bio_blkcg_css(9)

💅 bio_blkcg_css 💅

okay so this is a page from the Kernel API Manual bestie, and it's literally about one tiny function that does one tiny thing but honestly? kind of iconic. let's get into it 🎀

---

✨ NAME ✨

bio_blkcg_css — return the blkcg CSS associated with a bio

like, that's the whole job. one bio in, one CSS out. slay.

---

🦋 SYNOPSIS 🦋

struct cgroup_subsys_state * bio_blkcg_css (struct bio *bio );

that's the whole signature. struct cgroup_subsys_state * coming at ya, takes a struct bio *bio, and it's giving "small but mighty" energy fr fr 🔥

---

🌸 ARGUMENTS 🌸

• bio — the target bio. that's it. that's the argument. the bio you're curious about. the main character, if you will 👑

---

💖 DESCRIPTION 💖

so here's the tea: this function returns the CSS for the blkcg that's associated with a bio. that's it. that's the vibe. it hands you the CSS and you go on with your day ✨

but okay, plot twist — if the bio isn't associated with anything, you get NULL back. no CSS, no cgroup, just void 😭

and here's the part you actually need to pay attention to, bestie:

callers are expected to either handle NULL or know that the association has already been done before they call this. it's not gonna do it for you. no cap.

so like. either you check for NULL like a responsible legend, or you already know damn well the association happened earlier. there is no third option. vibe check passed? good. 💅

---

🔥 SEE ALSO 🔥

okay this is the part where the manpage goes full friend-group-intro and lists literally everyone. all of these live in the kernel file ./block/blk-cgroup.c:

• blkcg_css(9)
• blkg_free(9)
• blkcg_parent(9)
• blkg_alloc(9)
• blkg_lookup_create(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)

twenty-seven functions. twenty-seven. the whole squad showed up and honestly? respect 🫶

---

and that's the page!! sourced from the directory ./block, dated October 2026, and published under the header bio_blkcg_css(9) 💜 go forth and check your NULLs bestie, ily, bye 🧚⭐