rq_qos_wait(9)

🌸 rq_qos_wait — kernel API manual, but make it make sense 🌸

okay bestie, welcome to the Kernel API Manual entry for rq_qos_wait(9) 💅 this one's a little throttle-y helper and honestly? she's iconic. let's get into it ✨

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✨ NAME ✨

rq_qos_wait — throttle on a rqw if we need to 🫶

like, only if we actually need to. no cap.

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🎀 SYNOPSIS 🎀

void rq_qos_wait (struct rq_wait *rqw , void *private_data ,
acquire_inflight_cb_t *acquire_inflight_cb , cleanup_cb_t *cleanup_cb );

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🦋 ARGUMENTS 🦋

• rqw — the rqw you're throttling on. yeah. that one. 👀
• private_data — caller-provided specific data, i.e. your own little bag of stuff you're bringing to the function 🎒
• acquire_inflight_cb — the callback that incs the rqw->inflight counter if we can. if we can't? it says no and we go night-night 😴
• cleanup_cb — the callback to cleanup in case we race with a waker 🏃‍♀️💨

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🌈 DESCRIPTION 🌈

so the whole point of this one is to give all the rq_qos users one uniform place to do their throttling. literally one spot. main character energy 🎀

and the reason it matters: since you can end up with a lot of things sleeping at once, this thing manages the waking up based on the resources available. it's giving traffic control but make it ✨elegant✨

the acquire_inflight_cb should inc the rqw->inflight if we have the ability to do so. and if we don't? it returns false, and then we will sleep until the room becomes available. periodt. 💤

cleanup_cb is there for in case we race with a waker and need to cleanup the inflight count accordingly — because races happen, and we handle them, slay 🫶

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💜 SEE ALSO 💜

• Kernel file ./block/blk-rq-qos.c

go read the source bestie, iykyk 🔥

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ok tiny vibe check: this is kernel-side throttling, so don't go calling it from your random userspace program thinking it's gonna sort your life out 🙈 also the callbacks are your responsibility — if your acquire_inflight_cb lies about grabbing the inflight slot, that's on you, not on the helper 💀

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and that's the page!! 🍓 this one's from the ./block source, in the Kernel API Manual, dated October 2026 — rq_qos_wait(9), mwah 💋 bye bestie, go throttle responsibly 🧚‍♀️💖