bio_copy_kern(9)

💖 bio_copy_kern — like, the whole vibe 💖

okay so bestie, welcome to bio_copy_kern(9) from the Kernel API Manual — section 9, kernel-space, extremely legit territory. sit down, grab a lil snack 🍓, and let's get into it.

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✨ NAME ✨

bio_copy_kern — the function that copies a kernel address right on into a bio 🫶

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✨ SYNOPSIS ✨

struct bio * bio_copy_kern (struct request *rq , void *data , unsigned
int len , gfp_t gfp_mask );

that's the whole signature, no cap. it hands you back a struct bio * 🌸

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✨ ARGUMENTS ✨

• rq — the request you're filling up. it's giving "this is the thing we're working with" 💅
• data — a pointer to the buffer you wanna copy. literally just point at it 🎀
• len — the length, in bytes. numbers, bestie, we love a unit 🔥
• gfp_mask — the allocation flags, and heads up: these cover both the bio allocation and the page allocation. two for one ✨

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✨ DESCRIPTION ✨

so what it actually does: it copies the kernel address into a bio that's suitable for io to a block device. that's the whole job, and it ate 👑

and if something goes sideways? it returns an error pointer. so like… check your return value, babes, it's not always gonna be a happy lil bio 😭

fr fr, error pointer means error. don't just start dereferencing and hope for the best 🙈

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✨ SEE ALSO ✨

sibling functions, the whole friend group 🧚:

• bio_copy_from_iter(9)
• bio_copy_to_iter(9)
• bio_uncopy_user(9)
• blk_rq_map_user_iov(9)
• blk_rq_unmap_user(9)
• blk_rq_map_kern(9)

and they all live together in the kernel file ./block/blk-map.c — iconic address ngl 💜

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🌈 bye bestie 🌈

this lil page came out of the ./block directory, dated October 2026, in the Kernel API Manual, section 9, under the name bio_copy_kern(9). mwah, go read some block layer code, i'm obsessed with you 💖💅✨