Merge branch 'main' into overtrue/backlog-1823-step10-batch3

Replace every bare `#[allow(dead_code)]` in ecstore with either a deletion or a per-item allow carrying a `reason`. Blanket allows at module, struct, and impl level silence the lint for future members too, so each is narrowed to the members that are actually dead.

Delete the dead cluster in `config/heal.rs` (`Config`, its three methods, `RUSTFS_BITROT_CYCLE_IN_MONTHS`, `parse_bitrot_config`) rather than annotate it: it has no callers and is unreachable outside the crate, and `parse_bitrot_config` would panic on its disabled path via `Duration::from_secs_f64(-1.0)`. `DEFAULT_KVS` stays, since the config registry uses it.

Correct two `reason` strings on `Checksum::new` and `PutObjReader::md5_current_hex_string`, which are methods but carried a field-only rationale.

Refs backlog#1823

crates/data-usage/src/data_usage.rs

@@ -870,6 +870,157 @@ pub struct DataUsageCacheInfo {
     pub snapshot_complete: bool,
 }
 
+/// Prefix-level usage over a raw entry map — the shared core behind
+/// [`DataUsageCache::prefix_usage`], usable by any cache-shaped reader (the
+/// scanner's writer-side cache has the same map type).
+///
+/// Cache keys are cleaned literal paths (`bucket/pre/fix`), so sub-prefix
+/// names come straight off the child keys — no reverse mapping exists or is
+/// needed. A compacted prefix carries its aggregate but no children, which
+/// the `compacted` flag reports so callers can say why the breakdown is
+/// empty. `truncated` is set when the breakdown exceeded `max_entries` and
+/// was cut (largest first).
+pub fn prefix_usage_in_cache(
+    cache: &HashMap<String, DataUsageEntry>,
+    bucket: &str,
+    prefix: &str,
+    max_entries: usize,
+) -> Option<PrefixUsageQuery> {
+    let prefix = prefix.trim_matches('/');
+    let root = if prefix.is_empty() {
+        bucket.to_string()
+    } else {
+        format!("{bucket}/{prefix}")
+    };
+    let entry = cache.get(&hash_path(&root).key())?.clone();
+
+    let usage = PrefixUsageSummary::from_entry(&flatten_entry(cache, &entry, 0)?);
+
+    let child_prefix = format!("{root}/");
+    let mut sub_prefixes: Vec<PrefixUsageEntry> = entry
+        .children
+        .iter()
+        .filter_map(|child_key| {
+            let child = cache.get(child_key)?;
+            let child_flat = flatten_entry(cache, child, 1)?;
+            // Child keys are literal `bucket/pre/name` paths; a trailing
+            // slash marks a directory object and is display-only here.
+            let name = child_key
+                .strip_prefix(child_prefix.as_str())
+                .unwrap_or(child_key.as_str())
+                .trim_end_matches('/')
+                .to_string();
+            Some(PrefixUsageEntry {
+                prefix: name,
+                usage: PrefixUsageSummary::from_entry(&child_flat),
+            })
+        })
+        .collect();
+    sub_prefixes.sort_by(|left, right| {
+        right
+            .usage
+            .size
+            .cmp(&left.usage.size)
+            .then_with(|| left.prefix.cmp(&right.prefix))
+    });
+    let truncated = sub_prefixes.len() > max_entries;
+    sub_prefixes.truncate(max_entries);
+
+    Some(PrefixUsageQuery {
+        usage,
+        compacted: entry.compacted,
+        truncated,
+        sub_prefixes,
+    })
+}
+
+/// Maximum subtree depth [`flatten_entry`] will walk before declaring the
+/// cache corrupt — the same bound the scanner's checked flatten uses.
+const PREFIX_USAGE_MAX_DEPTH: usize = 1024;
+
+/// Flatten one entry's subtree into an aggregate: the free-function twin of
+/// [`DataUsageCache::flatten`], carrying the scanner checked-flatten
+/// hardening so a corrupt cache (cycles, over-deep trees, overflowing
+/// counters) yields `None` instead of unbounded recursion or wrapped totals.
+fn flatten_entry(cache: &HashMap<String, DataUsageEntry>, root: &DataUsageEntry, depth: usize) -> Option<DataUsageEntry> {
+    if depth > PREFIX_USAGE_MAX_DEPTH {
+        return None;
+    }
+    let mut flattened = DataUsageEntry::default();
+    if !flattened.checked_merge(root) {
+        return None;
+    }
+    flattened.compacted = root.compacted;
+    // The root itself is not pre-seeded: it is merged above, and a corrupt
+    // child edge pointing back at the root's own key is still terminated by
+    // the visited set on first encounter.
+    let mut visited: HashSet<&str> = HashSet::new();
+    let mut pending: Vec<(&String, usize)> = root.children.iter().map(|child| (child, depth + 1)).collect();
+    while let Some((key, child_depth)) = pending.pop() {
+        if child_depth > PREFIX_USAGE_MAX_DEPTH || !visited.insert(key.as_str()) {
+            return None;
+        }
+        let entry = cache.get(key)?;
+        if !flattened.checked_merge(entry) {
+            return None;
+        }
+        pending.extend(entry.children.iter().map(|child| (child, child_depth + 1)));
+    }
+    flattened.children.clear();
+    Some(flattened)
+}
+
+/// Flattened counters of one prefix subtree, as returned by
+/// [`DataUsageCache::prefix_usage`].
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, serde::Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct PrefixUsageSummary {
+    pub size: u64,
+    pub objects: u64,
+    pub versions: u64,
+    pub delete_markers: u64,
+}
+
+impl PrefixUsageSummary {
+    fn from_entry(entry: &DataUsageEntry) -> Self {
+        Self {
+            size: entry.size as u64,
+            objects: entry.objects as u64,
+            versions: entry.versions as u64,
+            delete_markers: entry.delete_markers as u64,
+        }
+    }
+
+    /// Add another set's counters into this one (entries are partitioned by
+    /// set, so per-set results sum).
+    pub fn merge(&mut self, other: &Self) {
+        self.size = self.size.saturating_add(other.size);
+        self.objects = self.objects.saturating_add(other.objects);
+        self.versions = self.versions.saturating_add(other.versions);
+        self.delete_markers = self.delete_markers.saturating_add(other.delete_markers);
+    }
+}
+
+/// One first-level sub-prefix row of a [`PrefixUsageQuery`].
+#[derive(Clone, Debug, PartialEq, Eq, serde::Serialize)]
+pub struct PrefixUsageEntry {
+    pub prefix: String,
+    pub usage: PrefixUsageSummary,
+}
+
+/// Result of [`DataUsageCache::prefix_usage`].
+#[derive(Clone, Debug, Default, PartialEq, Eq, serde::Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct PrefixUsageQuery {
+    pub usage: PrefixUsageSummary,
+    /// The prefix entry was compacted by the scanner: its aggregate is valid
+    /// but no sub-prefix breakdown exists on disk.
+    pub compacted: bool,
+    /// The breakdown had more entries than `max_entries`; the largest remain.
+    pub truncated: bool,
+    pub sub_prefixes: Vec<PrefixUsageEntry>,
+}
+
 /// Read-only projection of a scanner-written `.usage-cache.bin` file.
 ///
 /// The scanner-side `DataUsageCache` (`crates/scanner/src/data_usage_define.rs`)
@@ -997,6 +1148,21 @@ impl DataUsageCache {
         }
     }
 
+    /// Prefix-level usage for one bucket subtree, plus the one-level
+    /// breakdown below it (rustfs/backlog#1872, MinIO
+    /// `loadPrefixUsageFromBackend` parity and beyond: arbitrary prefixes and
+    /// full counters instead of first-level sizes only).
+    ///
+    /// Cache keys are cleaned literal paths (`bucket/pre/fix`), so sub-prefix
+    /// names come straight off the child keys — no reverse mapping exists or
+    /// is needed. A compacted prefix carries its aggregate but no children,
+    /// which the `compacted` flag reports so callers can say why the
+    /// breakdown is empty. `truncated` is set when the breakdown exceeded
+    /// `max_entries` and was cut (largest first).
+    pub fn prefix_usage(&self, bucket: &str, prefix: &str, max_entries: usize) -> Option<PrefixUsageQuery> {
+        prefix_usage_in_cache(&self.cache, bucket, prefix, max_entries)
+    }
+
     pub fn force_compact(&mut self, limit: usize) {
         if self.cache.len() < limit {
             return;
@@ -1898,6 +2064,126 @@ mod tests {
         );
     }
 
