blk_update_request(9)

📦 version 7.3.1, in nixpkgs unstable

💅 blk_update_request — from the Kernel API Manual, bestie (section 9, kernel-space era) ✨

Okay so this one's called blk_update_request and it's literally the "finish some bytes but not the whole vibe" function. Let's get into it 🫶

🌸 NAME 🌸

blk_update_request — complete multiple bytes without completing the request. Yes, that's the whole bit. Partially finish it. Iconic behaviour honestly 💅

✨ SYNOPSIS ✨

bool blk_update_request (struct request *req , blk_status_t error ,
       unsigned int nr_bytes );

Three args, returns a bool, and it's giving "I do exactly one thing and I do it well" 💖

🎀 ARGUMENTS 🎀

  • req — the request being processed. The main character of this whole function, no cap 👑
  • error — block status code. It's a blk_status_t, so you know it's official ⭐
  • nr_bytes — number of bytes to complete for req. How much of the request you're finishing off rn 🍓

🦋 DESCRIPTION 🦋

So what it actually does: it ends I/O on a number of bytes attached to req. Note the number of bytes phrasing — it does not complete the request structure itself, even if req doesn't have any leftover. Like, it'll finish the bytes but the struct is still standing there, untouched, thriving 🌈

But if req does have leftover, then it sets it up for the next range of segments. Lowkey it's handing off the baton 🏃‍♀️

And here's the fun fact: passing the result of blk_rq_bytes as nr_bytes guarantees a false return from this function. Guarantees it. No notes. 🔥

💀 NOTE 💀

The RQF_SPECIAL_PAYLOAD flag is ignored on purpose in this function — except in the consistency check at the end of this function. So like, not ignored-ignored, just ignored until the last second. Respect the pipeline honestly 🙈

Fr fr don't "fix" that one, it's intentional 💅

⭐ RETURN ⭐

  • false — this request doesn't have any more data
  • true — this request has more data

That's it, that's the whole vibe check 💖

🧚 SEE ALSO 🧚

Kernel file ./block/blk-mq.c, plus this absolutely stacked lineup of siblings:

A whole friend group. Go read all of them, iykyk 🌸

And that's the page!! It lives in ./block and this particular rendering is dated October 2026 — so like, mark your calendar bestie 🎀✨ Byeee, go finish some bytes (but not the whole request) 💜🦋

📦 where this page comes from