unmap_mapping_folio(9)

✨ unmap_mapping_folio ✨

okay so bestie, this is a page from the Kernel API Manual and it's about one (1) folio getting yeeted out of everybody's address space 🎀 literally the "you don't have to go home but you can't stay here" of memory management 💅

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🌸 NAME 🌸

unmap_mapping_folio — unmap a single folio from processes. That's it. One folio. Unmapped. Periodt. ✨

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🦋 SYNOPSIS 🦋

void unmap_mapping_folio (struct folio *folio );

the way it just takes one argument and returns void… lowkey iconic 🫶

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💖 ARGUMENTS 💖

• folio — the locked folio that's about to be unmapped 👑 heads up though: it's locked, bestie, so don't come in here without holding that lock, iykyk 🔒

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🧚 DESCRIPTION 🧚

okay so picture this: this folio is mmaped into some userspace process somewhere, right? and unmap_mapping_folio goes and unmaps it from any userspace process that still has it mmaped. no survivors. no cap. 💀

typically — and this is the efficiency era of it all — the range of nearby pages has already been unmapped, by unmap_mapping_pages or by unmap_mapping_range. so usually the bulk of the work is done and this is just the cleanup girlie ✨

but here's the plot twist 😭 once truncation or invalidation holds the lock on a folio, it might find that the page has been remapped again. like, it came back?? rude?? and that's exactly when it reaches for unmap_mapping_folio to unmap it finally. last one out, turn off the lights 🕯️

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🌈 SEE ALSO 🌈

so many references, bestie, this page has main character energy in the cross-reference department 👑 all from the kernel file ./mm/memory.c:

• free_pgd_range(9)
• free_pgtables(9)
• __vm_normal_page(9)
• vm_normal_page(9)
• vm_normal_folio(9)
• vm_normal_page_pmd(9)
• vm_normal_folio_pmd(9)
• vm_normal_page_pud(9)
• restore_exclusive_pte(9)
• cond_install_uffd_wp_ptes(9)
• zap_vma_for_reaping(9)
• unmap_vmas(9)
• zap_vma_range_batched(9)
• zap_vma_range(9)
• zap_special_vma_range(9)
• vm_insert_pages(9)
• vm_insert_page(9)
• vm_map_pages(9)
• vm_map_pages_zero(9)
• vmf_insert_pfn_prot(9)
• vmf_insert_pfn(9)
• remap_pfn_range(9)
• vm_iomap_memory(9)
• __vmf_anon_prepare(9)
• finish_mkwrite_fault(9)
• unmap_mapping_pages(9)
• unmap_mapping_range(9)
• set_pte_range(9)
• finish_fault(9)
• mm_account_fault(9)
• follow_pfnmap_start(9)
• follow_pfnmap_end(9)
• generic_access_phys(9)
• access_remote_vm(9)
• copy_remote_vm_str(9)
• folio_zero_user(9)

like… that's a whole friend group 🫶 go read them, they're all slaying in their own way 💜

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ok and one lil sign-off 💌 this page lives in ./mm, dated October 2026, and if you ever need to find it again it's filed under unmap_mapping_folio(9). mwah, go touch some pages 🍓✨