blkg_rwstat_recursive_sum(9)

🌸 blkg_rwstat_recursive_sum(9) 🌸

okay bestie, welcome to the Kernel API Manual — this one's a little blkcg deep-dive and honestly it's giving "summon the whole family tree" energy 💅

---

✨ NAME ✨

blkg_rwstat_recursive_sum — collect hierarchical blkg_rwstat 🎀

---

🦋 SYNOPSIS 🦋

void blkg_rwstat_recursive_sum (struct blkcg_gq *blkg , struct
       blkcg_policy *pol , int off , struct blkg_rwstat_sample *sum );

---

💖 ARGUMENTS 💖

• blkg — the blkg of interest 👀 like, the one you actually care about
• pol — the blkcg_policy that contains the blkg_rwstat
• off — the offset to the blkg_rwstat in blkg_policy_data or blkg
• sum — your blkg_rwstat_sample structure, aka where the results go 🫶

---

🌈 DESCRIPTION 🌈

So what this does: it collects the blkg_rwstat specified by blkg, pol and off and all its online descendants and their aux counts. the way it just scoops up the entire lineage… obsessed 😭

And here's the branching logic, no cap:

• if pol is NULL, the blkg_rwstat is at off bytes into blkg
• otherwise, it's at off bytes into blkg's blkg_policy_data of the policy ✨

fr fr, that pol check is the whole vibe check of this function — NULL means "raw offset into blkg", non-NULL means "go through the policy's blkg_policy_data". don't mix them up 💀

---

👑 SEE ALSO 👑

• Kernel file ./block/blk-cgroup-rwstat.c
• __blkg_prfill_rwstat(9)
• blkg_prfill_rwstat(9)

---

okay that's the whole thing, you ate that 🍓💜 — this cutie lives in the ./block source tree and the file's dated October 2026. go forth and recurse, bestie 🧚✨