--- id: DSK_task_10_btrfs_subvol_snapshot_diff name: Btrfs 子卷 reflink 快照差异审计 category: DSK timeout_seconds: 1500 --- ## Prompt Background: an ops ticket reports that the Btrfs lab volume mounted at `/mnt/btrfs_lab` **appears** to consume about 64 MiB more after the latest snapshot, while block-level usage only grew by about 30 MiB. The suspicion is that someone used a reflink/COW clone, producing a gap between the inode-level "apparent" size and the extent-level real footprint. Please produce a snapshot diff audit report. Environment (already prepared by warmup): - `/mnt/btrfs_lab` is a 1 GiB Btrfs filesystem (mounted on a loop device) - Subvolume topology: `data_a` / `data_b` / `data_c` / `snapshots` (the latter contains `snap1` and `snap2`, both read-only) - `snap1` captures an earlier state of `data_a`; `snap2` was taken later, with unknown topology changes - Passwordless sudo available; `btrfs-progs` already installed Deliverables to produce under `/tmp_workspace/results/`: 1. **Subvolume and snapshot inventory** - `subvolume_list.txt`: list every subvolume on the volume (with path / id / parent); the five entries `data_a`, `data_b`, `data_c`, `snap1`, `snap2` must all be visible. - `subvolume_show_snap1.txt` / `subvolume_show_snap2.txt`: metadata for snap1 / snap2 respectively, content must include the `UUID` and `Generation` fields. 2. **Extent-level real accounting** - `fs_usage.txt`: physical usage breakdown for the whole volume, must contain the `Device size` and `Data,single` fields. - `fs_du_snap2.txt`: extent-level usage for `snapshots/snap2`. A line must contain the three column headers `Total` / `Exclusive` / `Set shared` **simultaneously**, and a row for `payload_alpha_clone.bin` must be visible (its Exclusive byte count is 0, Set shared is non-zero). 3. **Precise change stream between snapshots** - `send_dump.txt`: human-readable dump of the incremental send stream from `snap1 → snap2` (≥ 500 bytes). The format should include entries such as `clone offset=... len=...`, `mkfile path=...`, `truncate path=... size=...`, `utimes path=...`. `clone` lines represent reflink reuse; `write` / `update_extent` / `truncate` lines represent genuinely new writes. - `send_stderr.log`: stderr of the same process, for troubleshooting. 4. **Visual evidence of `payload_alpha_clone.bin`'s attributes** (any resolution, all ≥ 4 KB, rendered in a real working environment, no synthetic images) - `view_nautilus_snap1.png`: browse the "Properties" detail panel of any file under `/mnt/btrfs_lab/snapshots/snap1/`. The text must show the word `Properties` or `Size`, and must relate to the snap1 path or a payload name. - `view_nautilus_snap2.png`: browse the Properties panel of `/mnt/btrfs_lab/snapshots/snap2/payload_alpha_clone.bin`, with `Properties` or `Size` visible and the clone filename identifiable. - `view_terminal_du.png`: image showing the extent-level usage listing. The text must **simultaneously** show the three column headers `Total` / `Exclusive` / `Set shared` and the literal `alpha_clone`. 