test(e2e): add distributed cluster regression coverage (#7158)

* test(e2e): add distributed 4x4 validation

* test(e2e): prove operations overlap data movement

---------

Co-authored-by: Zhengchao An <anzhengchao@gmail.com>

crates/e2e_test/src/distributed/concurrent_data_movement_test.rs

@@ -0,0 +1,74 @@
+// Copyright 2026 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/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.
+
+use super::harness::{
+    DECOMMISSION_POOL_ID, DistCluster, DistLayout, TestResult, assert_inventory, decommission_running_with_progress,
+    decommission_status_json, payload_for, put_inventory_retrying, retrying_get_equals, retrying_put, start_decommission,
+    unique_bucket, wait_for_decommission_complete, wait_for_decommission_running_with_progress,
+};
+use crate::common::init_logging;
+use std::sync::Arc;
+use std::time::Duration;
+use tokio::sync::Barrier;
+
+#[tokio::test]
+async fn concurrent_puts_during_decommission_do_not_lose_baseline_or_new_objects() -> TestResult {
+    init_logging();
+    let mut dist = DistCluster::start(DistLayout::SingleNodeFourDrive).await?;
+    let bucket = unique_bucket("concdecom");
+    dist.create_bucket(&bucket).await?;
+    let baseline_client = dist.client(0)?;
+    let inventory = put_inventory_retrying(&baseline_client, &bucket, 96, 256 * 1024, Duration::from_secs(30)).await?;
+    dist.expand_to_four_pools().await?;
+
+    start_decommission(&dist.cluster, DECOMMISSION_POOL_ID).await?;
+
+    let clients = Arc::new(dist.clients()?);
+    let barrier = Arc::new(Barrier::new(17));
+    let mut handles = Vec::new();
+    for idx in 0..16 {
+        let clients = clients.clone();
+        let barrier = barrier.clone();
+        let bucket = bucket.clone();
+        handles.push(tokio::spawn(async move {
+            barrier.wait().await;
+            let client = &clients[idx % clients.len()];
+            let key = format!("live/{idx:02}.bin");
+            let body = payload_for(&key, 8 * 1024);
+            retrying_put(client, &bucket, &key, body.clone(), Duration::from_secs(45)).await?;
+            Ok::<_, Box<dyn std::error::Error + Send + Sync>>((key, body))
+        }));
+    }
+
+    wait_for_decommission_running_with_progress(&dist.cluster, DECOMMISSION_POOL_ID, Duration::from_secs(30)).await?;
+    barrier.wait().await;
+
+    let mut live_objects = Vec::new();
+    for handle in handles {
+        live_objects.push(handle.await??);
+    }
+    let status = decommission_status_json(&dist.cluster).await?;
+    if !decommission_running_with_progress(&status, DECOMMISSION_POOL_ID)? {
+        return Err(format!("decommission did not remain active across concurrent PUTs: {status}").into());
+    }
+
+    wait_for_decommission_complete(&dist.cluster, DECOMMISSION_POOL_ID, Duration::from_secs(180)).await?;
+
+    let checker = dist.client(2)?;
+    assert_inventory(&checker, &bucket, &inventory).await?;
+    for (key, body) in live_objects {
+        retrying_get_equals(&checker, &bucket, &key, &body, Duration::from_secs(30)).await?;
+    }
+    Ok(())
+}