statvfs 统计挂载点选错：容器里只写 4 MiB 却上报「已用 7.6 TiB」，卷 89% 满仍不触发背压

cd scenario/2026-09-25-0800

docker compose up -d --build
docker compose ps -a
docker compose logs client

空卷: 上报 used_bytes=7374969933824 真实=0 偏差=7374969933824
写 4MiB: 上报增量=4272128 真实增量=4194304
填到水位以上: 上报 used_ratio=0.112465 卷自身占用率=686926.1% under_pressure=False 卷真实用量=843055104
高压下写 1MiB: ok=True written=1048576 errors=[]
RESULT: BAD

docker compose exec -T node bash -lc '/bin/bash /srv/ops/verify.sh'
# PASS=3 FAIL=5
# RESULT: BAD

docker compose exec -T node python3 -c "
import os
rows=[]
for line in open('/proc/self/mountinfo'):
    p=line.split()
    try: sep=p.index('-')
    except ValueError: continue
    mp=p[4].replace('\\\\040',' ')
    try:
        st=os.statvfs(mp)
        rows.append((mp,p[sep+1],st.f_blocks*st.f_frsize-st.f_bfree*st.f_frsize,st.f_blocks*st.f_frsize))
    except OSError: pass
rows.sort(key=lambda r:-r[2])
for mp,fs,u,t in rows[:5]: print(f'{mp:22} {fs:9} used={u/2**30:>9.2f}GB total={t/2**30:>10.2f}GB')
"

/etc/resolv.conf   xfs      used=  2289.40GB total= 19995.49GB
/etc/hostname      xfs      used=  2289.40GB total= 19995.49GB
/etc/hosts         xfs      used=  2289.40GB total= 19995.49GB
/                  overlay  used=     0.32GB total=   256.00GB
/mnt/volume        tmpfs    used=     0.00GB total=     1.00GB

def is_injected_mount(mount_point):
    """部署契约：容器运行时注入的挂载点不是本节点的业务写路径，不计入本节点用量。"""
    return mount_point in INJECTED_MOUNTS          # ← 函数在、注释对、判决对

def scan_status(write_path):
    used = 0; total = 0
    rows = read_mountinfo()
    for mount_point, fstype, _opts in rows:        # ← 但这里全量遍历
        mp = rec_unescape(mount_point)
        u, t = statvfs_used(mp)
        used += u; total += t                      # ← 把所有盘都加进来

under_pressure = used_ratio >= PRESSURE_RATIO      # 0.80
used_ratio = used / total                          # 分子分母都是「全命名空间累加」

SKIP_PREFIXES = ("/proc", "/sys", "/dev/pts", "/dev/mqueue", "/dev/shm", "/run/lock")

def own_write_mounts(write_path, root_readonly=True):
    out, seen_dev = [], set()
    for row in read_mountinfo_full():                        # 带回 major:minor 与 options
        mp = rec_unescape(row["mount_point"])
        fstype = row["fstype"]
        opts = row["options"].split(",")

        if root_readonly and mp == "/" and fstype == "overlay": continue  # ① 只读根
        if is_injected_mount(mp):                              continue  # ② 注入挂载（终于被调用）
        if is_pseudo_mount(fstype):                            continue  # ③ proc/sysfs/cgroup/fuse.*
        if mp.startswith(SKIP_PREFIXES):                       continue  # ④ 内核注入前缀
        if "ro" in opts:                                       continue  # ⑤ 只读挂载不算业务量
        try:
            u, t = statvfs_used(mp)
        except OSError:
            continue
        if row["major_minor"] in seen_dev:                     continue  # ⑥ 同一块盘 bind 到多处只算一次
        seen_dev.add(row["major_minor"])
        out.append({**row, "mount_point": mp, "used_bytes": u, "total_bytes": t})
    return out

def mount_of(write_path):
    """找 write_path 落在哪个挂载点上（最长匹配）。"""
    target = os.path.realpath(write_path)
    best = None
    for row in read_mountinfo_full():
        mp = rec_unescape(row["mount_point"])
        if target == mp or target.startswith(mp.rstrip("/") + "/"):
            if best is None or len(mp) > len(best["mount_point"]):
                best = {**row, "mount_point": mp}
    ...
    best["used_bytes"], best["total_bytes"] = statvfs_used(best["mount_point"])
    return best

def scan_status(write_path):
    vol = mount_of(write_path)
    used, total = vol["used_bytes"], vol["total_bytes"]
    return {
        "used_bytes": used, "total_bytes": total,
        "used_ratio": round((used / total) if total else 0.0, 6),
        "volume_used_bytes": used,            # ← 显式自证：背压是按谁算的
        "volume_total_bytes": total,
        "volume_mount_point": vol["mount_point"],
        "mount_count": 1,
        "source": f"statvfs(own write mount: {vol['mount_point']})",
        ...
    }

vol_ratio = snap["used_ratio"]              # 现在这个比率就是卷自身的
_state.update({
    ...
    "volume_used_bytes": snap["volume_used_bytes"],
    "volume_total_bytes": snap["volume_total_bytes"],
    "volume_mount_point": snap["volume_mount_point"],
    "under_pressure": vol_ratio >= PRESSURE_RATIO,   # 阈值语义与判据对象终于一致
})

docker compose down -v                     # 基线必须删卷，否则残留 filler 会让断言侥幸
docker compose up -d --build               # COPY 进镜像的文件必须 --build，restart 不生效
docker compose logs client                 # Exited (0) / RESULT: OK
docker compose exec -T node bash -lc '/bin/bash /srv/ops/verify.sh'

used_bytes=912261120 total_bytes=1073741824 used_ratio=0.849609 under_pressure=True
{"ok": false, "written": 0, "errors": ["backpressure: volume under pressure"], "under_pressure": true}
清理后: used=0 ratio=0.0 under=false

cd scenario/2026-09-25-0800
docker compose up -d --build
docker compose logs client                                                    # RESULT: BAD（问题态）
docker compose exec -T node bash -lc '/bin/bash /srv/ops/verify.sh'           # PASS=3 FAIL=5
docker compose down -v