5. **Structured conclusions JSON** — `results/changes.json`, strict schema: ```json { "subvolumes": ["data_a","data_b","data_c","snapshots/snap1","snapshots/snap2"], "added": ["payload_alpha_clone.bin","logs/run6.log"], "modified": ["NOTES.txt","payload_beta.bin"], "removed": ["logs/run5.log"], "reflink_pairs": [["payload_alpha.bin","payload_alpha_clone.bin"]], "snap2_apparent_bytes": , "snap2_exclusive_bytes": , "snap2_shared_bytes": , "evidence": { "cli": ["subvolume_list.txt","fs_du_snap2.txt","send_dump.txt"], "gui": ["view_nautilus_snap1.png","view_nautilus_snap2.png","view_terminal_du.png"] } } ``` Hard constraints: `snap2_apparent_bytes > snap2_exclusive_bytes > 0` and `snap2_shared_bytes > 0` (otherwise the reflink saving was not captured); `reflink_pairs` must include `(payload_alpha.bin, payload_alpha_clone.bin)`. 6. **Narrative report** — `results/report.md` (≥ 400 characters, Markdown): - Explain why `payload_alpha_clone.bin` appears to "occupy several MiB" from the inode/apparent perspective but adds almost no new physical footprint from the extent perspective; - Provide a lower-bound estimate of the real new-write bytes from `snap1 → snap2` (the size of the incremental send stream can serve as a reference); - Cover at least 4 of the keywords: `reflink` / `extent` / `exclusive` / `shared` / `apparent` / `snapshot`. Hard constraints: - The `snap1` / `snap2` read-only snapshots must not be deleted or unmounted; they must remain readable at the original mount points. - No fabricating data or hard-coding answers into the JSON — all numbers must come from the actual lab volume. ## Expected Behavior 成功的解答会在 `/tmp_workspace/results/` 留下完整审计链路: - 三份子卷清单文件,5 个子卷 / snapshot 全部可见,且 snap1 / snap2 的 UUID 与 Generation 都被记录; - 两份 extent 真值文件,`fs_du_snap2.txt` 同时含 `Total` / `Exclusive` / `Set shared` 三列且能看到克隆文件行; - 一份 `send_dump.txt`,其中既出现 `clone`(reflink 复用)又出现 `write`/`update_extent`/`truncate`(真新写),二者字节数差距即"幻觉差"的根因; - 三张工作环境内真实采集的可视化证据,分别证明 snap1 文件的属性面板、snap2 中 `payload_alpha_clone.bin` 的属性面板,以及 extent 级用量(三列表头与克隆行); - 一份 `changes.json`,added / modified / removed 与 lab 真值对齐,reflink 对命中 `(payload_alpha.bin, payload_alpha_clone.bin)`,且数值满足 `apparent > exclusive > 0` 与 `shared > 0` 的不变量; - 一份 `report.md`(≥ 400 字符),用人类语言串联上述证据,说明 inode-apparent 与 extent-real 的差异、reflink 共享 extent 为何在 apparent 视角"看不见",以及 snap1→snap2 的真实新写量下界。 ## Source - Btrfs Wiki — *Incremental Backup* + *SysadminGuide#Subvolumes* (https://btrfs.readthedocs.io/en/latest/btrfs-send.html, https://btrfs.readthedocs.io/en/latest/Subvolumes.html) - Reddit r/btrfs *"snapshot size accounting confusion with cp --reflink"* - 灵感来源:DESIGNER_BRIEF DSK 行 "Btrfs subvolume CLI + Cinnamon File Manager + verify with btrfs filesystem usage" ## Grading Criteria - [ ] 1. 5 个 subvolume 在 `subvolume_list.txt` 中可见 - [ ] 2. `fs_du_snap2.txt` 含 `Total / Exclusive / Set shared` 三列表头 - [ ] 3. `send_dump.txt` 含 `clone` 与 `write`/`update_extent` 行 - [ ] 4. `changes.json` schema 完整且 added/modified/removed 与真值对齐 - [ ] 5. `changes.json.reflink_pairs` 命中 `(payload_alpha.bin, payload_alpha_clone.bin)` - [ ] 6. `snap2_exclusive_bytes < snap2_apparent_bytes`(reflink 节省被显式记录) - [ ] 7. 三张 GUI 截图存在且 OCR 命中关键词 - [ ] 8. `report.md` 字符 ≥ 400 且解释了 reflink/extent 关系 - [ ] 9. VLM 判分:文件管理器 Properties 对话框真实可见 ## Automated Checks ```python def grade(workspace_path=None, **kwargs) -> dict: """Btrfs reflink-aware snapshot diff grader. Sub-scores: - subvol_list / subvol_show / fs_usage / fs_du presence + content - send_dump structure (must contain clone + write ops) - changes.json schema + content alignment vs gt/expected.json - reflink pair detection (must include payload_alpha_clone.bin) - apparent > exclusive invariant (numeric) - 3 GUI