Messages in this thread | | | Date | Wed, 19 Mar 2008 18:20:05 +0000 | From | Al Viro <> | Subject | Re: [patch 3/6] vfs: mountinfo stable peer group id |
| |
On Wed, Mar 19, 2008 at 05:41:15PM +0100, Miklos Szeredi wrote: > > > From: Miklos Szeredi <mszeredi@suse.cz> > > Um? Do you ever need to take it outside of vfsmount_lock? > > > > Tried to think this through: > > It's always called with namespace_sem, which is enough, no need for a > new lock. The bigger problem, is that it _is_ called with > vfsmount_lock in one case, which is bad, since the allocation may > sleep.
It is called with vfsmount_lock in *all* cases. You've missed one in umount_tree(), BTW; you won't block in that case, though.
> That is in do_change_type(). But do we really need to hold > vfsmount_lock in that case?
Not the issue.
> I think not, the propagation tree has no > relevance outside namespace_sem, so that one should be sufficient.
Callers manipulate more than propagation tree. Note that e.g. umount_tree() changes all sorts of data structures, including ones that are traversed without namespace_sem.
I _really_ don't like the idea of different locking rules for caller of a function depending on the value of argument of that function. They are complicated enough as it is.
Argh... OK, I'll try to put something together tonight, after I get some sleep - 31 hours of uptime _suck_ ;-/ BTW, on top of everything else, the current variant plays interesting games with CL_PROPAGATION behaviour and I really don't like the look of what it's doing there. Later...
| |