vdo_claim_pb...ck_increment(9)

💅 vdo_claim_pb...ck_increment(9)

okay so real talk, this is a page straight out of the Kernel API Manual and it's genuinely so niche and so specific and I'm obsessed 🎀 like it's one tiny function doing one tiny job in dm-vdo and honestly? iconic.

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✨ NAME ✨

vdo_claim_pbn_lock_increment — bestie, this is the one that tries to claim one of the available reference count increments on a read lock. that's it, that's the whole vibe 🦋

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🌸 SYNOPSIS 🌸

bool vdo_claim_pbn_lock_increment (struct pbn_lock *lock );

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🫶 ARGUMENTS 🫶

• lock — the PBN read lock you're trying to claim an increment from. that's your girl, that's the one 💜

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💖 DESCRIPTION 💖

so here's the tea: claims can be attempted from any thread. any thread!! no cap 🧚

but — and this is the important part, do not skip this — a claim is only valid until the PBN lock is released. after that it's giving expired, it's giving stale, it's giving nothing 😭 so like, use it while you've got it, yk?

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🔥 RETURN 🔥

true if the claim succeeded — which guarantees that one increment can be made without overflowing the PBN's reference count. slay, no overflow, we love a safe increment ✨

ngl there is no "false" description here, the page only documents the true case. i'm not making stuff up, i'm just the messenger 💅

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👑 SEE ALSO 👑

kernel file ./drivers/md/dm-vdo/physical-zone.c, plus the whole friend group:

• vdo_is_pbn_read_lock(9)
• vdo_downgrade_pbn_write_lock(9)
• vdo_assign_pbn_lock_provisional_reference(9)
• vdo_unassign_pbn_lock_provisional_reference(9)
• release_pbn_lock_provisional_reference(9)
• union idle_pbn_lock(9)
• struct pbn_lock_pool(9)
• return_pbn_lock_to_pool(9)
• make_pbn_lock_pool(9)
• free_pbn_lock_pool(9)
• borrow_pbn_lock_from_pool(9)
• initialize_zone(9)
• vdo_make_physical_zones(9)
• vdo_free_physical_zones(9)
• vdo_get_physical_zone_pbn_lock(9)
• vdo_attempt_physical_zone_pbn_lock(9)
• allocate_and_lock_block(9)
• retry_allocation(9)
• continue_allocating(9)
• vdo_allocate_block_in_zone(9)
• vdo_release_physical_zone_pbn_lock(9)
• vdo_dump_physical_zone(9)

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and that's the whole page bestie, mwah 💋 this one lives in ./drivers/md/dm-vdo and it's dated October 2026 — go read the source, it ate fr fr 🍓💅