Messages in this thread | | | Subject | Re: missing mnt_drop_write() on open error | From | Dave Hansen <> | Date | Wed, 26 Sep 2007 09:14:32 -0700 |
| |
On Wed, 2007-09-26 at 10:38 +0200, Miklos Szeredi wrote: > > On Wed, 2007-09-26 at 01:14 +0200, Miklos Szeredi wrote: > > > I get this at umount, if there was a failed open(): > > > > > > WARNING: at fs/namespace.c:586 __mntput() > > > > > > I think the problem is that may_open() calls mnt_want_write(), but if > > > open doesn't succeed, mnt_drop_write() will not be called. > > > > Does this help? > > It didn't fix it for me, but the patch looks OK. > > In __dentry_open() there's still a few places where fput() won't be > called, notably when ->open fails, which is what I'm triggering I > think. > > Also even more horrible things can happen because of the > nd->intent.open.file thing. For example if the lookup routine calls > lookup_instantiate_filp(), and after this, but before may_open() some > error happens, then release_open_intent() will call fput() on the > file, which will cause mnt_drop_write() to be called, even though a > matching mnt_want_write() hasn't yet been called. Ugly, eh?
I used to have a patch that didn't completely trust that all files with FMODE_WRITE set to have taken a write on the mnt. I think I used a flag to indicate whether or not a particular file had a mnt_want_write() done on its behalf. It somewhat artificially keeps the mnt write count balanced, but I think it will let us detect when things like this go on.
> > I'm also thinking that we should change the open_namei* > > functions to simply return 'struct file *'. Those are the only users > > other than NFS, and forcing the return of a file like that will force > > users to do the fput() on it if they don't want it any more. We'd just > > need to make sure no new may_open() users pop up. Any thoughts on that? > > Yeah, something needs to be done with open, because currently it's way > too convoluted.
Sounds like Christoph has some ideas...
-- Dave
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |