Re: [PATCH 1/2] rust: add initial scatterlist bindings

[Abdiel Janulgue]

On 02/06/2025 14:40, Jason Gunthorpe wrote:
> On Sat, May 31, 2025 at 09:54:20PM +0900, Alexandre Courbot wrote:
>
> > So if I understood your idea correctly, this would mean creating the
> > SGTable and mapping it in one call, eschewing the typestate entirely?
>
> Probably no need for a type state
>
> > And the `SGTable` would own the backing data, and only release it upon
> > destruction and unmapping?
>
> But I don't think you can do this, it is not allowed to pin kmalloc
> memory for instance so you have to do something as you showed to tie
> the lifetime to the kmalloc across the sgtable lifetime.

We could explicitly have the SGTable own the backing store, so the 
lifetime of the pages is connected to it? ie., we have a VVec with the 
kmalloc allocator, instead of passing a a reference to pages, one could 
have the page builder something in the likes of:

sgt.init(||
	let k = Vec::<PageSlice, Kmalloc>::new();
	k.reserve(pages, GFP_KERNEL) {
	...
	)

Anyway this probably needs the related (still WIP btw) support in: 
https://lore.kernel.org/rust-for-linux/20241119112408.779243-3-abdiel.janulgue@xxxxxxxxx/ 


/Abdiel