blkg_lookup_create(9)

💅 blkg_lookup_create(9) — the Kernel API Manual, but make it cute 🎀

okay bestie, so this is a page from the Kernel API Manual and it's literally all about blkg_lookup_create ✨ like, it's giving "find-or-make" energy and i'm obsessed. let's get into it 🫶

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✨ NAME ✨

blkg_lookup_create — lookup a blkg, and lowkey try to create one if it's not there 💖

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🌸 SYNOPSIS 🌸

struct blkcg_gq * blkg_lookup_create (struct blkcg *blkcg , struct gendisk *disk );

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🦋 ARGUMENTS 🦋

• blkcg — the blkcg of interest, aka the one we're looking at 👀
• disk — the gendisk of interest, bestie 🫶

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💜 DESCRIPTION 💜

so here's the vibe: this function looks up the blkg for the blkcg - disk pair. iconic pairing tbh. if it doesn't exist? no worries, it tries to create one ✨

and not me about to explain the recursion — blkg creation is performed recursively from blkcg_root, so that all non-root blkg's have access to the parent blkg. it's giving family tree, it's giving main character energy 🧚

⚠️ okay important caveat bestie: this function should be called under RCU read lock and it takes disk->queue->queue_lock. don't forget, i'm serious 😭

and the return? it returns the blkg, or the closest blkg if blkg_create fails as it walks down from root. so like, it still gives you something, which is nice of it fr fr 💅

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🌈 SEE ALSO 🌈

kernel file ./block/blk-cgroup.c and literally the whole friend group:

• blkcg_css(9)
• blkg_free(9)
• bio_blkcg_css(9)
• blkcg_parent(9)
• blkg_alloc(9)
• blkcg_print_blkgs(9)
• __blkg_prfill_u64(9)
• blkg_conf_init(9)
• blkg_conf_open_bdev(9)
• blkg_conf_prep(9)
• blkg_conf_unprep(9)
• blkg_conf_close_bdev(9)
• blkcg_destroy_blkgs(9)
• blkcg_pin_online(9)
• blkcg_unpin_online(9)
• blkcg_css_offline(9)
• blkcg_activate_policy(9)
• blkcg_deactivate_policy(9)
• blkcg_policy_register(9)
• blkcg_policy_unregister(9)
• blkcg_maybe_throttle_current(9)
• blkcg_schedule_throttle(9)
• blkcg_add_delay(9)
• blkg_tryget_closest(9)
• bio_associate_blkg_from_css(9)
• bio_associate_blkg(9)
• bio_clone_blkg_association(9)

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and that's the whole page bestie, no cap 🧢 this cutie lives in ./block and the version is Kernel API Manual, dated October 2026 — periodt, we ate and left no crumbs 💅✨💖