+    /// Build a cache shaped like `bucket/{a,b/{c,d}},bucket/loose` with
+    /// distinct counters so aggregation is observable.
+    fn prefix_usage_fixture_cache() -> DataUsageCache {
+        let mut cache = DataUsageCache::default();
+        let mut insert = |path: &str, parent: &str, size: usize, objects: usize, versions: usize, delete_markers: usize| {
+            cache.replace(
+                path,
+                parent,
+                DataUsageEntry {
+                    size,
+                    objects,
+                    versions,
+                    delete_markers,
+                    ..Default::default()
+                },
+            );
+        };
+        insert("bucket", "", 0, 0, 0, 0);
+        insert("bucket/a", "bucket", 100, 1, 1, 0);
+        insert("bucket/b", "bucket", 0, 0, 0, 0);
+        insert("bucket/b/c", "bucket/b", 200, 2, 2, 1);
+        insert("bucket/b/d", "bucket/b", 40, 1, 3, 0);
+        insert("bucket/loose", "bucket", 10, 1, 1, 1);
+        cache
+    }
+
+    #[test]
+    fn prefix_usage_aggregates_bucket_root_and_one_level_below() {
+        let cache = prefix_usage_fixture_cache();
+
+        let root = cache
+            .prefix_usage("bucket", "", 100)
+            .expect("root query must find the bucket entry");
+        assert_eq!(root.usage.size, 350, "root aggregate flattens the whole subtree");
+        assert_eq!(root.usage.objects, 5);
+        assert_eq!(root.usage.versions, 7);
+        assert_eq!(root.usage.delete_markers, 2);
+        assert!(!root.compacted);
+        assert!(!root.truncated);
+        // Breakdown is one level: b (240) before a (100) before loose (10),
+        // each flattened to its own subtree total.
+        let names: Vec<(&str, u64)> = root
+            .sub_prefixes
+            .iter()
+            .map(|entry| (entry.prefix.as_str(), entry.usage.size))
+            .collect();
+        assert_eq!(names, vec![("b", 240), ("a", 100), ("loose", 10)]);
+    }
+
+    #[test]
+    fn prefix_usage_drills_into_arbitrary_prefixes() {
+        let cache = prefix_usage_fixture_cache();
+
+        let b = cache.prefix_usage("bucket", "b", 100).expect("nested prefix must resolve");
+        assert_eq!(b.usage.size, 240);
+        assert_eq!(b.usage.versions, 5);
+        let names: Vec<&str> = b.sub_prefixes.iter().map(|entry| entry.prefix.as_str()).collect();
+        assert_eq!(names, vec!["c", "d"]);
+
+        // Prefix slashes are normalized away.
+        let slashed = cache.prefix_usage("bucket", "/b/", 100).expect("slash-insensitive lookup");
+        assert_eq!(slashed.usage.size, 240);
+
+        assert!(cache.prefix_usage("bucket", "absent", 100).is_none(), "unknown prefix must be a miss");
+        assert!(cache.prefix_usage("other", "", 100).is_none(), "unknown bucket must be a miss");
+    }
+
+    #[test]
+    fn prefix_usage_reports_and_respects_truncation() {
+        let cache = prefix_usage_fixture_cache();
+        let capped = cache.prefix_usage("bucket", "", 2).expect("root query");
+        assert!(capped.truncated, "three children capped to two must flag truncation");
+        let names: Vec<&str> = capped.sub_prefixes.iter().map(|entry| entry.prefix.as_str()).collect();
+        assert_eq!(names, vec!["b", "a"], "largest prefixes survive the cut");
+    }
+
+    #[test]
+    fn prefix_usage_marks_compacted_entries() {
+        let mut cache = DataUsageCache::default();
+        cache.replace(
+            "bucket",
+            "",
+            DataUsageEntry {
+                size: 999,
+                objects: 9,
+                compacted: true,
+                ..Default::default()
+            },
+        );
+
+        let compacted = cache.prefix_usage("bucket", "", 100).expect("compacted root resolves");
+        assert!(compacted.compacted, "compaction must be visible to callers");
+        assert_eq!(compacted.usage.size, 999);
+        assert!(compacted.sub_prefixes.is_empty(), "a compacted entry carries no children");
+    }
+
+    #[test]
+    fn prefix_usage_rejects_cyclic_and_dangling_caches() {
+        // A self-referencing child (corrupt cache) must yield a miss for the
+        // whole query, not unbounded recursion.
+        let mut cache = prefix_usage_fixture_cache();
+        if let Some(entry) = cache.cache.get_mut("bucket/b") {
+            entry.children.insert("bucket/b".to_string());
+        }
+        assert!(cache.prefix_usage("bucket", "b", 100).is_none(), "a cyclic subtree must be rejected");
+        // The unaffected sibling still answers.
+        assert!(cache.prefix_usage("bucket", "a", 100).is_some());
+
+        // A child key with no entry (dangling link) is rejected rather than
+        // silently dropped: half a tree would under-report usage.
+        let mut dangling = prefix_usage_fixture_cache();
+        if let Some(entry) = dangling.cache.get_mut("bucket/b") {
+            entry.children.insert("bucket/b/ghost".to_string());
+        }
+        assert!(
+            dangling.prefix_usage("bucket", "b", 100).is_none(),
+            "a dangling child link must be rejected"
+        );
+    }
+
     #[test]
     fn hash_path_uses_portable_slash_semantics() {
         for (input, expected) in [

crates/ecstore/src/bucket/bucket_target_sys.rs

@@ -1549,8 +1549,8 @@ impl Default for PutObjectOptions {
     }
 }
 
-#[allow(dead_code)]
 impl PutObjectOptions {
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn set_match_etag(&mut self, etag: &str) {
         if etag == "*" {
             self.custom_header
@@ -1561,6 +1561,7 @@ impl PutObjectOptions {
         }
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn set_match_etag_except(&mut self, etag: &str) {
         if etag == "*" {
             self.custom_header
@@ -1696,6 +1697,7 @@ impl PutObjectOptions {
         header
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn validate(&self, _c: Arc<TargetClient>) -> Result<(), std::io::Error> {
         //if self.checksum.is_set() {
         /*if !self.trailing_header_support {

crates/ecstore/src/bucket/lifecycle/bucket_lifecycle_ops.rs

@@ -456,16 +456,23 @@ impl<'a> LifecycleExpiryTrace<'a> {
     }
 }
 
-#[allow(dead_code)]
 impl ExpiryStats {
     pub fn missed_tasks(&self) -> i64 {
         self.missed_expiry_tasks.load(Ordering::SeqCst)
     }
 
+    #[allow(
+        dead_code,
+        reason = "asserted by this file's tests; the lib target cannot see test-only consumers (backlog#1823)"
+    )]
     fn missed_free_vers_tasks(&self) -> i64 {
         self.missed_freevers_tasks.load(Ordering::SeqCst)
     }
 
+    #[allow(
+        dead_code,
+        reason = "asserted by this file's tests; the lib target cannot see test-only consumers (backlog#1823)"
+    )]
     fn missed_tier_journal_tasks(&self) -> i64 {
         self.missed_tier_journal_tasks.load(Ordering::SeqCst)
     }

crates/ecstore/src/bucket/lifecycle/tier_last_day_stats.rs

@@ -80,7 +80,10 @@ impl LastDayTierStats {
         }
     }
 
-    #[allow(dead_code)]
+    #[allow(
+        dead_code,
+        reason = "asserted by this file's tests; the lib target cannot see test-only consumers (backlog#1823)"
+    )]
     fn merge(&self, m: LastDayTierStats) -> LastDayTierStats {
         let mut cl = self.clone();
         let mut cm = m;

crates/ecstore/src/bucket/lifecycle/tier_sweeper.rs

@@ -177,9 +177,10 @@ fn should_record_remote_delete_failure(err: &std::io::Error) -> bool {
 }
 
 #[derive(Default)]
-#[allow(dead_code)]
 struct ObjSweeper {
+    #[allow(dead_code, reason = "written but never read back (backlog#1823)")]
     object: String,
+    #[allow(dead_code, reason = "written but never read back (backlog#1823)")]
     bucket: String,
     version_id: Option<Uuid>,
     versioned: bool,
@@ -191,9 +192,9 @@ struct ObjSweeper {
     remote_object: String,
 }
 
-#[allow(dead_code)]
 impl ObjSweeper {
     #[allow(clippy::new_ret_no_self)]
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub async fn new(bucket: &str, object: &str) -> Result<Self, std::io::Error> {
         Ok(Self {
             object: object.into(),
@@ -202,17 +203,20 @@ impl ObjSweeper {
         })
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub fn with_version(&mut self, vid: Option<Uuid>) -> &Self {
         self.version_id = vid.clone();
         self
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub fn with_versioning(&mut self, versioned: bool, suspended: bool) -> &Self {
         self.versioned = versioned;
         self.suspended = suspended;
         self
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub fn get_opts(&self) -> lifecycle::ObjectOpts {
         let mut opts = ObjectOpts {
             version_id: self.version_id.clone(),
@@ -226,6 +230,7 @@ impl ObjSweeper {
         opts
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub fn set_transition_state(&mut self, info: TransitionedObject) {
         self.transition_tier = info.tier;
         self.transition_status = info.status;
@@ -266,6 +271,7 @@ impl ObjSweeper {
         None
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub async fn sweep(&self, api: Arc<ECStore>) {
         let Some(je) = self.should_remove_remote_object() else {
             return;

crates/ecstore/src/bucket/quota/mod.rs

@@ -312,9 +312,7 @@ mod tests {
         }
         #[derive(Deserialize)]
         struct LegacyBucketQuota {
-            #[allow(dead_code)]
             quota: Option<u64>,
-            #[allow(dead_code)]
             quota_type: LegacyQuotaType,
         }
         let legacy = serde_json::from_slice::<LegacyBucketQuota>(&json)

crates/ecstore/src/client/api_get_object.rs

@@ -95,7 +95,6 @@ impl TransitionClient {
 }
 
 #[derive(Default)]
-#[allow(dead_code)]
 pub struct GetRequest {
     pub buffer: Vec<u8>,
     pub offset: i64,
@@ -107,11 +106,12 @@ pub struct GetRequest {
     pub setting_object_info: bool,
 }
 
