Re: [PATCH v3 29/30] luo: allow preserving memfd

[Mike Rapoport <rppt@kernel.org>]

On Tue, Aug 26, 2025 at 01:20:19PM -0300, Jason Gunthorpe wrote:
> On Thu, Aug 07, 2025 at 01:44:35AM +0000, Pasha Tatashin wrote:
> 
> > +	/*
> > +	 * Most of the space should be taken by preserved folios. So take its
> > +	 * size, plus a page for other properties.
> > +	 */
> > +	fdt = memfd_luo_create_fdt(PAGE_ALIGN(preserved_size) + PAGE_SIZE);
> > +	if (!fdt) {
> > +		err = -ENOMEM;
> > +		goto err_unpin;
> > +	}
> 
> This doesn't seem to have any versioning scheme, it really should..
> 
> > +	err = fdt_property_placeholder(fdt, "folios", preserved_size,
> > +				       (void **)&preserved_folios);
> > +	if (err) {
> > +		pr_err("Failed to reserve folios property in FDT: %s\n",
> > +		       fdt_strerror(err));
> > +		err = -ENOMEM;
> > +		goto err_free_fdt;
> > +	}
> 
> Yuk.
> 
> This really wants some luo helper
> 
> 'luo alloc array'
> 'luo restore array'
> 'luo free array'

We can just add kho_{preserve,restore}_vmalloc(). I've drafted it here:
https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=kho/vmalloc/v1

Will wait for kbuild and then send proper patches.
 

-- 
Sincerely yours,
Mike.