STRUCT CEPH_SUBVOLUME_METRICS_TRACKER(9)

struct ceph_subvolume_metrics_tracker(9) 💅

okay so this is the Kernel API Manual, bestie, and today's main character is a struct that literally keeps receipts on your per-subvolume I/O. no cap, it's giving accounting-department-but-make-it-glam. ✨

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🌸 NAME 🌸

struct ceph_subvolume_metrics_tracker — tracks per-subvolume I/O metrics 🎀

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🦋 SYNOPSIS 🦋

struct ceph_subvolume_metrics_tracker {
    spinlock_t lock;
    struct rb_root_cached tree;
    u32 nr_entries;
    bool enabled;
    atomic64_t snapshot_attempts;
    atomic64_t snapshot_empty;
    atomic64_t snapshot_failures;
    atomic64_t record_calls;
    atomic64_t record_disabled;
    atomic64_t record_no_subvol;
    atomic64_t total_read_ops;
    atomic64_t total_read_bytes;
    atomic64_t total_write_ops;
    atomic64_t total_write_bytes;
 };

like, look at her. so organized. so many counters. she's booked and busy 💜

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👑 Members 👑

• lock — the bouncer at the door 🫶 protects tree and nr_entries during concurrent access, so nobody's out here writing while someone else is reading. we love a safety queen.
• tree — a red-black tree of per-subvolume entries, keyed by subvolume_id. literally the whole point of the struct, she holds everyone's little folder 📁
• nr_entries — the number of entries currently in tree. simple. iconic. a headcount.
• enabled — whether collection is enabled (and yeah, it requires MDS feature support — no feature, no vibes 💀).
• snapshot_attempts — debug counter: total ceph_subvolume_metrics_snapshot calls. she be counting attempts fr fr.
• snapshot_empty — debug counter: snapshots that found no data to report. the "nothing to see here" count 🙈
• snapshot_failures — debug counter: snapshots that failed to allocate memory. 😭 the sad ones.
• record_calls — debug counter: total ceph_subvolume_metrics_record calls.
• record_disabled — debug counter: record calls skipped because disabled. not her fault, she was literally off duty.
• record_no_subvol — debug counter: record calls skipped (no subvolume_id). no id, no entry, that's the rule bestie ✨
• total_read_ops — cumulative read ops across all snapshots (never reset — like, ever. periodt.)
• total_read_bytes — cumulative bytes read across all snapshots (never reset 💅)
• total_write_ops — cumulative write ops across all snapshots (never reset 🔥)
• total_write_bytes — cumulative bytes written across all snapshots (never reset 👑)

ngl the four total_* counters are the real ones — they never reset, so they just keep climbing forever. respect the grind. 🌈

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💖 SEE ALSO 💖

• Kernel file ./fs/ceph/subvolume_metrics.h struct
• ceph_subvol_metric_snapshot(9)

go read those too, iykyk 🧚

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and that's the whole page, bestie! this lil beauty lives in ./fs/ceph and the version vibes are dated October 2026 — see you in the future, mwah! 💕🎀🦋🌺🍓⭐💜