-#[allow(dead_code)]
 pub struct GetResponse {
     pub size: i64,
     //pub error:       error,
+    #[allow(dead_code, reason = "written but never read back (backlog#1823)")]
     pub did_read: bool,
+    #[allow(dead_code, reason = "written but never read back (backlog#1823)")]
     pub object_info: ObjectInfo,
 }
 

crates/ecstore/src/client/api_get_options.rs

@@ -27,7 +27,6 @@ use tracing::warn;
 use crate::client::api_error_response::err_invalid_argument;
 
 #[derive(Default)]
-#[allow(dead_code)]
 pub struct AdvancedGetOptions {
     pub replication_delete_marker: bool,
     pub is_replication_ready_for_delete_marker: bool,

crates/ecstore/src/client/api_list.rs

@@ -360,7 +360,6 @@ impl TransitionClient {
 }
 
 #[derive(Default)]
-#[allow(dead_code)]
 pub struct ListObjectsOptions {
     reverse_versions: bool,
     with_versions: bool,

crates/ecstore/src/client/api_put_object.rs

@@ -137,8 +137,8 @@ impl Default for PutObjectOptions {
     }
 }
 
-#[allow(dead_code)]
 impl PutObjectOptions {
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn set_match_etag(&mut self, etag: &str) {
         if etag == "*" {
             self.custom_header.insert("If-Match", HeaderValue::from_static("*"));
@@ -149,6 +149,7 @@ impl PutObjectOptions {
         }
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn set_match_etag_except(&mut self, etag: &str) {
         if etag == "*" {
             self.custom_header.insert("If-None-Match", HeaderValue::from_static("*"));
@@ -259,6 +260,7 @@ impl PutObjectOptions {
         header
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn validate(&self, c: TransitionClient) -> Result<(), std::io::Error> {
         //if self.checksum.is_set() {
         /*if !self.trailing_header_support {

crates/ecstore/src/client/api_remove.rs

@@ -55,7 +55,6 @@ pub struct RemoveBucketOptions {
 const DELETE_RESPONSE_PREVIEW_LEN: usize = 1024;
 
 #[derive(Debug)]
-#[allow(dead_code)]
 pub struct AdvancedRemoveOptions {
     pub replication_delete_marker: bool,
     pub replication_status: ReplicationStatus,
@@ -465,10 +464,10 @@ impl TransitionClient {
 }
 
 #[derive(Debug, Default)]
-#[allow(dead_code)]
 pub struct RemoveObjectError {
+    #[allow(dead_code, reason = "written but never read back (backlog#1823)")]
     object_name: String,
-    #[allow(dead_code)]
+    #[allow(dead_code, reason = "written but never read back (backlog#1823)")]
     version_id: String,
     err: Option<std::io::Error>,
 }

crates/ecstore/src/client/checksum.rs

@@ -372,8 +372,8 @@ pub struct Checksum {
     computed: bool,
 }
 
-#[allow(dead_code)]
 impl Checksum {
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn new(t: ChecksumMode, b: &[u8]) -> Checksum {
         if t.is_set() && b.len() == t.raw_byte_len() {
             return Checksum {
@@ -385,7 +385,7 @@ impl Checksum {
         Checksum::default()
     }
 
-    #[allow(dead_code)]
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn new_checksum_string(t: ChecksumMode, s: &str) -> Result<Checksum, std::io::Error> {
         let b = match base64_decode(s.as_bytes()) {
             Ok(b) => b,
@@ -412,7 +412,7 @@ impl Checksum {
         base64_encode(&self.r)
     }
 
-    #[allow(dead_code)]
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn raw(&self) -> Option<Vec<u8>> {
         if !self.is_set() {
             return None;

crates/ecstore/src/client/object_api_utils.rs

@@ -37,16 +37,17 @@ pub struct PutObjReader {
     //pub sealMD5Fn: SealMD5CurrFn,
 }
 
-#[allow(dead_code)]
 impl PutObjReader {
     pub fn new(reader: HashReader) -> Self {
         Self { reader }
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn md5_current_hex_string(&self) -> String {
         self.reader.checksum().map(|v| v.encoded).unwrap_or_default()
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn with_encryption(&mut self, enc_reader: HashReader) -> Result<(), std::io::Error> {
         self.reader = enc_reader;
 

crates/ecstore/src/config/audit.rs

@@ -39,7 +39,6 @@ use rustfs_config::{
 };
 use std::sync::LazyLock;
 
-#[allow(dead_code)]
 #[allow(clippy::declare_interior_mutable_const)]
 /// Default KVS for audit webhook settings.
 pub static DEFAULT_AUDIT_WEBHOOK_KVS: LazyLock<KVS> = LazyLock::new(|| {
@@ -117,7 +116,6 @@ pub static DEFAULT_AUDIT_WEBHOOK_KVS: LazyLock<KVS> = LazyLock::new(|| {
     ])
 });
 
-#[allow(dead_code)]
 #[allow(clippy::declare_interior_mutable_const)]
 /// Default KVS for audit MQTT settings.
 pub static DEFAULT_AUDIT_MQTT_KVS: LazyLock<KVS> = LazyLock::new(|| {
@@ -375,7 +373,6 @@ pub static DEFAULT_AUDIT_NATS_KVS: LazyLock<KVS> = LazyLock::new(|| {
     ])
 });
 
-#[allow(dead_code)]
 pub static DEFAULT_AUDIT_PULSAR_KVS: LazyLock<KVS> = LazyLock::new(|| {
     KVS(vec![
         KV {

crates/ecstore/src/config/heal.rs

@@ -12,12 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use crate::error::{Error, Result};
 use rustfs_config::server_config::{KV, KVS};
 use rustfs_config::{DEFAULT_HEAL_BITROT_CYCLE_SECS, HEAL_BITROT_CYCLE};
-use rustfs_utils::string::parse_bool;
 use std::sync::LazyLock;
-use std::time::Duration;
 
 pub static DEFAULT_KVS: LazyLock<KVS> = LazyLock::new(|| {
     KVS(vec![KV {
@@ -26,59 +23,3 @@ pub static DEFAULT_KVS: LazyLock<KVS> = LazyLock::new(|| {
         hidden_if_empty: false,
     }])
 });
-
-#[derive(Debug, Default)]
-pub struct Config {
-    pub bitrot: String,
-    pub sleep: Duration,
-    pub io_count: usize,
-    pub drive_workers: usize,
-    pub cache: Duration,
-}
-
-impl Config {
-    pub fn bitrot_scan_cycle(&self) -> Duration {
-        self.cache
-    }
-
-    pub fn get_workers(&self) -> usize {
-        self.drive_workers
-    }
-
-    pub fn update(&mut self, nopts: &Config) {
-        self.bitrot = nopts.bitrot.clone();
-        self.io_count = nopts.io_count;
-        self.sleep = nopts.sleep;
-        self.drive_workers = nopts.drive_workers;
-    }
-}
-
-const RUSTFS_BITROT_CYCLE_IN_MONTHS: u64 = 1;
-
-fn parse_bitrot_config(s: &str) -> Result<Duration> {
-    match parse_bool(s) {
-        Ok(enabled) => {
-            if enabled {
-                Ok(Duration::from_secs_f64(0.0))
-            } else {
-                Ok(Duration::from_secs_f64(-1.0))
-            }
-        }
-        Err(_) => {
-            if !s.ends_with("m") {
-                return Err(Error::other("unknown format"));
-            }
-
-            match s.trim_end_matches('m').parse::<u64>() {
-                Ok(months) => {
-                    if months < RUSTFS_BITROT_CYCLE_IN_MONTHS {
-                        return Err(Error::other(format!("minimum bitrot cycle is {RUSTFS_BITROT_CYCLE_IN_MONTHS} month(s)")));
-                    }
-
-                    Ok(Duration::from_secs(months * 30 * 24 * 60))
-                }
-                Err(err) => Err(Error::other(err)),
-            }
-        }
-    }
-}

crates/ecstore/src/config/mod.rs

@@ -16,7 +16,6 @@
 
 mod audit;
 pub mod com;
-#[allow(dead_code)]
 pub mod heal;
 mod notify;
 mod oidc;

crates/ecstore/src/core/pools.rs

@@ -1996,11 +1996,11 @@ impl PoolMeta {
         Ok(false)
     }
 
-    #[allow(dead_code)]
     pub fn validate(&self, pools: Vec<Arc<Sets>>) -> Result<bool> {
         struct PoolInfo {
             position: usize,
             completed: bool,
+            #[allow(dead_code, reason = "written but never read back (backlog#1823)")]
             decom_started: bool,
         }
 
@@ -4958,13 +4958,19 @@ fn is_disk_online_state(state: &str) -> bool {
 }
 
 #[deprecated(since = "0.1.0", note = "Use fallback_total_capacity_dedup instead")]
-#[allow(dead_code)]
+#[allow(
+    dead_code,
+    reason = "superseded by the replacement named in the comment at pools.rs:5071 (backlog#1823)"
+)]
 fn fallback_total_capacity(disks: &[rustfs_madmin::Disk]) -> usize {
     fallback_total_capacity_dedup(disks)
 }
 
