

After that point, there can be no opens and no I/O operations, so
dk_openmask must already be zero and the bufq must be empty.

Thus, there's no need to have an explicit call to dklastclose (via
dkwedge_cleanup_parent) before or after making the decision to
detach.

[*] Currently access to this state is racy: nothing serializes
    dkwedge_detach's state transition with dkopen's test.  TBD in a
    separate commit shortly.

diffstat:

 sys/dev/dkwedge/dk.c |  43 +++++++++++++++----------------------------
 1 files changed, 15 insertions(+), 28 deletions(-)

diffs (85 lines):

diff -r 79e523a67310 -r 3f5966c489d1 sys/dev/dkwedge/dk.c
--- a/sys/dev/dkwedge/dk.c      Fri Apr 21 18:30:32 2023 +0000
+++ b/sys/dev/dkwedge/dk.c      Fri Apr 21 18:30:52 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: dk.c,v 1.142 2023/04/21 18:30:32 riastradh Exp $       */
+/*     $NetBSD: dk.c,v 1.143 2023/04/21 18:30:52 riastradh Exp $       */
 
 /*-
  * Copyright (c) 2004, 2005, 2006, 2007 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: dk.c,v 1.142 2023/04/21 18:30:32 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: dk.c,v 1.143 2023/04/21 18:30:52 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_dkwedge.h"
@@ -108,7 +108,6 @@ static void dkminphys(struct buf *);
 
 static int     dkfirstopen(struct dkwedge_softc *, int);
 static void    dklastclose(struct dkwedge_softc *);
-static int     dkwedge_cleanup_parent(struct dkwedge_softc *, int);
 static int     dkwedge_detach(device_t, int);
 static void    dkwedge_delall1(struct disk *, bool);
 static int     dkwedge_del1(struct dkwedge_info *, int);
@@ -668,28 +667,6 @@ dkwedge_del1(struct dkwedge_info *dkw, i
        return config_detach(sc->sc_dev, flags);
 }
 
-static int
-dkwedge_cleanup_parent(struct dkwedge_softc *sc, int flags)
-{
-       struct disk *dk = &sc->sc_dk;
-       int rc;
-
-       rc = 0;
-       mutex_enter(&dk->dk_openlock);
-       if (dk->dk_openmask == 0) {
-               /* nothing to do */
-       } else if ((flags & DETACH_FORCE) == 0) {
-               rc = EBUSY;
-       }  else {
-               mutex_enter(&sc->sc_parent->dk_rawlock);
-               dklastclose(sc);
-               mutex_exit(&sc->sc_parent->dk_rawlock);
-       }
-       mutex_exit(&sc->sc_dk.dk_openlock);
-
-       return rc;
-}
-
 /*
  * dkwedge_detach:
  *
@@ -709,7 +686,8 @@ dkwedge_detach(device_t self, int flags)
        }
        if (unit == ndkwedges)
                rc = ENXIO;
-       else if ((rc = dkwedge_cleanup_parent(sc, flags)) == 0) {
+       else if ((rc = disk_begindetach(&sc->sc_dk, /*lastclose*/NULL, self,
+                   flags)) == 0) {
                /* Mark the wedge as dying. */
                sc->sc_state = DKW_STATE_DYING;
        }
@@ -742,8 +720,17 @@ dkwedge_detach(device_t self, int flags)
        vdevgone(bmaj, unit, unit, VBLK);
        vdevgone(cmaj, unit, unit, VCHR);
 
-       /* Clean up the parent. */
-       dkwedge_cleanup_parent(sc, flags | DETACH_FORCE);
+       /*
+        * At this point, all block device opens have been closed,
+        * synchronously flushing any buffered writes; and all
+        * character device I/O operations have completed
+        * synchronously, and character device opens have been closed.
+        *
+        * So there can be no more opens or queued buffers by now.
+        */
+       KASSERT(sc->sc_dk.dk_openmask == 0);
+       KASSERT(bufq_peek(sc->sc_bufq) == NULL);
+       bufq_drain(sc->sc_bufq);
 
        /* Announce our departure. */
        aprint_normal("%s at %s (%s) deleted\n", device_xname(sc->sc_dev),