folio_page_idx(9)

💅 folio_page_idx(9) — Kernel API Manual bestie edition ✨

Hii bestie! You're in the Kernel API Manual, and today's main character is folio_page_idx(9). It's a tiny little number-fetcher, but honestly? Iconic. 🎀

🌸 NAME 🌸

folio_page_idx — gives you the number of a page in a folio. Literally that's the whole job, and it ate. 💖

✨ SYNOPSIS ✨

unsigned long folio_page_idx (const struct folio *folio , const struct page *page );

🎀 ARGUMENTS 🎀

• folio — the folio. Your group project's main character. 👑
• page — the folio page. The specific page bestie we're locating inside the folio. 🦋

🦋 DESCRIPTION 🦋

OK so listen: this function expects that page is actually part of folio. No random stray page sneaking in like it's a plus-one, bestie. 💀

The number it returns is relative to the start of the folio. So it's an index-from-the-beginning situation, and that relative-to-start detail is lowkey important. ✨

💜 SEE ALSO 💜

The whole squad lives in Kernel file ./include/linux/mm.h: vma_flag_t(9), fault_flag_allow_retry_first(9), vma_kernel_pagesize(9), folio_order(9), folio_reset_order(9), folio_mapcount(9), folio_mapped(9), thp_order(9), thp_size(9), folio_get(9), folio_put(9), folio_put_refs(9), folios_put(9), vma_flags_is_cow_mapping(9), vma_is_cow_mapping(9), vma_desc_is_cow_mapping(9), folio_pfn(9), folio_mk_pte(9), folio_mk_pmd(9), folio_mk_pud(9), folio_maybe_dma_pinned(9), is_zero_page(9), is_zero_folio(9), folio_nr_pages(9), folio_next(9), folio_shift(9), folio_size(9), folio_maybe_mapped_shared(9), folio_expected_ref_count(9), zap_vma(9), ptdesc_address(9), ptdesc_set_kernel(9), ptdesc_clear_kernel(9), ptdesc_test_kernel(9), pagetable_alloc(9), pagetable_free(9), vma_lookup(9), vma_start_pgoff(9), vma_end_pgoff(9), vma_last_pgoff(9), vma_start_anon_pgoff(9), vma_end_anon_pgoff(9), vma_last_anon_pgoff(9), mmap_action_remap(9), mmap_action_remap_full(9), mmap_action_ioremap(9), mmap_action_ioremap_full(9), mmap_action_simple_ioremap(9), mmap_action_map_kernel_pages(9), mmap_action_map_kernel_pages_full(9), range_is_subset(9), range_in_vma(9), range_in_vma_desc(9), clear_pages(9)

Cute little sign-off: this page is from ./include/linux, dated October 2026. Go forth and index responsibly, bestie. 💅🫶🍓