 #[deprecated(since = "0.1.0", note = "Use fallback_free_capacity_dedup instead")]
-#[allow(dead_code)]
+#[allow(
+    dead_code,
+    reason = "superseded by the replacement named in the comment at pools.rs:5071 (backlog#1823)"
+)]
 fn fallback_free_capacity(disks: &[rustfs_madmin::Disk]) -> usize {
     fallback_free_capacity_dedup(disks)
 }

crates/ecstore/src/disk/local.rs

@@ -6562,7 +6562,7 @@ impl LocalDisk {
         Ok(f)
     }
 
-    #[allow(dead_code)]
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn get_metrics(&self) -> DiskMetrics {
         DiskMetrics::default()
     }

crates/ecstore/src/services/rebalance/types.rs

@@ -132,7 +132,6 @@ impl RebalanceStopPropagationRecord {
     }
 }
 
-#[allow(dead_code)]
 #[derive(Debug, Clone, Default)]
 pub struct DiskStat {
     pub total_space: u64,

crates/ecstore/src/services/tier/tier_config.rs

@@ -16,8 +16,16 @@ use serde::{Deserialize, Serialize};
 use std::{fmt::Display, io};
 use tracing::info;
 
+#[allow(
+    dead_code,
+    reason = "tier config wire version stamped by the parity constructors below (backlog#1823)"
+)]
 const C_TIER_CONFIG_VER: &str = "v1";
 
+#[allow(
+    dead_code,
+    reason = "tier-name validation message reached only from the parity constructors below (backlog#1823)"
+)]
 const ERR_TIER_NAME_EMPTY: &str = "remote tier name empty";
 const WASABI_US_EAST_ENDPOINT: &str = "https://s3.wasabisys.com";
 const WASABI_ALTERNATIVE_ENDPOINTS: &[(&str, &str)] = &[
@@ -264,7 +272,6 @@ impl Clone for TierConfig {
     }
 }
 
-#[allow(dead_code)]
 impl TierConfig {
     pub(crate) fn clone_with_credentials(&self) -> Self {
         Self {
@@ -284,6 +291,7 @@ impl TierConfig {
         }
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn endpoint(&self) -> String {
         match self.tier_type {
             TierType::S3 => self.s3.as_ref().map(|s| s.endpoint.clone()).unwrap_or_default(),
@@ -303,6 +311,7 @@ impl TierConfig {
         }
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn bucket(&self) -> String {
         match self.tier_type {
             TierType::S3 => self.s3.as_ref().map(|s| s.bucket.clone()).unwrap_or_default(),
@@ -322,6 +331,7 @@ impl TierConfig {
         }
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn prefix(&self) -> String {
         match self.tier_type {
             TierType::S3 => self.s3.as_ref().map(|s| s.prefix.clone()).unwrap_or_default(),
@@ -341,6 +351,7 @@ impl TierConfig {
         }
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn region(&self) -> String {
         match self.tier_type {
             TierType::S3 => self.s3.as_ref().map(|s| s.region.clone()).unwrap_or_default(),
@@ -457,7 +468,7 @@ impl TierWasabi {
 }
 
 impl TierS3 {
-    #[allow(dead_code)]
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn create<F>(
         name: &str,
         access_key: &str,
@@ -528,7 +539,7 @@ pub struct TierMinIO {
 }
 
 impl TierMinIO {
-    #[allow(dead_code)]
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn create<F>(
         name: &str,
         endpoint: &str,

crates/ecstore/src/services/tier/tier_gen.rs

@@ -14,7 +14,6 @@
 
 use crate::services::tier::tier::TierConfigMgr;
 
-#[allow(dead_code)]
 impl TierConfigMgr {
     pub fn msg_size(&self) -> usize {
         100

crates/ecstore/src/store/mod.rs

@@ -216,6 +216,16 @@ impl std::fmt::Debug for ECStore {
 /// These delegate to the process-global statics. No local state — the globals
 /// remain the single source of truth until the migration is complete.
 impl ECStore {
+    /// Every erasure set across all pools, pool-major order.
+    ///
+    /// Read-only queries that must consult each set's own copy of a
+    /// per-bucket object (e.g. the scanner's `.usage-cache.bin`) iterate
+    /// this instead of the hash-routed store path, which would always land
+    /// on one set (rustfs/backlog#1872).
+    pub fn all_set_disks(&self) -> Vec<Arc<crate::set_disk::SetDisks>> {
+        self.pools.iter().flat_map(|pool| pool.disk_set.iter().cloned()).collect()
+    }
+
     /// Get server configuration (delegates to global)
     pub fn get_server_config(&self) -> Option<Config> {
         runtime_sources::server_config()

crates/scanner/src/data_usage_define.rs

@@ -28,7 +28,8 @@ use rustfs_common::heal_channel::HealScanMode;
 use rustfs_config::ENV_SCANNER_CACHE_SAVE_TIMEOUT_SECS;
 pub use rustfs_data_usage::{
     AllTierStats, BucketTargetUsageInfo, BucketUsageInfo, DATA_USAGE_OBJECT_NAME, DATA_USAGE_OBSERVED_OBJECT_NAME,
-    DataUsageEntry, DataUsageHash, DataUsageHashMap, DataUsageInfo, LEGACY_DATA_USAGE_OBJECT_NAME, TierStats, hash_path,
+    DataUsageEntry, DataUsageHash, DataUsageHashMap, DataUsageInfo, LEGACY_DATA_USAGE_OBJECT_NAME, PrefixUsageEntry,
+    PrefixUsageQuery, PrefixUsageSummary, TierStats, hash_path, prefix_usage_in_cache,
 };
 use rustfs_utils::path::{SLASH_SEPARATOR, path_join_buf};
 use tokio::time::{Duration, Instant, sleep, timeout};
@@ -430,6 +431,13 @@ pub(crate) enum DataUsageCachePrepareOutcome {
 }
 
 impl DataUsageCache {
+    /// Prefix-level usage query over this (writer-side) cache; see
+    /// [`prefix_usage_in_cache`] for the semantics
+    /// (rustfs/backlog#1872).
+    pub fn prefix_usage(&self, bucket: &str, prefix: &str, max_entries: usize) -> Option<PrefixUsageQuery> {
+        prefix_usage_in_cache(&self.cache, bucket, prefix, max_entries)
+    }
+
     pub(crate) fn prepare_for_scan(
         &mut self,
         name: &str,

crates/scanner/src/lib.rs

@@ -53,6 +53,7 @@ use tokio_util::sync::CancellationToken;
 
 pub mod data_usage_define;
 pub mod error;
+pub mod prefix_usage;
 mod remote_scanner;
 pub mod runtime_config;
 pub mod scanner;
@@ -64,6 +65,7 @@ pub(crate) mod storage_api;
 
 pub use data_usage_define::*;
 pub use error::ScannerError;
+pub use prefix_usage::{BucketPrefixUsageResponse, bucket_prefix_usage, invalidate_prefix_usage_cache};
 pub use remote_scanner::{
     NS_SCANNER_MAX_REQUEST_BODY_SIZE, RemoteScannerAdmission, RemoteScannerRequest, admit_remote_scanner_request,
     claim_remote_scanner_request, decode_remote_scanner_request, preflight_remote_scanner_request,

