blk_rq_unmap_user(9)

💅 blk_rq_unmap_user(9) — from the Kernel API Manual, bestie

okay so picture this: you mapped a request with user data, and now you gotta un-map it. that's the whole gig. it's giving cleanup era ✨ and honestly? iconic. 🎀

No cap, this page lives in the Kernel API Manual, so you already know it's the real deal. 🫶

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✨ SYNOPSIS ✨

int blk_rq_unmap_user (struct bio *bio );

that's it. one function, one arg, returns an int. slay. 💅

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🦋 ARGUMENTS 🦋

• bio — start of bio list. literally just the beginning of the bio list, that's the whole vibe. 🌸

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🔥 DESCRIPTION 🔥

so what does it actually do?? it unmaps a rq that was previously mapped by blk_rq_map_user. simple as that. ✨

but here's the part you CANNOT skip, bestie, pay attention 👀: the caller must supply the original rq->bio from the blk_rq_map_user return, because the I/O completion may have changed rq->bio. 😭

fr fr, do not just grab whatever rq->bio is sitting there when you call this — the I/O completion may have changed it, and that is not the move. keep the original one from the blk_rq_map_user return. periodt. 💀

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👑 SEE ALSO 👑

• Kernel file ./block/blk-map.c
• bio_copy_from_iter(9)
• bio_copy_to_iter(9)
• bio_uncopy_user(9)
• bio_copy_kern(9)
• blk_rq_map_user_iov(9)
• blk_rq_map_kern(9)

go read those too, iykyk 🧚💜

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🌈 cute lil sign-off 🌈

this whole page came from the ./block source, and it's dated October 2026 — so yeah, freshly stamped and everything ⭐. mwah, go unmap those requests responsibly, bestie 💖🍓