decrement_for_data(9)

📦 version 7.3.1, in nixpkgs unstable

💅 decrement_for_data(9)

okay bestie, buckle up 💖 this is one of those pages from the Kernel API Manual (yes, the actual kernel API manual, we're in the big leagues now ✨), and it's all about making a data block's reference count go down. One. Just one. Iconic of it, honestly.

✨ NAME ✨

decrement_for_data — decrement the reference count for a data block. that's it, that's the whole job 🎀

🦋 SYNOPSIS 🦋

int decrement_for_data (struct vdo_slab *slab , struct reference_block
*block , slab_block_number block_number , enum reference_status
old_status , struct reference_updater *updater , vdo_refcount_t
*counter_ptr , bool adjust_block_count );

look at all those parameters, she's high-maintenance and we love that for her 💅

🌸 ARGUMENTS 🌸

okay so every single one of these matters, no skipping, i'm watching you 👀

  • slab — the slab which owns the block. like, the block lives here, this is its home 🏠
  • block — the reference block which contains the block being updated. the container of the thing, ykwim?
  • block_number — the block to update. which one we're touching, fr fr
  • old_status — the reference status of the data block before this decrement. like a "before" pic but for reference status 📸
  • updater — the reference updater doing this operation, in case we need to look up the pbn lock. yes it's a just-in-case parameter, no i don't make the rules 🫠
  • counter_ptr — a pointer to the count for the data block. it's marked (in, out) so it goes in and comes back out, main character energy honestly 👑
  • adjust_block_count — whether to update the allocator's free block count. bool, so, you know, yes or no bestie ⭐

🌈 RETURN 🌈

VDO_SUCCESS or an error. that's the whole deal — slay or sad 😭

💜 SEE ALSO 💜

bestie this list is long and i refuse to lose a single one of them, so here's the whole crew 🫶 every name, exactly as it appears:

and the kernel file this whole thing lives in is ./drivers/md/dm-vdo/slab-depot.c — go read it, iykyk 💀

🎀 also, reminder: this page is from the kernel file ./drivers/md/dm-vdo, dated October 2026, and its official title is decrement_for_data(9). periodt. 💅✨🦋
📦 where this page comes from