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

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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




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