bdi_get_by_id(9)

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

okay so picture this: you're deep in kernel-land, it's giving 9-section man page energy, and you need to find a bdi by its id. That's literally this whole page. Let's go 🫶

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✨ NAME ✨

bdi_get_by_id — lookup and get bdi from its id 🔍

🌸 SYNOPSIS 🌸

struct backing_dev_info * bdi_get_by_id (u64 id );

like, hand it an id and it hands you back a struct backing_dev_info *. iconic behavior honestly.

🎀 ARGUMENTS 🎀

• id — the bdi id you wanna look up. that's it. that's the whole argument. slay 💅

🦋 DESCRIPTION 🦋

So what it does: it finds the bdi that matches id and gets it. ✨

And here's the part you gotta remember, fr fr — it returns NULL if the matching bdi doesn't exist or is already unregistered. Both of those cases? NULL. No cap. So like, always check before you go dereferencing anything, bestie 😭💀

lowkey a vibe check: no match = NULL, already unregistered = also NULL. don't get caught out there 🙈

👑 SEE ALSO 👑

Kernel file ./mm/backing-dev.c plus these little icons:

• wb_get_lookup(9)
• wb_get_create(9)
• wb_memcg_offline(9)
• wb_blkcg_offline(9)

go read them, they're all in the same friend group fr 🌈

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and that's the page!! mwah 💖 this little gem lives over in ./mm, dated October 2026 — thank you for coming to my ted talk, go get that bdi 🧚‍♀️⭐