On Tue, Aug 6, 2024 at 9:30 PM Boqun Feng <boqun.feng@xxxxxxxxx> wrote:
>
> On Tue, Aug 06, 2024 at 10:48:11AM +0200, Alice Ryhl wrote:
> [...]
> > > > + /// Returns the flags associated with the file.
> > > > + ///
> > > > + /// The flags are a combination of the constants in [`flags`].
> > > > + #[inline]
> > > > + pub fn flags(&self) -> u32 {
> > > > + // This `read_volatile` is intended to correspond to a READ_ONCE call.
> > > > + //
> > > > + // SAFETY: The file is valid because the shared reference guarantees a nonzero refcount.
> > > > + //
> > > > + // FIXME(read_once): Replace with `read_once` when available on the Rust side.
> > >
> > > Do you know the status of this?
> >
> > It's still unavailable.
> >
>
> I think with our own Atomic API, we can just use atomic_read() here:
> yes, I know that to make this is not a UB, we need the C side to also do
> atomic write on this `f_flags`, however, my reading of C code seems to
> suggest that FS relies on writes to this field is atomic, therefore
> unless someone is willing to convert all writes to `f_flags` in C into
> a WRITE_ONCE(), nothing more we can do on Rust side. So using
> atomic_read() is the correct thing to begin with.
Huh? The C side uses atomic reads for this?
Alice