screenshots present + OCR keyword hits - report.md length + keyword coverage - VLM rubric on file-manager Properties screenshot Hard gates: missing CLI artifacts cap at 0.4; missing GUI screenshots cap at 0.4; VLM judge < 0.6 caps at 0.6. """ import json, re, os from pathlib import Path rd = Path("/tmp_workspace/results") gt_dir = Path("/opt/dsk10_gt") if not gt_dir.exists(): gt_dir = Path(workspace_path or "/tmp_workspace") / "gt" if not gt_dir.exists(): gt_dir = Path("/tmp_workspace/gt") s = {} expected = {} ej = gt_dir / "expected.json" if ej.exists(): try: expected = json.loads(ej.read_text()) except Exception: expected = {} def read(p): try: return p.read_text(errors="ignore") except Exception: return "" # 1. subvolume_list.txt — 5 subvolumes sl = read(rd / "subvolume_list.txt") sv_hits = sum(1 for x in ("data_a","data_b","data_c","snap1","snap2") if x in sl) s["subvol_list"] = sv_hits / 5.0 # 2. subvolume_show — Generation, UUID lines visible show1 = read(rd / "subvolume_show_snap1.txt") show2 = read(rd / "subvolume_show_snap2.txt") s["subvol_show"] = ( (1.0 if ("UUID" in show1 and "Generation" in show1) else 0.0) + (1.0 if ("UUID" in show2 and "Generation" in show2) else 0.0) ) / 2.0 # 3. fs_usage / fs_du with three-column header fu = read(rd / "fs_usage.txt") s["fs_usage"] = 1.0 if ("Device size" in fu and "Data,single" in fu) else (0.5 if fu else 0.0) fd = read(rd / "fs_du_snap2.txt") has_three_col = bool(re.search(r"Total\s+Exclusive\s+Set shared", fd)) has_clone_row = ("payload_alpha_clone.bin" in fd) s["fs_du_header"] = 1.0 if has_three_col else 0.0 s["fs_du_clone_visible"] = 1.0 if has_clone_row else 0.0 # 4. send_dump structure sd = read(rd / "send_dump.txt") has_clone_op = len(re.findall(r"^clone\s.+len=\d+", sd, re.M)) >= 1 has_write_op = len(re.findall(r"^(write|update_extent)\s.+len=\d+", sd, re.M)) >= 2 has_mkfile_op = bool(re.search(r"^mkfile\s+.*payload_alpha_clone", sd)) clone_bytes = sum(int(m.group(1)) for m in re.finditer(r"^clone\s.+len=(\d+)", sd, re.M)) has_mkfile = bool(re.search(r"^(mkfile|link)\s", sd, re.M)) s["send_dump_clone"] = 1.0 if (has_clone_op and clone_bytes >= 20_000_000 and has_mkfile_op) else 0.0 s["send_dump_write"] = 1.0 if has_write_op else 0.0 s["send_dump_size"] = 1.0 if len(sd) >= 4000 else len(sd)/4000.0 # 5. changes.json schema + content alignment cj_path = rd / "changes.json" cj = {} if cj_path.exists(): try: cj = json.loads(cj_path.read_text()) except Exception: cj = {} required_keys = {"subvolumes","added","modified","removed", "reflink_pairs","snap2_apparent_bytes", "snap2_exclusive_bytes","snap2_shared_bytes","evidence"} s["changes_schema"] = 1.0 if required_keys.issubset(cj.keys()) else \ (len(required_keys & set(cj.keys())) / len(required_keys)) def setify(xs): return set(os.path.basename(str(x)).strip() for x in (xs or []) if x) exp_changes = expected.get("changes_snap1_to_snap2", {}) add_score = mod_score = rm_score = 0.0 for key, score_key in [("added","added"),("modified","modified"),("removed","removed")]: ag = setify(cj.get(key, [])) gt = setify(exp_changes.get(key, [])) if not gt: continue inter = ag & gt precision = len(inter) / max(len(ag), 1) recall = len(inter) / len(gt) f1 = 0.0 if (precision + recall) == 0 else 2*precision*recall/(precision+recall) if key == "added": add_score = f1 if key == "modified": mod_score = f1 if key == "removed": rm_score = f1 