Re: [PATCH mm-unstable v1 1/4] mm/swap: stop using page->private on tail pages for THP_SWAP

[David Hildenbrand]

On 21.08.23 18:08, David Hildenbrand wrote:
> Let's stop using page->private on tail pages, making it possible to
> just unconditionally reuse that field in the tail pages of large folios.
>
> The remaining usage of the private field for THP_SWAP is in the THP
> splitting code (mm/huge_memory.c), that we'll handle separately later.
>
> Update the THP_SWAP documentation and sanity checks in mm_types.h and
> __split_huge_page_tail().
>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---

@Andrew, the following change on top


From 2b1fd10ef07c6d47aa9cd0ce10445ab1e1b97361 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@xxxxxxxxxx>
Date: Tue, 22 Aug 2023 19:16:55 +0200
Subject: [PATCH] fixup: mm/swap: stop using page->private on tail pages for
 THP_SWAP

Per Yoshry, use folio_page_idx(). It shouldn't make a difference for
our (THP) use case, but it's certainly cleaner.

Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 include/linux/swap.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 84fe0e94f5cd..e5cf58a1cf9e 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -344,7 +344,7 @@ static inline swp_entry_t page_swap_entry(struct page *page)
 	struct folio *folio = page_folio(page);
 	swp_entry_t entry = folio_swap_entry(folio);
 
-	entry.val += page - &folio->page;
+	entry.val += folio_page_idx(folio, page);
 	return entry;
 }
 
--
2.41.0


--
Cheers,

David / dhildenb