On Wed, Jun 21, 2006 at 09:45:36PM +0900, YAMAMOTO Takashi wrote:
> > > for example,
> > > 
> > > int
> > > vn_remove(const char *path)
> > > {
> > > 
> > > 	lookup_parent(..., &dvp, ...);
> > > 
> > > 	vngate_enter(dvp->v_mount);
> > > 	lock(dvp);
> > > 	lookup_lastcomponent(dvp, &vp, ..);
> > > 	VOP_REMOVE(dvp, vp, ...);
> > > 	vngate_leave(dvp->v_mount);
> > > }
> > 
> > Why do you think "lookup_parent()" does not change file system data/metadata?
> 
> lookup_parent does its own vngate_enter/leave dance.
> 
> each path components can belong to different filesystems than dvp
> and i want to avoid to do vngate_enter multiple filesystems simultaneously.
> 
> > What if we make lookup() gate-aware?
> > 
> > 	- add struct mount *ni_gate, *ni_dgate to struct nameidata
> > 	- add an option KEEPGATES to namei() so namei() either leaves
> > 	  the gates on return or keeps them if KEEPGATES is given.
> 
> i hesitate to complicate namei, which is already too complex...
> 
> besides, it's desirable to have enter/leave in the same function
> if possible, IMO.  if we take the route, it's better to hide vngate_leave
> into, say, namei_done().
> 
> > and this becomes
> > 
> > 	NDINIT(..., KEEPGATES, ...)
> > 	namei(&nd);
> > 	VOP_LEASE(...)
> > 	...
> > 	VOP_REMOVE(nd.ni_dvp, nd.ni_vp, ...);
> > 	vngate_leave(nd.ni_dvp->v_mount);
> > 	vngate_leave(nd.ni_vp->v_mount);
> 
> i think it's better not to take the gate multiple times.

Ok, is it sufficient to track nd.ni_dvp in lookup() and move to nd.ni_vp if
it has a different mount (this is namei() on a mount point, should be the only
case where  nd.ni_vp->v_mount != nd.ni_dvp->v_mount)?

-- 
Juergen Hannken-Illjes - hannken@eis.cs.tu-bs.de - TU Braunschweig (Germany)