Re: [PATCH v3 kvm/queue 03/16] mm/memfd: Introduce MEMFD_OPS

[Chao Peng]

On Fri, Dec 24, 2021 at 11:53:15AM +0800, Robert Hoo wrote:
> On Thu, 2021-12-23 at 20:29 +0800, Chao Peng wrote:
> > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> >  
> > +static void notify_fallocate(struct inode *inode, pgoff_t start,
> > pgoff_t end)
> > +{
> > +#ifdef CONFIG_MEMFD_OPS
> > +	struct shmem_inode_info *info = SHMEM_I(inode);
> > +	const struct memfd_falloc_notifier *notifier;
> > +	void *owner;
> > +	bool ret;
> > +
> > +	if (!info->falloc_notifier)
> > +		return;
> > +
> > +	spin_lock(&info->lock);
> > +	notifier = info->falloc_notifier;
> > +	if (!notifier) {
> > +		spin_unlock(&info->lock);
> > +		return;
> > +	}
> > +
> > +	owner = info->owner;
> > +	ret = notifier->get_owner(owner);
> > +	spin_unlock(&info->lock);
> > +	if (!ret)
> > +		return;
> > +
> > +	notifier->fallocate(inode, owner, start, end);
> 
> I see notifier->fallocate(), i.e. memfd_fallocate(), discards
> kvm_memfd_fallocate_range()'s return value. Should it be checked?

I think we can ignore it, just like how current mmu_notifier does,
the return value of __kvm_handle_hva_range is discarded in
kvm_mmu_notifier_invalidate_range_start(). Even when KVM side failed,
it's not fatal, it should not block the operation in the primary MMU.

Thanks,
Chao
> 
> > +	notifier->put_owner(owner);
> > +#endif
> > +}
> > +