Date: Tue, 30 Aug 2005 15:47:04 -0700 From: Alfred Perlstein <alfred@freebsd.org> To: Alexander Kabaev <kan@FreeBSD.org> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern vfs_lookup.c Message-ID: <20050830224704.GI77060@elvis.mu.org> In-Reply-To: <200508301612.j7UGC3CM085774@repoman.freebsd.org> References: <200508301612.j7UGC3CM085774@repoman.freebsd.org>
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Ok, maybe I'm missing something, but...
while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
(cnp->cn_flags & NOCROSSMOUNT) == 0) {
KASSERT(dp != ndp->ni_dvp, ("XXX"));
if (vfs_busy(mp, 0, 0, td))
continue;
here ->>> vput(dp);
tvfslocked = VFS_LOCK_GIANT(mp);
VFS_UNLOCK_GIANT(vfslocked);
vfslocked = tvfslocked;
VOP_UNLOCK(ndp->ni_dvp, 0, td);
error = VFS_ROOT(mp, cnp->cn_lkflags, &tdp, td);
VOP_LOCK(ndp->ni_dvp, cnp->cn_lkflags | LK_RETRY, td);
vfs_unbusy(mp, td);
if (error) {
dpunlocked = 1;
goto bad2;
}
ndp->ni_vp = dp = tdp;
}
Isn't dp already unlocked here? vput should be unlocking the vnode
and we have the above KASSERT showing that they should be the same
vnode...
Also, I think lockparent doesn't need to be respected because
we're trading parent vnodes. Basically, we're hitting a vnode
that has another vnode stacked on it (root vnode), and switching to it.
we're not actually decending.
Is this OK?
-Alfred
* Alexander Kabaev <kan@FreeBSD.org> [050830 09:12] wrote:
> kan 2005-08-30 16:12:03 UTC
>
> FreeBSD src repository
>
> Modified files: (Branch: RELENG_6)
> sys/kern vfs_lookup.c
> Log:
> MFC r1.81:
> Do not keep parent directory locked while calling VFS_ROOT to
> traverse mount points in lookup(). The lock can be dropped safely
> around VFS_ROOT because LOCKPARENT semantics with child and parent
> vnodes coming from different FSes does not really have any meaningful
> use and we do not really care about parent state after we relock it.
> This prevents easily triggered deadlock on systems using automounter
> daemon.
>
> Approved by: re (scottl)
>
> Revision Changes Path
> 1.80.2.1 +2 -0 src/sys/kern/vfs_lookup.c
--
- Alfred Perlstein
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