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Rework ".." lookup; previous one failed to properly busy the mountpoint.

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Reviewed by:	kib@
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
trasz 2014-08-20 13:46:51 +00:00
parent 42a486f3a8
commit 90fa877deb
1 changed files with 18 additions and 14 deletions
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32
sys/fs/autofs/autofs_vnops.c
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@ -197,6 +197,15 @@ autofs_trigger_vn(struct vnode *vp, const char *path, int pathlen,
return (0);
}
static int
autofs_vget_callback(struct mount *mp, void *arg, int lkflags __unused,
struct vnode **vpp)
{
return (autofs_node_vn(arg, mp, vpp));
}
static int
autofs_lookup(struct vop_lookup_args *ap)
{
@ -217,24 +226,19 @@ autofs_lookup(struct vop_lookup_args *ap)
if (cnp->cn_flags & ISDOTDOT) {
KASSERT(anp->an_parent != NULL, ("NULL parent"));
/*
* Note that in this case, dvp is the child vnode, and we are
* looking up the parent vnode - exactly reverse from normal
* operation. To preserve lock order, we unlock the child
* (dvp), obtain the lock on parent (*vpp) in autofs_node_vn(),
* then relock the child. We use vhold()/vdrop() to prevent
* dvp from being freed in the meantime.
* Note that in this case, dvp is the child vnode, and we
* are looking up the parent vnode - exactly reverse from
* normal operation. Unlocking dvp requires some rather
* tricky unlock/relock dance to prevent mp from being freed;
* use vn_vget_ino_gen() which takes care of all that.
*/
lock_flags = VOP_ISLOCKED(dvp);
vhold(dvp);
VOP_UNLOCK(dvp, 0);
error = autofs_node_vn(anp->an_parent, mp, vpp);
error = vn_vget_ino_gen(dvp, autofs_vget_callback,
anp->an_parent, 0, vpp);
if (error != 0) {
AUTOFS_WARN("autofs_node_vn() failed with error %d",
AUTOFS_WARN("vn_vget_ino_gen() failed with error %d",
error);
return (error);
}
vn_lock(dvp, lock_flags | LK_RETRY);
vdrop(dvp);
return (error);
}