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Previous did cause a deadlock with layered FS: the vrele thread 

can sleep on the vnode lock, while vget is sleeping on the
VI_INACTNOW flag (or the vget caller is looping on vget returning failure
because of the VI_INACTNOW flag). With layered FSes, the upper and lower
vnodes share the same lock, so the vget() caller above can be already
holding the vnode lock.

Fix by dropping VI_INACTNOW before sleeping on the vnode lock in
vrelel(), and check the ref count again once we have the lock. If the
vnode has more than one reference, donc VOP_INACTIVE it.
Fix PR kern/42318 and PR kern/42377
patch tested by Hisashi T Fujinaka, Joachim König, Stephen Borrill and
Matthias Scheler.
This commit is contained in:
bouyer 2009-11-28 10:10:17 +00:00
parent c6e1f64d7a
commit 8c392da154
1 changed files with 20 additions and 4 deletions
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24
sys/kern/vfs_subr.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: vfs_subr.c,v 1.391 2009/11/27 16:43:51 pooka Exp $ */
/* $NetBSD: vfs_subr.c,v 1.392 2009/11/28 10:10:17 bouyer Exp $ */
/*-
* Copyright (c) 1997, 1998, 2004, 2005, 2007, 2008 The NetBSD Foundation, Inc.
@ -91,7 +91,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_subr.c,v 1.391 2009/11/27 16:43:51 pooka Exp $");
__KERNEL_RCSID(0, "$NetBSD: vfs_subr.c,v 1.392 2009/11/28 10:10:17 bouyer Exp $");
#include "opt_ddb.h"
#include "opt_compat_netbsd.h"
@ -1429,14 +1429,30 @@ vrelel(vnode_t *vp, int flags)
/* The pagedaemon can't wait around; defer. */
defer = true;
} else if (curlwp == vrele_lwp) {
/* We have to try harder. */
vp->v_iflag &= ~VI_INACTREDO;
/*
* We have to try harder. But we can't sleep
* with VI_INACTNOW as vget() may be waiting on it.
*/
vp->v_iflag &= ~(VI_INACTREDO|VI_INACTNOW);
cv_broadcast(&vp->v_cv);
error = vn_lock(vp, LK_EXCLUSIVE | LK_INTERLOCK |
LK_RETRY);
if (error != 0) {
/* XXX */
vpanic(vp, "vrele: unable to lock %p");
}
mutex_enter(&vp->v_interlock);
/*
* if we did get another reference while
* sleeping, don't try to inactivate it yet.
*/
if (__predict_false(vtryrele(vp))) {
VOP_UNLOCK(vp, 0);
mutex_exit(&vp->v_interlock);
return;
}
vp->v_iflag |= VI_INACTNOW;
mutex_exit(&vp->v_interlock);
defer = false;
} else if ((vp->v_iflag & VI_LAYER) != 0) {
/*