[src/trunk]: src/sys/dev/dkwedge dk(4): Set .d_cfdriver and .d_devtounit to p...

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

details:   https://anonhg.NetBSD.org/src/rev/84dc29b8e1e3
branches:  trunk
changeset: 374390:84dc29b8e1e3
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Fri Apr 21 18:31:00 2023 +0000

description:
dk(4): Set .d_cfdriver and .d_devtounit to plug open/detach race.

This way, opening dkN or rdkN will wait if attach or detach is still
in progress, and vdevgone will wake up such pending opens and make
them fail.  So it is no longer possible for a wedge to be detached
after dkopen has already started using it.

For now, we use a custom .d_devtounit function that looks up the
autoconf unit number via the dkwedges array, which conceivably may
use an independent unit numbering system -- nothing guarantees they
match up.  (In practice they will mostly match up, but concurrent
wedge creation could lead to different numbering.)  Eventually this
should be changed so the two numbering systems match, which would let
us delete the new dkunit function and just use dev_minor_unit like
many other drivers can.

diffstat:

 sys/dev/dkwedge/dk.c |  40 ++++++++++++++++++++++++++++++++++++++--
 1 files changed, 38 insertions(+), 2 deletions(-)

diffs (82 lines):

diff -r 3f5966c489d1 -r 84dc29b8e1e3 sys/dev/dkwedge/dk.c
--- a/sys/dev/dkwedge/dk.c      Fri Apr 21 18:30:52 2023 +0000
+++ b/sys/dev/dkwedge/dk.c      Fri Apr 21 18:31:00 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: dk.c,v 1.143 2023/04/21 18:30:52 riastradh Exp $       */
+/*     $NetBSD: dk.c,v 1.144 2023/04/21 18:31:00 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 1.143 2023/04/21 18:30:52 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: dk.c,v 1.144 2023/04/21 18:31:00 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_dkwedge.h"
@@ -114,6 +114,8 @@ static int  dkwedge_del1(struct dkwedge_i
 static int     dk_open_parent(dev_t, int, struct vnode **);
 static int     dk_close_parent(struct vnode *, int);
 
+static int     dkunit(dev_t);
+
 static dev_type_open(dkopen);
 static dev_type_close(dkclose);
 static dev_type_cancel(dkcancel);
@@ -139,6 +141,8 @@ const struct bdevsw dk_bdevsw = {
        .d_dump = dkdump,
        .d_psize = dksize,
        .d_discard = dkdiscard,
+       .d_cfdriver = &dk_cd,
+       .d_devtounit = dkunit,
        .d_flag = D_DISK | D_MPSAFE
 };
 
@@ -155,6 +159,8 @@ const struct cdevsw dk_cdevsw = {
        .d_mmap = nommap,
        .d_kqfilter = nokqfilter,
        .d_discard = dkdiscard,
+       .d_cfdriver = &dk_cd,
+       .d_devtounit = dkunit,
        .d_flag = D_DISK | D_MPSAFE
 };
 
@@ -1217,6 +1223,36 @@ dk_close_parent(struct vnode *vp, int mo
 }
 
 /*
+ * dkunit:             [devsw entry point]
+ *
+ *     Return the autoconf device_t unit number of a wedge by its
+ *     devsw dev_t number, or -1 if there is none.
+ *
+ *     XXX This is a temporary hack until dkwedge numbering is made to
+ *     correspond 1:1 to autoconf device numbering.
+ */
+static int
+dkunit(dev_t dev)
+{
+       int mn = minor(dev);
+       struct dkwedge_softc *sc;
+       device_t dv;
+       int unit = -1;
+
+       if (mn < 0)
+               return -1;
+
+       rw_enter(&dkwedges_lock, RW_READER);
+       if (mn < ndkwedges &&
+           (sc = dkwedges[minor(dev)]) != NULL &&
+           (dv = sc->sc_dev) != NULL)
+               unit = device_unit(dv);
+       rw_exit(&dkwedges_lock);
+
+       return unit;
+}
+
+/*
  * dkopen:             [devsw entry point]
  *
  *     Open a wedge.