Date: Sun, 23 Nov 2003 15:57:01 -0800 (PST) From: Don Lewis <truckman@FreeBSD.org> To: current@FreeBSD.org Subject: null_lookup() vnode locking wierdness Message-ID: <200311232357.hANNv1eF006528@gw.catspoiler.org>
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I was trying to figure out why the VOP_UNLOCK() call in null_lookup()
was violating a vnode locking assertion, so I tossed a bunch of
ASSERT_VOP_LOCKED() calls into null_lookup(). I found something I don't
understand ...
ASSERT_VOP_LOCKED(dvp, "null_lookup 1");
if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
return (EROFS);
/*
* Although it is possible to call null_bypass(), we'll do
* a direct call to reduce overhead
*/
ASSERT_VOP_LOCKED(dvp, "null_lookup 2");
ldvp = NULLVPTOLOWERVP(dvp);
ASSERT_VOP_LOCKED(dvp, "null_lookup 3");
vp = lvp = NULL;
error = VOP_LOOKUP(ldvp, &lvp, cnp);
ASSERT_VOP_LOCKED(dvp, "null_lookup 4");
if (error == EJUSTRETURN && (flags & ISLASTCN) &&
(dvp->v_mount->mnt_flag & MNT_RDONLY) &&
(cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME))
error = EROFS;
/*
* Rely only on the PDIRUNLOCK flag which should be carefully
* tracked by underlying filesystem.
*/
if (cnp->cn_flags & PDIRUNLOCK)
VOP_UNLOCK(dvp, LK_THISLAYER, td);
The null_lookup {1,2,3} assertions pass, but null_lookup 4 fails. It
appears that the VOP_LOOKUP() call to the underlying file system is
unlocking the directory vnode in the nullfs file system. How can that
happen?
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