gmap_helper_...t_pte_unused(9)

💅 gmap_helper_...t_pte_unused(9) — from the Kernel API Manual, bestie 🎀

okay so this is a whole manpage from the Kernel API Manual and it's genuinely kinda iconic — we're talking about gmap_helper_try_set_pte_unused, a little s390 helper that does exactly one thing and does it well. listen up 🫶

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✨ NAME ✨

gmap_helper_try_set_pte_unused — the way this function's whole personality is marking a pte entry as unused. that's it. that's the job. no cap 💅

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🌸 SYNOPSIS 🌸

void gmap_helper_try_set_pte_unused (struct mm_struct *mm , unsigned
long vmaddr );

like, it returns void (nothing back, she's not a gossip) and takes two args. slay ✨

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🦋 ARGUMENTS 🦋

• mm — bestie, this is the mm. the struct mm_struct *. that's the whole description, no notes 🙈
• vmaddr — the userspace address whose pte is to be marked. that's the one getting the glow-up (or rather, the un-glow-up) ⭐

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💖 DESCRIPTION 💖

so what it does is: it marks the pte corresponding to the given address as unused. and why do we care? because this makes core mm code just drop this page instead of swapping it. literally — drop it, don't swap it. bye page 👋💀

and here's the part where you gotta pay attention, bestie, because this is the vibe check that matters 👑

This function needs to be called with interrupts disabled (for example while holding a spinlock), or while holding the mmap lock. can't stress this enough 🫶

Normally this function is called as a result of an unmap operation, and thus KVM common code will already hold kvm->mmu_lock in write mode. so lowkey the locking just works out — but only because the caller set it up that way. iykyk 😌

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🔥 CONTEXT 🔥

Needs to be called while holding the mmap lock or with interrupts disabled. no exceptions, she's strict about this one 💅

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🌈 SEE ALSO 🌈

• the kernel file ./arch/s390/mm/gmap_helpers.c
• try_get_locked_pte(9)
• gmap_helper_zap_one_page(9)
• gmap_helper_discard(9)
• gmap_helper_disable_cow_sharing(9)

go read those too, they're all in the same friend group 🧚💜

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and that's the page!! it lives under ./arch/s390/mm, dated October 2026 — so like, mark your calendars bestie 🍓✨ bye!! 💖