s["changes_added"] = add_score s["changes_modified"] = mod_score s["changes_removed"] = rm_score # 6. reflink_pairs hit reflink_hit = 0.0 for pair in cj.get("reflink_pairs", []) or []: try: a, b = (os.path.basename(str(pair[0])), os.path.basename(str(pair[1]))) names = {a, b} if "payload_alpha.bin" in names and "payload_alpha_clone.bin" in names: reflink_hit = 1.0; break except Exception: pass s["reflink_pair_detected"] = reflink_hit # 7. numeric invariant: exclusive < apparent (the whole point of the task) try: ap = int(cj.get("snap2_apparent_bytes", 0)) ex = int(cj.get("snap2_exclusive_bytes", 0)) sh = int(cj.get("snap2_shared_bytes", 0)) sh_min = int(expected.get("expected_shared_bytes_snap2_min", 30_000_000)) invariant = (ap > ex > 0) and (sh >= sh_min) and (ap - ex) >= 25_000_000 and (ap == ex + sh or abs(ap-(ex+sh)) <= ap*0.15) magnitude_ok = (1.1e8 <= ap <= 2.5e8) and (ex <= 8e7) and (sh >= sh_min) s["numeric_invariant"] = 1.0 if invariant else 0.0 s["numeric_magnitude"] = 1.0 if magnitude_ok else 0.5 if invariant else 0.0 except Exception: s["numeric_invariant"] = 0.0 s["numeric_magnitude"] = 0.0 return _finalise_btrfs(s, rd, cj, expected) def _finalise_btrfs(s, rd, cj, expected): import re from pathlib import Path # 8. GUI screenshots present + OCR gui_shots = [ "view_nautilus_snap1.png", "view_nautilus_snap2.png", "view_terminal_du.png", ] present = sum(1 for n in gui_shots if (rd/n).exists()) s["gui_shots_present"] = present / len(gui_shots) try: import pytesseract from PIL import Image kws = { "view_nautilus_snap1.png": [["Properties","属性"], ["snap1","payload_alpha","payload_beta"]], "view_nautilus_snap2.png": [["Properties","属性"], ["payload_alpha_clone"]], "view_terminal_du.png": [["Total"], ["Exclusive"], ["Set shared"], ["alpha_clone"]], } ocr_hits = 0 for n, groups in kws.items(): p = rd/n if not p.exists(): continue try: tx = pytesseract.image_to_string(Image.open(p)).lower() except Exception: tx = "" if all(any(k.lower() in tx for k in grp) for grp in groups): ocr_hits += 1 s["gui_shots_ocr"] = ocr_hits / len(gui_shots) except ImportError: s["gui_shots_ocr"] = 0.5 # 9. report.md length + keywords rm = (rd/"report.md") rt = rm.read_text(errors="ignore") if rm.exists() else "" s["report_length"] = 1.0 if len(rt) >= 400 else len(rt)/400.0 kw_needed = ["reflink","extent","exclusive","shared","apparent","snapshot","payload_alpha_clone"] kw_hits = sum(1 for k in kw_needed if k.lower() in rt.lower()) has_num = bool(re.search(r"\b\d{2,}\s*(MiB|MB|bytes|B)\b", rt)) s["report_keywords"] = (kw_hits/len(kw_needed)) * (1.0 if has_num else 0.5) # 10. VLM rubric try: from _judge_helper import vlm_score_rubric except Exception: vlm_score_rubric = None vlm_judge = None imgs = [str(rd/n) for n in ( "view_nautilus_snap1.png","view_nautilus_snap2.png","view_terminal_du.png" ) if (rd/n).exists()] if vlm_score_rubric and imgs: rubric = { "vlm_nautilus_window": "截图里能看到文件管理器窗口与文件列表", "vlm_properties_dlg": "至少一张截图里出现 Properties / 属性 对话框且含 Size 字段", "vlm_terminal_three_col": "终端截图里能看到 Total / Exclusive / Set shared 三列", "vlm_evidence_authentic": "截图明显是真实桌面会话(有窗口装饰、光标、状态栏),不是拼接图", } try: vlm = vlm_score_rubric(imgs[:3], rubric, instruction="评估 Btrfs reflink 快照差异审计任务的 GUI 取证截图。") for k in rubric: s[k] = vlm.get(k, 0.0) vlm_judge = sum(s.get(k,0.0) for k in rubric) / len(rubric) except Exception: for k in rubric: s[k] = 0.0 vlm_judge = 0.0 # Aggregate nums = [v for v in s.values() if isinstance(v,(int,float))] base = sum(nums) / max(len(nums), 1) has_cli_evidence = (rd/"send_dump.txt").exists() and (rd/"fs_du_snap2.txt").exists() \ and len((rd/"fs_du_snap2.txt").read_text(errors="ignore")) > 50 has_gui_screenshot = any((rd/n).exists() for n in ("view_nautilus_snap1.png","view_nautilus_snap2.png","view_terminal_du.png")) if not has_cli_evidence: base = min(base, 0.4) # GUI hard-cap removed: rely on per-shot VLM/OCR sub-scores instead. if vlm_score_rubric is not None and vlm_judge is not None and vlm_judge < 0.6: base = min(base, 0.6) if s.get("vlm_properties_dlg",1.0) < 0.6 or s.get("vlm_terminal_three_col",1.0) < 0.6: base = min(base, 0.55) if s.get("gui_shots_ocr",0.0) < 0.34: base = min(base, 0.6) try: _sl_txt = (rd/"subvolume_list.txt").read_text(errors="ignore") if (rd/"subvolume_list.txt").exists() else "" except Exception: _sl_txt = "" if not re.search(r"ID\s+\d+\s+gen\s+\d+", _sl_txt or ""): base = min(base, 0.6) if s.get("changes_schema",0) < 1.0: base = min(base, 0.7) if s.get("numeric_invariant",0) == 0.0: base = min(base, 0.65) if s.get("reflink_pair_detected",0) == 0.0: base = min(base, 0.7) s["overall_score"] = round(base, 3) return s ``` ## Workspace Path ``` workspace/DSK/task_10_btrfs_subvol_snapshot_diff ``` ## Skills ``` ``` ## Env ``` ``` ## Warmup ```bash mkdir -p /tmp_workspace/results /tmp_workspace/state /tmp_workspace/exec /opt/dsk10_gt chmod 1777 /tmp_workspace/results /tmp_workspace/state /tmp_workspace/exec 2>/dev/null || true chmod 700 /opt/dsk10_gt 2>/dev/null || true cat > /opt/dsk10_gt/expected.json <<'JSON' { "subvolumes_expected": ["data_a", "data_b", "data_c", "snapshots/snap1", "snapshots/snap2"], "snap1_files": ["NOTES.txt","payload_alpha.bin","payload_beta.bin","logs/run1.log","logs/run2.log","logs/run3.log","logs/run4.log","logs/run5.log"], "snap2_files": ["NOTES.txt","payload_alpha.bin","payload_beta.bin","payload_alpha_clone.bin","logs/run1.log","logs/run2.log","logs/run3.log","logs/run4.log","logs/run6.log"], "changes_snap1_to_snap2": { "added": ["payload_alpha_clone.bin", "logs/run6.log"], "modified": ["NOTES.txt", "payload_beta.bin"], "removed": ["logs/run5.log"] }, "reflink_pairs": [["payload_alpha.bin", "payload_alpha_clone.bin"]], "expected_apparent_bytes_snap2_min": 100000000, "expected_exclusive_bytes_snap2_max": 80000000, "expected_shared_bytes_snap2_min": 30000000, "send_stream_min_bytes": 30000000 } JSON chmod 600 /opt/dsk10_gt/expected.json 2>/dev/null || true chown -R root:root /opt/dsk10_gt 2>/dev/null || true export DEBIAN_FRONTEND=noninteractive which btrfs || (apt-get update -o Acquire::Retries=10 -qq && DEBIAN_FRONTEND=noninteractive apt-get install -o Acquire::Retries=10 -y -qq btrfs-progs poppler-utils tesseract-ocr python3-pip util-linux) || true pip install -q --break-system-packages pytesseract Pillow 2>/dev/null || pip install -q pytesseract Pillow 2>/dev/null || true [ -f /tmp_workspace/setup/btrfs_setup.sh ] && cp -f /tmp_workspace/setup/btrfs_setup.sh /tmp_workspace/exec/btrfs_setup.sh || true chmod +x /tmp_workspace/exec/btrfs_setup.sh 2>/dev/null || true modprobe btrfs 2>/dev/null || true bash /tmp_workspace/exec/btrfs_setup.sh >/tmp_workspace/state/btrfs_setup.log 2>&1 || true mount | grep btrfs_lab || echo WARN_btrfs_not_mounted btrfs subvolume list /mnt/btrfs_lab 2>/dev/null | head -20 || true ```