crates/scanner/src/prefix_usage.rs

@@ -0,0 +1,349 @@
+// Copyright 2024 RustFS Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Prefix-level bucket usage for admin/console consumers (rustfs/backlog#1872,
+//! MinIO `loadPrefixUsageFromBackend` parity).
+//!
+//! The per-bucket, per-set `.usage-cache.bin` objects already hold a
+//! path-keyed prefix tree; this module reads every set's copy through that
+//! set's own object layer (the hash-routed store path would always land on
+//! one set), aggregates the overlapping trees, and serves the result from a
+//! bounded 30-second cache. Bucket writes poke the cache through the
+//! dirty-usage hook so a fresh scan is visible immediately.
+
+use crate::data_usage_define::{DATA_USAGE_CACHE_NAME, DataUsageCache};
+use crate::error::ScannerError;
+use crate::storage_api::owner::{
+    EcstoreSetDisks, EcstoreStore, ecstore_is_reserved_or_invalid_bucket, ecstore_resolve_object_store_handle,
+};
+use futures::future::join_all;
+use rustfs_data_usage::{PrefixUsageEntry, PrefixUsageSummary};
+use std::collections::HashMap;
+use std::sync::{Arc, Mutex};
+use std::time::{Duration, SystemTime};
+use tracing::{debug, warn};
+
+const LOG_COMPONENT_SCANNER: &str = "scanner";
+const LOG_SUBSYSTEM_PREFIX_USAGE: &str = "prefix_usage";
+const EVENT_PREFIX_USAGE_CACHE_STATE: &str = "prefix_usage_cache_state";
+
+/// How long a computed breakdown stays fresh. MinIO uses the same 30s for
+/// its prefix-usage cache; bucket writes additionally invalidate on the spot.
+const CACHE_TTL: Duration = Duration::from_secs(30);
+/// Hard entry cap for the result cache; exceeded, expired entries go first
+/// and the map clears rather than growing past the bound.
+const CACHE_MAX_ENTRIES: usize = 128;
+/// Per-set cache read budget. The underlying loader retries for up to a
+/// minute per attempt on backend errors — far too long for an admin GET, so
+/// a slow set degrades to "not reporting" instead of stalling the caller.
+const PER_SET_LOAD_TIMEOUT: Duration = Duration::from_secs(5);
+
+/// Aggregated prefix-usage answer across every erasure set.
+#[derive(Clone, Debug, PartialEq, serde::Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct BucketPrefixUsageResponse {
+    pub bucket: String,
+    pub prefix: String,
+    pub usage: PrefixUsageSummary,
+    /// Every reporting set's prefix entry was compacted: the aggregate is
+    /// valid, the sub-prefix breakdown is empty on disk.
+    pub compacted: bool,
+    /// The sub-prefix breakdown is incomplete: at least one reporting set
+    /// had the prefix compacted (or absent while others found it), so its
+    /// objects cannot be attributed to a sub-prefix.
+    pub sub_prefixes_partial: bool,
+    /// The breakdown exceeded the caller's entry limit; largest remain.
+    pub truncated: bool,
+    pub sub_prefixes: Vec<PrefixUsageEntry>,
+    /// Sets whose cache held this bucket and prefix.
+    pub sets_reporting: usize,
+    pub sets_total: usize,
+    /// Newest `last_update` across reporting sets, unix seconds.
+    pub last_update_unix_secs: Option<u64>,
+}
+
+#[derive(Clone)]
+struct CachedResponse {
+    computed_at: std::time::Instant,
+    response: Arc<BucketPrefixUsageResponse>,
+}
+
+/// Cache key: (lowercased bucket, normalized prefix, max entries).
+type PrefixUsageCacheKey = (String, String, usize);
+type PrefixUsageCacheMap = Option<HashMap<PrefixUsageCacheKey, CachedResponse>>;
+
+static PREFIX_USAGE_CACHE: Mutex<PrefixUsageCacheMap> = Mutex::new(None);
+
+/// Drop cached results for `bucket` (empty string clears everything). Wired
+/// into the dirty-usage recording path so a write makes the next prefix
+/// query recompute instead of serving up to `CACHE_TTL` seconds of stale
+/// numbers.
+pub fn invalidate_prefix_usage_cache(bucket: &str) {
+    let mut guard = PREFIX_USAGE_CACHE.lock().unwrap_or_else(|poison| poison.into_inner());
+    let Some(map) = guard.as_mut() else {
+        return;
+    };
+    if bucket.is_empty() {
+        map.clear();
+        return;
+    }
+    map.retain(|(cached_bucket, ..), _| !cached_bucket.eq_ignore_ascii_case(bucket));
+}
+
+/// Query prefix usage for `bucket` (arbitrary `prefix`, empty = whole
+/// bucket), merging every erasure set's own cache copy. `max_entries` bounds
+/// the sub-prefix rows (largest first).
+pub async fn bucket_prefix_usage(
+    bucket: &str,
+    prefix: &str,
+    max_entries: usize,
+) -> Result<BucketPrefixUsageResponse, ScannerError> {
+    if ecstore_is_reserved_or_invalid_bucket(bucket, true) {
+        return Err(ScannerError::Other(format!("invalid bucket name: {bucket}")));
+    }
+    let normalized_prefix = prefix.trim_matches('/').to_string();
+    let cache_key = (bucket.to_ascii_lowercase(), normalized_prefix.clone(), max_entries);
+    if let Some(response) = lookup_cached(&cache_key) {
+        return Ok((*response).clone());
+    }
+
+    let store = ecstore_resolve_object_store_handle()
+        .ok_or_else(|| ScannerError::Other("object store is not initialized".to_string()))?;
+    let response = Arc::new(compute_prefix_usage(store, bucket, &normalized_prefix, max_entries).await);
+    store_cached(cache_key, response.clone());
+    Ok((*response).clone())
+}
+
+async fn compute_prefix_usage(
+    store: Arc<EcstoreStore>,
+    bucket: &str,
+    prefix: &str,
+    max_entries: usize,
+) -> BucketPrefixUsageResponse {
+    let sets: Vec<Arc<EcstoreSetDisks>> = store.all_set_disks();
+    let sets_total = sets.len();
+    let cache_name = format!("{bucket}/{DATA_USAGE_CACHE_NAME}");
+
+    let per_set = join_all(sets.into_iter().map(|set| {
+        let cache_name = cache_name.clone();
+        async move {
+            let mut cache = DataUsageCache::default();
+            // A set that has never scanned this bucket (or cannot be read
+            // within the budget) reports nothing — the remaining sets still
+            // produce a usable, flagged answer.
+            let loaded = match tokio::time::timeout(PER_SET_LOAD_TIMEOUT, cache.load(set, &cache_name)).await {
+                Ok(Ok(())) => cache,
+                Ok(Err(err)) => {
+                    debug!(
+                        target: "rustfs::scanner::prefix_usage",
+                        event = EVENT_PREFIX_USAGE_CACHE_STATE,
+                        component = LOG_COMPONENT_SCANNER,
+                        subsystem = LOG_SUBSYSTEM_PREFIX_USAGE,
+                        bucket = %bucket,
+                        state = "set_load_failed",
+                        error = %err,
+                        "Prefix usage set cache load failed"
+                    );
+                    return None;
+                }
+                Err(_) => {
+                    warn!(
+                        target: "rustfs::scanner::prefix_usage",
+                        event = EVENT_PREFIX_USAGE_CACHE_STATE,
+                        component = LOG_COMPONENT_SCANNER,
+                        subsystem = LOG_SUBSYSTEM_PREFIX_USAGE,
+                        bucket = %bucket,
+                        state = "set_load_timeout",
+                        "Prefix usage set cache load timed out"
+                    );
+                    return None;
+                }
+            };
+            if loaded.info.name != bucket {
+                // Empty or stale-scoped cache: this set has no data for the bucket.
+                return None;
+            }
+            let last_update = loaded.info.last_update;
+            let query = loaded.prefix_usage(bucket, prefix, max_entries);
+            Some((query, last_update))
+        }
+    }))
+    .await;
+
+    let mut usage = PrefixUsageSummary::default();
+    let mut sub_prefix_map: HashMap<String, PrefixUsageSummary> = HashMap::new();
+    let mut sets_reporting = 0usize;
+    let mut reporting_but_absent = 0usize;
+    let mut any_compacted = false;
+    let mut all_compacted = true;
+    let mut truncated = false;
+    let mut last_update: Option<SystemTime> = None;
+
+    for (query, set_last_update) in per_set.into_iter().flatten() {
+        // last_update counts every set that has scanned the bucket, even
+        // when the prefix itself is absent on that set.
+        if let Some(set_last_update) = set_last_update
+            && last_update.map(|current| set_last_update > current).unwrap_or(true)
+        {
+            last_update = Some(set_last_update);
+        }
+        let Some(query) = query else {
+            // The set knows the bucket but not this prefix: legitimate when
+            // the prefix's objects all hash to other sets, but it means the
+            // breakdown below cannot attribute that set's (zero) objects.
+            reporting_but_absent += 1;
+            continue;
+        };
+        sets_reporting += 1;
+        usage.merge(&query.usage);
+        if query.compacted {
+            any_compacted = true;
+        } else {
+            all_compacted = false;
+        }
+        truncated |= query.truncated;
+        for entry in query.sub_prefixes {
+            sub_prefix_map.entry(entry.prefix).or_default().merge(&entry.usage);
+        }
+    }
+
+    let mut sub_prefixes: Vec<PrefixUsageEntry> = sub_prefix_map
+        .into_iter()
+        .map(|(prefix, usage)| PrefixUsageEntry { prefix, usage })
+        .collect();
+    sub_prefixes.sort_by(|left, right| {
+        right
+            .usage
+            .size
+            .cmp(&left.usage.size)
+            .then_with(|| left.prefix.cmp(&right.prefix))
+    });
+    // Merged rows can exceed max_entries only when per-set truncation
+    // already flagged; enforce the caller bound on the merged view too.
+    if sub_prefixes.len() > max_entries {
+        truncated = true;
+        sub_prefixes.truncate(max_entries);
+    }
+
+    let found = sets_reporting > 0;
+    BucketPrefixUsageResponse {
+        bucket: bucket.to_string(),
+        prefix: prefix.to_string(),
+        usage,
+        compacted: found && all_compacted,
+        sub_prefixes_partial: any_compacted || reporting_but_absent > 0,
+        truncated,
+        sub_prefixes,
+        sets_reporting,
+        sets_total,
+        last_update_unix_secs: last_update
+            .and_then(|time| time.duration_since(SystemTime::UNIX_EPOCH).ok())
+            .map(|dur| dur.as_secs()),
+    }
+}
+
+fn lookup_cached(key: &(String, String, usize)) -> Option<Arc<BucketPrefixUsageResponse>> {
+    let mut guard = PREFIX_USAGE_CACHE.lock().unwrap_or_else(|poison| poison.into_inner());
+    let map = guard.as_mut()?;
+    let cached = map.get(key)?;
+    if cached.computed_at.elapsed() > CACHE_TTL {
+        map.remove(key);
+        return None;
+    }
+    Some(cached.response.clone())
+}
+
+fn store_cached(key: (String, String, usize), response: Arc<BucketPrefixUsageResponse>) {
+    let mut guard = PREFIX_USAGE_CACHE.lock().unwrap_or_else(|poison| poison.into_inner());
+    let map = guard.get_or_insert_with(HashMap::new);
+    // Bound the cache: drop expired entries first, and if the cap is still
+    // exceeded clear wholesale — the next queries recompute in milliseconds.
+    if map.len() >= CACHE_MAX_ENTRIES {
+        map.retain(|_, cached| cached.computed_at.elapsed() <= CACHE_TTL);
+        if map.len() >= CACHE_MAX_ENTRIES {
+            map.clear();
+        }
+    }
+    map.insert(
+        key,
+        CachedResponse {
+            computed_at: std::time::Instant::now(),
+            response,
+        },
+    );
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{CACHE_MAX_ENTRIES, PREFIX_USAGE_CACHE, invalidate_prefix_usage_cache, store_cached};
+    use rustfs_data_usage::PrefixUsageSummary;
+
+    fn response(bucket: &str) -> super::BucketPrefixUsageResponse {
+        super::BucketPrefixUsageResponse {
+            bucket: bucket.to_string(),
+            prefix: String::new(),
+            usage: PrefixUsageSummary::default(),
+            compacted: false,
+            sub_prefixes_partial: false,
+            truncated: false,
+            sub_prefixes: Vec::new(),
+            sets_reporting: 1,
+            sets_total: 1,
+            last_update_unix_secs: None,
+        }
+    }
+
+    fn seed(bucket: &str, prefix: &str) {
+        store_cached(
+            (bucket.to_ascii_lowercase(), prefix.to_string(), 10),
+            std::sync::Arc::new(response(bucket)),
+        );
+    }
+
+    fn contains(bucket: &str, prefix: &str) -> bool {
+        PREFIX_USAGE_CACHE
+            .lock()
+            .unwrap_or_else(|poison| poison.into_inner())
+            .as_ref()
+            .is_some_and(|map| map.contains_key(&(bucket.to_ascii_lowercase(), prefix.to_string(), 10)))
+    }
+
+    /// All cache tests run inside one test to keep the process-global map
+    /// free of cross-test ordering (the flake class this module avoids).
+    #[test]
+    fn invalidation_scopes_to_bucket_and_cache_stays_bounded() {
+        invalidate_prefix_usage_cache("");
+        seed("alpha", "x");
+        seed("beta", "y");
+
+        // Case-insensitive bucket scoping.
+        invalidate_prefix_usage_cache("ALPHA");
+        assert!(!contains("alpha", "x"));
+        assert!(contains("beta", "y"));
+
+        // Wholesale clear.
+        invalidate_prefix_usage_cache("");
+        assert!(!contains("beta", "y"));
+
+        // Hard cap: overflow clears rather than grows.
+        for index in 0..=(CACHE_MAX_ENTRIES / 2) {
+            let bucket = format!("cap-bucket-{index}");
+            seed(&bucket, "a");
+            seed(&bucket, "b");
+        }
+        let guard = PREFIX_USAGE_CACHE.lock().unwrap_or_else(|poison| poison.into_inner());
+        let map = guard.as_ref().expect("seeded");
+        assert!(map.len() <= CACHE_MAX_ENTRIES, "cache must stay bounded, got {}", map.len());
+    }
+}

