borrow_pbn_lock_from_pool(9)

💅 borrow_pbn_lock_from_pool(9)

okay so first things first, bestie, this whole thing lives in the Kernel API Manual (that's the manual name btw, now you know ✨). It's a kernel function page, it's giving driver-internals realness, and honestly? It's kinda iconic. Let's get into it 🎀

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✨ NAME ✨

borrow_pbn_lock_from_pool — the function that literally borrows a PBN lock out of the pool and initializes it with whatever type you hand it 🫶

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🌸 SYNOPSIS 🌸

int borrow_pbn_lock_from_pool (struct pbn_lock_pool *pool , enum
pbn_lock_type type , struct pbn_lock **lock_ptr );

that's the whole signature, copied verbatim, no notes 💅

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🦋 ARGUMENTS 🦋

• pool — the pool you're borrowing from. this is your plug, your source, your supply 😌
• type — the type you wanna initialize the lock with. you pick it, you own it.
• lock_ptr — a pointer that receives the borrowed lock. it's the little basket where your lock lands 🧺

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⭐ DESCRIPTION ⭐

so like, here's the tea: pools do not grow on demand and they do not allocate memory. Periodt. 💀 Which means if the pool is empty? This call fails. No dramatic rescue, no sneaky malloc behind your back, it just says no.

And here's the part people forget (iykyk): borrowed locks are still associated with this pool, so when you're done, you must return them to only this pool. Not some other pool. Not a vibe-adjacent pool. This one. 🙈

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🔥 RETURN 🔥

• VDO_SUCCESS — you got your lock, slay 💖
• VDO_LOCK_ERROR — the pool was empty, better luck next time 😭

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👑 SEE ALSO 👑

bestie, buckle up, this list is long and every single one of these is required reading, no cap. The kernel file is ./drivers/md/dm-vdo/physical-zone.c and the crew is:

• vdo_is_pbn_read_lock(9)
• vdo_downgrade_pbn_write_lock(9)
• vdo_claim_pbn_lock_increment(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)
• 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)

that's the whole friend group, go say hi 🫶

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quick vibe check before you go: empty pool = VDO_LOCK_ERROR, and every borrowed lock goes home to the same pool it came from. That's the rule. Don't break it. 💅

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and that's the page, bestie!! 🎀 this one ships out of ./drivers/md/dm-vdo, dated October 2026 — go off, borrow responsibly, mwah 😘🌈