On Tue, 25 May 2010 02:58:22 +0100 Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Tue, May 25, 2010 at 11:14:05AM +1000, Neil Brown wrote: > > > I must confess though that I don't feel I understand VFS name lookup properly > > any more. Since intents were added it seems to have become much more obscure > > and complex. I cannot help thinking that there must be a better way: > > distinguish between the various cases at a higher level so we don't need as > > many flags being passed around and interpreted by widely separate pieces of > > code. I don't have a concrete proposal but I would certainly be interested > > to work on one if there were any hope of real change. > > Thoughts? > > Intents are vile crap that has been introduced by the nfs folks to start > with... I've been trying to localize the mess and it's got a _lot_ better > than it used to be a year ago, but they are still not gone. And yes, I > plan to kill that crap. Basically, most of the do_last() guts will become > a method that would get struct file *explicitly* and ask the fs to do > (possibly atomic) open. With normal filesystems defaulting to what's there > right now. That sounds like the sort of direction I was imagining. I note however that vfat uses intents in a way that would not be addressed by a '->do_last' method. It wants to invalidate negative dentries in d_revalidate if they are the target of a rename (or another create), and presumably rename wouldn't use ->do_last? Or maybe it would, but with a NULL file ?? > > The main obstacle at the moment is in ->d_revalidate() abuses. NFS, CIFS > *and* autofs, the last one in a way that isn't really compatible with what > NFS et.al. are trying to do. Overloading of ->d_revalidate() and ->lookup() > to do the work of open() doesn't help, and the horrors nfs4 piles on top > of that are even scarier. > > _Another_ fine piece of something is ->follow_link() abuses, including > referrals' treatment. Also tied to the previous messes. > > We definitely will need to get VFS-to-fs APIs in that area changed; most of > the mess has been created by the deeply misguided efforts to keep the API > changes minimal. > > As for the flags, quite a few will be gone once we split "opening the final > component" from the normal cases. Google for lookup_instantiate_filp+shit > for details of these plans... I tried cloning git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6.git and couldn't find anything in the 'untested' branch. Did I look in the wrong place? Is there some work-in-progress I can explore? Thanks, NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