crates/scanner/src/scanner_io.rs

@@ -231,6 +231,10 @@ pub fn record_dirty_usage_bucket(bucket: &str) {
         dirty_buckets.len()
     };
     global_metrics().record_scanner_dirty_usage_pending(usize_to_u64_saturated(pending_buckets));
+    // A write invalidates this bucket's prefix-usage answers on the spot so
+    // admin/console consumers never ride the full TTL after a change
+    // (rustfs/backlog#1872).
+    crate::prefix_usage::invalidate_prefix_usage_cache(bucket);
     DIRTY_USAGE_BUCKET_NOTIFY.notify_one();
 }
 

rustfs/src/admin/handlers/mod.rs

@@ -64,6 +64,7 @@ mod target_descriptor;
 pub mod tier;
 pub mod tls_debug;
 pub mod trace;
+pub mod usage_prefix;
 pub mod user;
 pub mod user_iam;
 pub mod user_lifecycle;

rustfs/src/admin/handlers/site_replication.rs

@@ -6023,7 +6023,10 @@ fn edit_generation_wall_clock() -> u64 {
 /// node's clock behind the clock that fed the previous lifetime) mints
 /// below the stale mark and the origin stays fenced — but only until real
 /// time passes the previous lifetime's last allocation, because every later
-/// allocation takes the wall-clock floor again. Bounded by the skew,
+/// allocation takes the wall-clock floor again (and never longer than
+/// [`PEER_EDIT_FENCE_STALENESS_WINDOW_NANOS`]: a regression past the window
+/// leaves the mark implausibly distant and the origin runs unfenced
+/// immediately). Bounded by the skew,
 /// self-healing, and no rollback window beyond the plain counter's: a
 /// delivery applies only at or above the receiver's mark, so the one
 /// cross-lifetime interleaving that can apply stale content — a
@@ -6063,6 +6066,52 @@ fn peer_edit_fence(queries: &HashMap<String, String>) -> Option<(String, u64)> {
     Some((origin.clone(), generation))
 }
 
+/// How far below the recorded high-water mark a delivery may sit and still
+/// be fenced as stale. The distance a GENUINE superseded delivery can trail
+/// its origin's mark is small: retransmissions re-run the sender flow and
+/// mint a fresh generation (the retry queue keys on the bare path and never
+/// replays a fenced URL), so only an in-flight straggler of the losing
+/// fan-out race trails the mark, by delivery latency — minutes at the
+/// outside. A mark further above than this window cannot be explained by
+/// any genuine race, only by a forged fence (the shared service account
+/// lets any peer stamp any origin) or by a persisted clock excursion the
+/// origin has since left behind — and fencing on it would silently drop the
+/// origin's real edits, so the stale check ignores it instead.
+const PEER_EDIT_FENCE_STALENESS_WINDOW_NANOS: u64 = 24 * 60 * 60 * 1_000_000_000;
+
+/// Whether an incoming fence may be honoured, as far as this site can vouch
+/// for it. The sender's identity is unverifiable (shared service account),
+/// so the check runs over what the receiving state knows: the claimed origin
+/// must be a site this state currently replicates with — the same membership
+/// rule the load-time mark pruning applies, so every mark recorded behind
+/// this check is one a reload would keep — and not this site itself, which
+/// never delivers edits to itself. The caller IGNORES an inadmissible fence
+/// rather than failing the request: the delivery applies exactly as an
+/// unstamped (pre-fence) delivery would, no high-water mark is read or
+/// written, and the worst a forged fence achieves is forfeiting an ordering
+/// guarantee its sender was never owed. The generation itself is NOT
+/// bounded here: a genuine origin whose hybrid clock persisted a wall-clock
+/// excursion allocates arbitrarily far in the future, and refusing to
+/// record its marks would strip the ordering fence from exactly the
+/// deliveries that still race — the staleness window on the read side is
+/// what defuses forged marks instead.
+fn peer_edit_fence_is_admissible(state: &SiteReplicationState, local_deployment_id: &str, fence: &(String, u64)) -> bool {
+    let (origin, generation) = fence;
+    if origin != local_deployment_id && state.peers.contains_key(origin) {
+        return true;
+    }
+    warn!(
+        event = EVENT_ADMIN_SITE_REPLICATION_STATE,
+        component = LOG_COMPONENT_ADMIN,
+        subsystem = LOG_SUBSYSTEM_SITE_REPLICATION,
+        result = "fence_origin_not_a_remote_peer",
+        origin = %origin,
+        generation = *generation,
+        "ignoring inadmissible peer-edit fence"
+    );
+    false
+}
+
 /// True when a strictly newer edit from the same origin site already landed
 /// here. No lock on the sending side can order deliveries issued by two
 /// nodes of that site, so ordering is decided here, on the generation the
@@ -6070,11 +6119,42 @@ fn peer_edit_fence(queries: &HashMap<String, String>) -> Option<(String, u64)> {
 /// stale: one edit legitimately fans out several deliveries under a single
 /// generation (the ILM-expiry edit sends every peer's record), and a replay of
 /// an applied delivery re-applies the same edit idempotently.
+///
+/// A mark more than [`PEER_EDIT_FENCE_STALENESS_WINDOW_NANOS`] above the
+/// delivery is implausible and does NOT fence: the shared service account
+/// means any peer can stamp any origin, so a forged `u64::MAX`-scale mark
+/// would otherwise silently swallow the origin's genuine edits for good.
+/// Bounding the fence by distance instead of by an absolute ceiling keeps
+/// ordering intact wherever the origin's clock actually operates — two
+/// racing deliveries trail each other by seconds whether the hybrid clock
+/// tracks wall time or persists a long-gone excursion far ahead of it —
+/// while a mark no genuine race can explain merely downgrades the origin to
+/// unfenced (pre-fence) delivery instead of dropping its edits. (One genuine
+/// shape does land out here: a plain-counter straggler arriving after its
+/// origin's first hybrid-clock edit. It gets the same downgrade — applied
+/// unfenced — once, at upgrade time; fencing it instead would silence the
+/// mirror case, a hybrid-clock origin downgraded back to the plain counter.)
 fn peer_edit_delivery_is_stale(state: &SiteReplicationState, origin: &str, generation: u64) -> bool {
-    state
-        .applied_edit_generations
-        .get(origin)
-        .is_some_and(|applied| *applied > generation)
+    let Some(applied) = state.applied_edit_generations.get(origin) else {
+        return false;
+    };
+    if *applied <= generation {
+        return false;
+    }
+    if *applied - generation > PEER_EDIT_FENCE_STALENESS_WINDOW_NANOS {
+        warn!(
+            event = EVENT_ADMIN_SITE_REPLICATION_STATE,
+            component = LOG_COMPONENT_ADMIN,
+            subsystem = LOG_SUBSYSTEM_SITE_REPLICATION,
+            result = "fence_mark_beyond_staleness_window",
+            origin,
+            generation,
+            applied_mark = *applied,
+            "ignoring implausibly distant peer-edit high-water mark"
+        );
+        return false;
+    }
+    true
 }
 
