Re: [PATCH] lib/scatterlist: Fix to calculate the last_pg properly

[Yishai Hadas]

On 10/01/2023 7:08, Matthew Wilcox wrote:
> On Mon, Jan 09, 2023 at 04:47:01PM +0200, Yishai Hadas wrote:
> >   	if (sgt_append->prv) {
> > +		unsigned long paddr =
> > +			(page_to_pfn(sg_page(sgt_append->prv)) * PAGE_SIZE +
> 1. page_to_pfn() * PAGE_SIZE is spelled page_to_phys()
>
> 2. physical addresses have type phys_addr_t.  Oh, wait, paddr isn't a
> physical address, it's a pfn because you divide by PAGE_SIZE at the end.
> But you will get truncation on 32-bit, because page_to_pfn() has type
> unsigned long.  Anyway, this shouldn't be called paddr.  Maybe last_pfn
> or something?
>
> > +			 sgt_append->prv->offset + sgt_append->prv->length) /
> > +			PAGE_SIZE;

In this area of the patch I just reverted to what we had in 6.1 [1] 
where we were good.

I can send V1 and replace the 'paddr' to be called 'last_pfn' if it's 
really needed.

Alternatively, we can stay with this patch version unless you can see 
here any real issue.

What do you suggest ?

[1] https://elixir.bootlin.com/linux/v6.1.4/source/lib/scatterlist.c#L462

Yishai