folio_maybe_dma_pinned(9)

✨ NAME ✨

okay so bestie, welcome to folio_maybe_dma_pinned(9) from the Kernel API Manual 💖 — the whole vibe is: Report if a folio may be pinned for DMA. No cap, that’s the name energy.

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📜 SYNOPSIS 📜

bool folio_maybe_dma_pinned (struct folio *folio );

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🫶 ARGUMENTS 🫶

• folio — The folio. literally the folio, that’s the arg 🎀

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💫 DESCRIPTION 💫

This function checks if a folio has been pinned via a call to a function in the pin_user_pages family. yep, that’s the whole quest 💅

For small folios, the return value is partially fuzzy: false is not fuzzy, because it means “definitely not pinned for DMA”, but true means “probably pinned for DMA, but possibly a false positive due to having at least GUP_PIN_COUNTING_BIAS worth of normal folio references”. bestie, the vibes are approximate but the words are exact 🫶

False positives are OK, because:

• a) it’s unlikely for a folio to get that many refcounts, and
• b) all the callers of this routine are expected to be able to deal gracefully with a false positive.

For most large folios, the result will be exactly correct. That’s because we have more tracking data available: the _pincount field is used instead of the GUP_PIN_COUNTING_BIAS scheme. more tracking data = main character energy ✨

For more information, please see Documentation/core-api/pin_user_pages.rst 📚

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🎀 RETURN 🎀

True, if it is likely that the folio has been “dma-pinned”. False, if the folio is definitely not dma-pinned. no fuzzy false, just fuzzy true, iykyk 💜

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🔗 SEE ALSO 🔗

Kernel file ./include/linux/mm.h is on the list too, and then the whole friend group is: folio_page_idx(9), 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), 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) 💅✨

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okay that’s the whole read, bestie 🫶 Source/version: ./include/linux · date: October 2026 · page: folio_maybe_dma_pinned(9) — mwah, go forth and vibe-check those folios 💖🎀