 fn record_applied_peer_edit_generation(state: &mut SiteReplicationState, origin: &str, generation: u64) {
@@ -10698,6 +10778,11 @@ impl Operation for SRPeerEditHandler {
         let outcome = update_site_replication_state_when_changed(move |state| {
             let mut incoming = incoming;
             let local_peer = local_peer_at_endpoint(commit_endpoint, state);
+            // The fence is self-reported — the shared service account means
+            // the sender cannot be identified — so it is honoured only after
+            // the admissibility check, against the same state it will gate.
+            let commit_fence =
+                commit_fence.filter(|fence| peer_edit_fence_is_admissible(state, &local_peer.deployment_id, fence));
             // Ordering fence: the sending site allocates the generation under
             // its state-object lock, so a delivery that lost the race carries
             // a generation this site has already passed. Applying it would
@@ -13393,6 +13478,15 @@ mod tests {
             handler_block.contains("record_applied_peer_edit_generation(state, origin, *generation);"),
             "SRPeerEditHandler must record the applied generation so later stale deliveries are recognised"
         );
+        // Fence hardening: origin and generation are self-reported by a
+        // caller the shared service account cannot identify, so the handler
+        // must pass the fence through the admissibility check — against the
+        // same state the fence gates, i.e. inside the transaction — before
+        // reading or raising any high-water mark.
+        assert!(
+            handler_block.contains(".filter(|fence| peer_edit_fence_is_admissible(state, &local_peer.deployment_id, fence))"),
+            "SRPeerEditHandler must admit a fence only through peer_edit_fence_is_admissible inside the state transaction"
+        );
         // P1-15 PR2: both halves of the fence and the edit they fence share
         // ONE transaction. Checking the fence against a state read outside the
         // lock would let the check pass on one snapshot and the write land on
@@ -14769,6 +14863,121 @@ mod tests {
         assert!(peer_edit_delivery_is_stale(&state, origin, generation - 1));
     }
 
+    /// A fence is self-reported: every site authenticates peer traffic with
+    /// the same site-replicator credential, so a compromised peer can stamp
+    /// ANY origin with ANY generation. An origin the receiver does not
+    /// replicate with — or the receiver itself — is ignored and plants no
+    /// mark; a mark a compromised peer plants for a CURRENT origin cannot
+    /// silence that origin, because the staleness window refuses to fence on
+    /// a mark implausibly far above the genuine deliveries.
+    #[test]
+    fn forged_peer_edit_fences_cannot_poison_the_high_water_marks() {
+        let mut state = SiteReplicationState {
+            peers: BTreeMap::from([
+                (
+                    "site-local".to_string(),
+                    PeerInfo {
+                        deployment_id: "site-local".to_string(),
+                        ..peer("local", "https://local.example:9000")
+                    },
+                ),
+                (
+                    "site-victim".to_string(),
+                    PeerInfo {
+                        deployment_id: "site-victim".to_string(),
+                        ..peer("victim", "https://victim.example:9000")
+                    },
+                ),
+            ]),
+            ..Default::default()
+        };
+        // An origin outside the current membership is refused outright...
+        let unknown = ("site-unknown".to_string(), 4u64);
+        assert!(!peer_edit_fence_is_admissible(&state, "site-local", &unknown));
+
+        // No site delivers edits to itself: a fence claiming the receiver as
+        // its origin is forged by construction, current peer or not.
+        let own = ("site-local".to_string(), 4u64);
+        assert!(!peer_edit_fence_is_admissible(&state, "site-local", &own));
+
+        // A current remote peer's fence is admitted and works end to end.
+        let genuine = ("site-victim".to_string(), 1u64);
+        assert!(peer_edit_fence_is_admissible(&state, "site-local", &genuine));
+        assert!(!peer_edit_delivery_is_stale(&state, &genuine.0, genuine.1));
+        record_applied_peer_edit_generation(&mut state, &genuine.0, genuine.1);
+        assert_eq!(state.applied_edit_generations.get("site-victim"), Some(&1));
+
+        // A forged u64::MAX-scale mark CAN be recorded — the shared service
+        // account means the receiver cannot tell the stamp was forged — but
+        // it is inert: the victim's genuine hybrid-clock deliveries sit far
+        // more than the staleness window below it, so they keep applying
+        // instead of being silently acked-and-dropped.
+        record_applied_peer_edit_generation(&mut state, "site-victim", u64::MAX);
+        assert!(!peer_edit_delivery_is_stale(&state, "site-victim", edit_generation_wall_clock()));
+    }
+
+    /// The staleness window bounds the fence by DISTANCE from the mark, not
+    /// by an absolute clock ceiling, so ordering must hold wherever the
+    /// origin's hybrid clock actually operates. The regression that matters:
+    /// a temporary wall-clock excursion far in the future is persisted by
+    /// `next_peer_edit_generation` (`max(now, prev + 1)` never comes back
+    /// down), and two later edits g+1 then g can arrive in reverse order —
+    /// g must still be fenced, even though both generations dwarf the
+    /// receiver's clock. Conversely a mark further above a delivery than any
+    /// genuine race can explain must not fence it.
+    #[test]
+    fn peer_edit_fence_orders_a_persisted_future_clock_and_defuses_distant_marks() {
+        let mut state = SiteReplicationState {
+            peers: BTreeMap::from([(
+                "site-origin".to_string(),
+                PeerInfo {
+                    deployment_id: "site-origin".to_string(),
+                    ..peer("origin", "https://origin.example:9000")
+                },
+            )]),
+            ..Default::default()
+        };
+
+        // The origin's clock once jumped ten years ahead; the hybrid clock
+        // keeps allocating from there long after the clock was corrected.
+        let excursion = edit_generation_wall_clock() + 10 * 365 * 24 * 60 * 60 * 1_000_000_000;
+        let fence = ("site-origin".to_string(), excursion + 1);
+        assert!(peer_edit_fence_is_admissible(&state, "site-local", &fence));
+        record_applied_peer_edit_generation(&mut state, &fence.0, fence.1);
+
+        // The reverse delivery of the race: g arrives after g+1 landed.
+        // Without the fence it would commit last and roll g+1 back.
+        assert!(peer_edit_delivery_is_stale(&state, "site-origin", excursion));
+        // Equal generation (same edit's fan-out or a replay) still applies,
+        // as does the next edit.
+        assert!(!peer_edit_delivery_is_stale(&state, "site-origin", excursion + 1));
+        assert!(!peer_edit_delivery_is_stale(&state, "site-origin", excursion + 2));
+
+        // The window's exact boundary: a delivery trailing the mark by the
+        // full window is still fenced; one nanosecond further is not — that
+        // distance is no longer explicable by a genuine race, only by a
+        // forged mark or an excursion the origin has left behind.
+        let mark = fence.1;
+        // A straggler trailing by a concrete hour must still be fenced —
+        // pins the window's real magnitude, not just its symbolic boundary.
+        assert!(peer_edit_delivery_is_stale(&state, "site-origin", mark - 60 * 60 * 1_000_000_000));
+        assert!(peer_edit_delivery_is_stale(
+            &state,
+            "site-origin",
+            mark - PEER_EDIT_FENCE_STALENESS_WINDOW_NANOS
+        ));
+        assert!(!peer_edit_delivery_is_stale(
+            &state,
+            "site-origin",
+            mark - PEER_EDIT_FENCE_STALENESS_WINDOW_NANOS - 1
+        ));
+
+        // A pre-hybrid plain-counter origin trails such a mark by eons: it
+        // is not fenced (the rc.2-era downgrade case), it just runs
+        // unfenced until its counter regime catches up.
+        assert!(!peer_edit_delivery_is_stale(&state, "site-origin", 3));
+    }
+
     /// P1-15 review follow-up: a site that leaves the mesh drops below two
     /// peers, which clears its state object and restarts its generation
     /// counter at zero. A mark left over from its previous membership would

rustfs/src/admin/handlers/system.rs

@@ -1158,10 +1158,10 @@ impl Operation for RuntimeCapabilitiesHandler {
     }
 }
 
