folio_referenced(9)

🌸 folio_referenced(9) — the kernel API manual, bestie edition 🌸

okay so this is folio_referenced(9) from the Kernel API Manual, and it's honestly such a little icon. it answers one very specific question: was this folio, like, touched? 👀 let's get into it.

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✨ NAME ✨

folio_referenced — test if the folio was referenced. that's it. that's the whole vibe check. 🫶

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🎀 SYNOPSIS 🎀

int folio_referenced (struct folio *folio , int is_locked , struct
mem_cgroup *memcg , vma_flags_t *vma_flags );

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💅 ARGUMENTS 💅

• folio — the folio you're testing, bestie. the main character of this whole operation. 👑
• is_locked — says whether the caller holds the lock on the folio. caller-held lock energy.
• memcg — the target memory cgroup.
• vma_flags — a combination of all the vma->flags which referenced the folio. like a little receipt of who came by 💖

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🦋 DESCRIPTION 🦋

quick test_and_clear_referenced for all mappings of a folio. lowkey a speedy little check across every mapping, ngl. ⭐

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🧚 RETURN 🧚

it gives you back the number of mappings which referenced the folio. 🔥

but heads up: it returns -1 if the function bailed out due to rmap lock contention 😭 — that's contention, not "no refs", so don't get it twisted.

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🌈 SEE ALSO 🌈

so many siblings, fr fr. all of these live in the kernel file ./mm/rmap.c:

• __anon_vma_prepare(9)
• anon_vma_clone(9)
• unlink_anon_vmas(9)
• page_address_in_vma(9)
• mapping_wrprotect_range(9)
• pfn_mkclean_range(9)
• folio_move_anon_rmap(9)
• __folio_set_anon(9)
• __page_check_anon_rmap(9)
• folio_add_anon_rmap_ptes(9)
• folio_add_anon_rmap_pmd(9)
• folio_add_new_anon_rmap(9)
• folio_add_file_rmap_ptes(9)
• folio_add_file_rmap_pmd(9)
• folio_add_file_rmap_pud(9)
• folio_remove_rmap_ptes(9)
• folio_remove_rmap_pmd(9)
• folio_remove_rmap_pud(9)
• try_to_unmap(9)
• try_to_migrate(9)
• make_device_exclusive(9)
• __rmap_walk_file(9)

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anyway that's the whole page, no notes 💜 this one came to you from ./mm, dated October 2026 — mwah, go check your folios, ily, bye!! 🎀✨