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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.
This commit is contained in:
riastradh 2023-04-21 18:30:52 +00:00
parent 385414544c
commit 932706d0fa
1 changed files with 15 additions and 28 deletions
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43
sys/dev/dkwedge/dk.c
View File

@ -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, int flags)
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),