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

[Abdiel Janulgue <abdiel.janulgue@gmail.com>]

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@gmail.com/ 


/Abdiel