Re: [PATCH v3 3/3] VFS: add vfs_lookup_open() for nfsd

[Jori Koolstra <jkoolstra@xs4all.nl>]

> Op 15-07-2026 00:58 CEST schreef NeilBrown <neilb@ownmail.net>:
> 
> > 
> > Yes, sounds good. Keep in mind that vfs_open() does not handle truncate, it only
> > happens in do_open() in the open(2) path, so you must handle the actual truncation
> > back in the nfsd code. You are probably very aware of this, but just in case :)
> 
> O_TRUNC handling is a bit untidy (or convoluted to use your word).  Some
> atomic_open functions implement it, some deliberately don't.  If
> atomic_open wasn't used, it happens much later.  Maybe I could try and
> tidy that up.
> 

Wait, so for those ->atomic_open() filesystems that do handle truncate, how do
they deal with this? In do_open() we have

	if (file->f_mode & FMODE_CREATED) {
		/* Don't check for write permission, don't truncate */
		open_flag &= ~O_TRUNC;
		acc_mode = 0;
	} else if (d_is_reg(nd->path.dentry) && open_flag & O_TRUNC) {
                ...
		do_truncate = true;
	}

So on truncate do they just set FMODE_CREATED regardless of whether the file existed
before or not? Or does truncate count as create in general?

> > 
> > __O_REGULAR is also only handled in do_open(), so it does nothing in namei.c right
> > now, still seems good to include it. I don't understand why the __O_REGULAR
> > implementation is so convoluted, but I haven't looked into it yet. I plan to do
> > that sometime soon.
> 
> Some atomic_open functions handle __O_REGULAR, and I think it best to
> abort an unwanted open as early as possible.

Yes, you are right, my bad.

> "convoluted" happens when code grows over time and people work with what
> is there rather than tidying it up first, then working with tidy code.
> We cannot tidy everything all at once, but if everyone making changes
> does a little bit of tidying, we might avoid too much convolution!
> 

Haha, maybe this is math-speak, just like you have legalese. My professor at
McGill used to call certain proofs "convoluted" if they involved a lot of
seemingly senseless rigmarole. I guess the term stuck :)

Best,
Jori.