-/// Authorization gate for GET datausageinfo: any-of the dedicated admin action
-/// OR the bucket listing action. Pinned by a unit test so the gate cannot
-/// silently narrow or widen (rustfs/backlog#1306).
-fn data_usage_info_gate_actions() -> Vec<Action> {
+/// Authorization gate for GET datausageinfo (and prefix usage): any-of the
+/// dedicated admin action OR the bucket listing action. Pinned by a unit test
+/// so the gate cannot silently narrow or widen (rustfs/backlog#1306).
+pub(crate) fn data_usage_info_gate_actions() -> Vec<Action> {
     vec![
         Action::AdminAction(AdminAction::DataUsageInfoAdminAction),
         Action::S3Action(S3Action::ListBucketAction),

rustfs/src/admin/handlers/usage_prefix.rs

@@ -0,0 +1,142 @@
+// Copyright 2024 RustFS Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Prefix-level bucket usage admin handler (rustfs/backlog#1872).
+//!
+//! `GET /rustfs/admin/v3/usage/{bucket}?prefix=&max-entries=` answers
+//! "what does this bucket / this prefix hold" from the scanner's per-set
+//! usage caches, with a one-level sub-prefix breakdown — the data console
+//! buckets view MinIO serves from `loadPrefixUsageFromBackend`.
+
+use crate::admin::auth::validate_admin_request;
+use crate::admin::handlers::system::data_usage_info_gate_actions;
+use crate::admin::router::{AdminOperation, Operation, S3Router};
+use crate::auth::{check_key_valid, get_session_token};
+use crate::server::{ADMIN_PREFIX, RemoteAddr};
+use http::{HeaderMap, HeaderValue, StatusCode};
+use hyper::Method;
+use matchit::Params;
+use s3s::header::CONTENT_TYPE;
+use s3s::{Body, S3Error, S3ErrorCode, S3Request, S3Response, S3Result, s3_error};
+
+const JSON_CONTENT_TYPE: &str = "application/json";
+const DEFAULT_MAX_ENTRIES: usize = 1000;
+const MAX_ENTRIES_LIMIT: usize = 10_000;
+
+pub struct BucketPrefixUsageHandler {}
+
+pub fn register_usage_prefix_route(r: &mut S3Router<AdminOperation>) -> std::io::Result<()> {
+    r.insert(
+        Method::GET,
+        format!("{}{}", ADMIN_PREFIX, "/v3/usage/{bucket}").as_str(),
+        AdminOperation(&BucketPrefixUsageHandler {}),
+    )?;
+    Ok(())
+}
+
+/// Parse `prefix` and `max-entries` from the query string. Unknown keys are
+/// rejected so a typo'd parameter cannot silently change the answer's shape.
+fn parse_usage_prefix_query(query: Option<&str>) -> S3Result<(String, usize)> {
+    let mut prefix: Option<String> = None;
+    let mut max_entries: Option<usize> = None;
+    for (key, value) in url::form_urlencoded::parse(query.unwrap_or_default().as_bytes()) {
+        match key.as_ref() {
+            "prefix" => prefix = Some(value.into_owned()),
+            "max-entries" => {
+                max_entries = Some(
+                    value
+                        .parse::<usize>()
+                        .map_err(|_| s3_error!(InvalidArgument, "max-entries must be a positive integer"))?,
+                );
+            }
+            other => return Err(s3_error!(InvalidArgument, "unknown query parameter: {other}")),
+        }
+    }
+    let max_entries = max_entries.unwrap_or(DEFAULT_MAX_ENTRIES).clamp(1, MAX_ENTRIES_LIMIT);
+    Ok((prefix.unwrap_or_default(), max_entries))
+}
+
+#[async_trait::async_trait]
+impl Operation for BucketPrefixUsageHandler {
+    async fn call(&self, req: S3Request<Body>, params: Params<'_, '_>) -> S3Result<S3Response<(StatusCode, Body)>> {
+        let Some(input_cred) = req.credentials else {
+            return Err(s3_error!(InvalidRequest, "get cred failed"));
+        };
+
+        let (cred, owner) =
+            check_key_valid(get_session_token(&req.uri, &req.headers).unwrap_or_default(), &input_cred.access_key).await?;
+
+        let remote_addr = req.extensions.get::<Option<RemoteAddr>>().and_then(|opt| opt.map(|a| a.0));
+        validate_admin_request(&req.headers, &cred, owner, false, data_usage_info_gate_actions(), remote_addr).await?;
+
+        let bucket = params.get("bucket").unwrap_or_default().to_string();
+        if bucket.is_empty() {
+            return Err(s3_error!(InvalidRequest, "bucket path parameter is required"));
+        }
+        let (prefix, max_entries) = parse_usage_prefix_query(req.uri.query())?;
+
+        // Authorization is bucket-scoped by the same any-of gate as the
+        // datausageinfo route; the bucket name itself is validated by the
+        // scanner layer, which rejects reserved/invalid names.
+        let response = rustfs_scanner::bucket_prefix_usage(&bucket, &prefix, max_entries)
+            .await
+            .map_err(|err| s3_error!(InvalidArgument, "{}", err))?;
+
+        let data = serde_json::to_vec(&response)
+            .map_err(|_| S3Error::with_message(S3ErrorCode::InternalError, "parse prefix usage failed"))?;
+        let mut header = HeaderMap::new();
+        header.insert(CONTENT_TYPE, HeaderValue::from_static(JSON_CONTENT_TYPE));
+
+        Ok(S3Response::with_headers((StatusCode::OK, Body::from(data)), header))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{DEFAULT_MAX_ENTRIES, MAX_ENTRIES_LIMIT, parse_usage_prefix_query};
+    use s3s::S3Error;
+
+    fn query(raw: &str) -> Result<(String, usize), S3Error> {
+        parse_usage_prefix_query(Some(raw))
+    }
+
+    #[test]
+    fn defaults_apply_when_no_query_is_given() {
+        assert_eq!(parse_usage_prefix_query(None).unwrap(), (String::new(), DEFAULT_MAX_ENTRIES));
+        assert_eq!(query("").unwrap(), (String::new(), DEFAULT_MAX_ENTRIES));
+    }
+
+    #[test]
+    fn prefix_round_trips_url_encoded_characters() {
+        let (prefix, _) = query("prefix=pre%2Ffix%20name").unwrap();
+        assert_eq!(prefix, "pre/fix name");
+    }
+
+    #[test]
+    fn max_entries_parses_and_clamps_to_documented_bounds() {
+        assert_eq!(query("max-entries=5").unwrap().1, 5);
+        assert_eq!(query("max-entries=0").unwrap().1, 1, "zero must clamp up, not mean unlimited");
+        assert_eq!(query("max-entries=99999999").unwrap().1, MAX_ENTRIES_LIMIT);
+        assert!(query("max-entries=-3").is_err());
+        assert!(query("max-entries=abc").is_err());
+    }
+
+    #[test]
+    fn unknown_parameters_are_rejected_not_ignored() {
+        assert!(
+            query("prefixes=x").is_err(),
+            "a typo'd parameter must fail the request, not widen the query"
+        );
+    }
+}

rustfs/src/admin/mod.rs

@@ -40,7 +40,8 @@ use handlers::{
     audit, batch_job, bucket_meta, cluster_snapshot, config_admin, diagnostics, durability as durability_handler, extensions,
     heal, health, idp_compat, ilm_transition, inspect_archive, kms, module_switch, object_data_cache, object_zip_download, oidc,
     plugins_catalog, plugins_instances, pools, profile_admin, quota as quota_handler, rebalance,
-    replication as replication_handler, scanner, site_replication, sts, system, table_catalog, tier, tls_debug, user,
+    replication as replication_handler, scanner, site_replication, sts, system, table_catalog, tier, tls_debug, usage_prefix,
+    user,
 };
 use router::{AdminOperation, S3Router};
 use s3s::route::S3Route;
@@ -80,6 +81,7 @@ fn register_admin_routes(r: &mut S3Router<AdminOperation>) -> std::io::Result<()
     bucket_meta::register_bucket_meta_route(r)?;
     config_admin::register_config_route(r)?;
     scanner::register_scanner_route(r)?;
+    usage_prefix::register_usage_prefix_route(r)?;
     ilm_transition::register_ilm_transition_route(r)?;
     object_data_cache::register_object_data_cache_route(r)?;
     audit::register_audit_target_route(r)?;

rustfs/src/admin/route_policy.rs

@@ -1558,6 +1558,11 @@ pub const DEFERRED_ADMIN_ROUTE_POLICIES: &[DeferredAdminRoutePolicy] = &[
         "/rustfs/admin/v3/datausageinfo",
         DeferredRoutePolicyReason::MultipleActions,
     ),
+    deferred(
+        HttpMethod::Get,
+        "/rustfs/admin/v3/usage/{bucket}",
+        DeferredRoutePolicyReason::MultipleActions,
+    ),
     deferred(
         HttpMethod::Post,
         "/rustfs/admin/v3/object-zip-downloads",

rustfs/src/admin/route_registration_test.rs

@@ -172,6 +172,7 @@ fn expected_admin_route_matrix() -> Vec<RouteMatrixEntry> {
         admin_route(Method::POST, "/v4/inspect/archive"),
         admin_route(Method::GET, "/v3/storageinfo"),
         admin_route(Method::GET, "/v3/datausageinfo"),
+        admin_route_sample(Method::GET, "/v3/usage/{bucket}", "/v3/usage/test-bucket"),
         admin_route(Method::GET, "/v3/metrics"),
         admin_route(Method::GET, "/v3/object-data-cache/stats"),
         admin_route(Method::POST, "/v3/object-data-cache/flush"),