unpin_user_page(9)

💅 unpin_user_page — the kernel API manual, bestie edition 💅

okay so real talk, this page lives in the Kernel API Manual (that's the 9 in unpin_user_page(9), iykyk) and it's about letting go of a page you dma-pinned. yes it's a one-function page. yes it still ate. let's go 🫶

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✨ NAME ✨

unpin_user_page — release a dma-pinned page 🌸

like, you held it, you pinned it, now you're releasing it. closure. main character energy.

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✨ SYNOPSIS ✨

void unpin_user_page (struct page *page );

that's it. that's the whole vibe. void return, one argument, no drama 💅

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✨ ARGUMENTS ✨

• page — pointer to the page you're releasing 🎀 literally just a pointer to the page to be released. hand it over and let it go.

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✨ DESCRIPTION ✨

okay so this is the important part, bestie, don't skip it 🙈

Pages that were pinned via pin_user_pages*() must be released via either unpin_user_page, or one of the unpin_user_pages*() routines. that's not a suggestion, that's the way it is, fr fr.

and why, you ask? because this is how such pages can be separately tracked and uniquely handled ✨ the pinning system keeps receipts so it knows exactly which pages are special. no cap.

in particular, interactions with RDMA and filesystems need special handling 👑 so yeah, these pages aren't just any pages — they have commitments. use the right unpin routine or the tracking gets messy, and we do not want the tracking to get messy.

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✨ SEE ALSO ✨

the whole friend group 💖 these are all the related pages, Kernel file ./mm/gup.c and:

• try_grab_folio(9)
• unpin_folio(9)
• folio_add_pin(9)
• unpin_user_pages_dirty_lock(9)
• unpin_user_page_range_dirty_lock(9)
• unpin_user_pages(9)
• unpin_user_folio(9)
• unpin_folios(9)
• try_grab_folio_fast(9)
• follow_page_mask(9)
• __get_user_pages(9)
• fixup_user_fault(9)
• populate_vma_page_range(9)
• fault_in_writeable(9)
• fault_in_subpage_writeable(9)
• fault_in_readable(9)
• get_dump_page(9)
• get_user_pages_remote(9)
• get_user_pages(9)
• get_user_pages_fast_only(9)
• get_user_pages_fast(9)
• pin_user_pages_fast(9)
• pin_user_pages_remote(9)
• pin_user_pages(9)
• memfd_pin_folios(9)
• folio_add_pins(9)

like. that's the entire gc. go read them, they're all iconic 🦋

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and that's the page!! 💜 source/version situation: this one's from ./mm, dated October 2026, and it's unpin_user_page(9) — mwah, periodt 💅✨🎀