[PATCH 1/8] mm/swap: add folio_swap_entry() and folio_page_swap_entry()
From: Tal Zussman <hidden>
Date: 2026-08-30 10:33:50
Also in:
linux-mm, lkml
Subsystem:
memory management - swap, the rest · Maintainers:
Andrew Morton, Chris Li, Kairui Song, Linus Torvalds
A folio in the swap cache occupies folio_nr_pages() contiguous swap entries starting at folio->swap, so a page's swap entry is just folio->swap plus the page's index in the folio. page_swap_entry() hides this behind a compound_head() call, and callers that already have the folio sometimes open-code the arithmetic instead. Add folio_swap_entry(), which takes a folio and a page index, and folio_page_swap_entry() for callers that have the page. Signed-off-by: Tal Zussman <redacted> --- include/linux/swap.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 0f953ed9c863..48632aacbc2a 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h@@ -278,6 +278,39 @@ struct swap_info_struct { const struct swap_ops *ops; }; +/** + * folio_swap_entry - Return the swap entry for a page within a folio. + * @folio: The folio. + * @idx: The index of the page within the folio. + * + * A folio in the swap cache occupies folio_nr_pages() contiguous swap + * entries starting at folio->swap. The caller must ensure the folio is + * in the swap cache and that @idx is within the folio. + */ +static inline +swp_entry_t folio_swap_entry(const struct folio *folio, unsigned long idx) +{ + swp_entry_t entry = folio->swap; + + VM_WARN_ON_ONCE_FOLIO(idx >= folio_nr_pages(folio), folio); + entry.val += idx; + return entry; +} + +/** + * folio_page_swap_entry - Return the swap entry of a page in a folio. + * @folio: The folio containing @page. + * @page: A page within @folio. + * + * The caller must ensure the folio is in the swap cache and that @page + * is part of @folio. + */ +static inline swp_entry_t folio_page_swap_entry(const struct folio *folio, + const struct page *page) +{ + return folio_swap_entry(folio, folio_page_idx(folio, page)); +} + static inline swp_entry_t page_swap_entry(struct page *page) { struct folio *folio = page_folio(page);
--
2.39.5