On Thu, Jun 29, 2023 at 08:45:39PM -0700, Suren Baghdasaryan wrote:
> On Thu, Jun 29, 2023 at 8:36 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> >
> > On Thu, Jun 29, 2023 at 07:04:33PM -0700, Suren Baghdasaryan wrote:
> > > Change folio_lock_or_retry to accept vm_fault struct and return the
> > > vm_fault_t directly.
> >
> > I thought we decided to call this folio_lock_fault()?
> >
> > > +static inline vm_fault_t folio_lock_or_retry(struct folio *folio,
> > > + struct vm_fault *vmf)
> > > {
> > > might_sleep();
> > > - return folio_trylock(folio) || __folio_lock_or_retry(folio, mm, flags);
> > > + return folio_trylock(folio) ? 0 : __folio_lock_or_retry(folio, vmf);
> >
> > No, don't use the awful ternary operator. The || form is used
> > everywhere else.
>
> Ok, but folio_trylock() returns a boolean while folio_lock_or_retry
> should return vm_fault_t. How exactly do you suggest changing this?
> Something like this perhaps:
>
> static inline vm_fault_t folio_lock_or_retry(struct folio *folio,
> struct vm_fault *vmf)
> {
> might_sleep();
> if (folio_trylock(folio))
> return 0;
> return __folio_lock_or_retry(folio, mm, flags);
> }
>
> ?
I think the automatic casting would work, but I prefer what you've
written here.
> > > /*
> > > * Return values:
> > > - * true - folio is locked; mmap_lock is still held.
> > > - * false - folio is not locked.
> > > + * 0 - folio is locked.
> > > + * VM_FAULT_RETRY - folio is not locked.
> >
> > I don't think we want to be so prescriptive here. It returns non-zero
> > if the folio is not locked. The precise value is not something that
> > callers should depend on.
>
> Ok, I'll change it to "non-zero" here.
Thanks!
