Spaces:
Paused
Paused
File size: 10,503 Bytes
bc35a94 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 | import shutil
import subprocess
import tempfile
import time
import uuid
from pathlib import Path
DEFAULT_VOLATILE_ROOT = "/dev/shm"
class OverlayFSManager:
"""manages overlayfs stacks for sub second filesystem state resets"""
def __init__(
self,
base_dir: str | None = None,
*,
volatile_root: str | None = None,
):
"""
base dir is the parent directory where the merged mount point is created
volatile root is the ram backed filesystem where upperdir and workdir live
defaults to /dev/shm so resets never hit persistent disk io
"""
if base_dir is not None:
self._base_dir = Path(base_dir)
self._base_dir.mkdir(parents=True, exist_ok=True)
self._owns_base_dir = False
else:
self._base_dir = Path(tempfile.mkdtemp(prefix="overlayfs_"))
self._owns_base_dir = True
volatile_candidate = Path(volatile_root) if volatile_root is not None else Path(DEFAULT_VOLATILE_ROOT)
self._volatile_base = self._select_volatile_base(volatile_candidate)
self._volatile_dir = self._volatile_base / f"overlay_{uuid.uuid4().hex}"
self._volatile_dir.mkdir(parents=True, exist_ok=True)
print(f"overlay volatile root {self._volatile_dir}")
self._lowerdir: Path | None = None
self._upperdir: Path | None = None
self._workdir: Path | None = None
self._merged: Path | None = None
self._mounted = False
self._mount_type: str | None = None
@property
def lowerdir(self) -> Path | None:
return self._lowerdir
@property
def upperdir(self) -> Path | None:
return self._upperdir
@property
def workdir(self) -> Path | None:
return self._workdir
@property
def merged(self) -> Path | None:
return self._merged
@property
def is_mounted(self) -> bool:
return self._mounted
@property
def mount_type(self) -> str | None:
return self._mount_type
@property
def volatile_dir(self) -> Path:
return self._volatile_dir
def create_stack(self, lowerdir: str | Path) -> Path:
"""
creates the overlay directory stack given a lowerdir path
upperdir and workdir are pinned to the volatile ram disk
returns the path to the merged directory
"""
lowerdir = Path(lowerdir).resolve()
if not lowerdir.is_dir():
raise FileNotFoundError(f"lowerdir does not exist {lowerdir}")
self._lowerdir = lowerdir
self._upperdir = self._volatile_dir / "upper"
self._workdir = self._volatile_dir / "work"
self._merged = self._base_dir / "merged"
self._upperdir.mkdir(exist_ok=True)
self._workdir.mkdir(exist_ok=True)
self._merged.mkdir(exist_ok=True)
print(f"overlay stack created upper {self._upperdir} work {self._workdir} merged {self._merged}")
return self._merged
def mount(self) -> None:
"""
mounts the overlay filesystem trying kernel overlayfs first
then falling back to fuse overlayfs for unprivileged contexts
"""
if self._mounted:
raise RuntimeError("overlay already mounted")
if self._merged is None:
raise RuntimeError("create stack must be called before mount")
try:
print("overlay kernel mount start")
self._mount_kernel()
self._mount_type = "kernel"
print("overlay mounted via kernel overlayfs")
except (PermissionError, OSError, subprocess.CalledProcessError) as exc:
print(f"overlay kernel mount failed {type(exc).__name__.lower()}")
try:
print("overlay fuse mount start")
self._mount_fuse()
self._mount_type = "fuse"
print("overlay mounted via fuse overlayfs")
except (FileNotFoundError, OSError, subprocess.CalledProcessError) as fuse_exc:
print(f"overlay fuse mount failed {type(fuse_exc).__name__.lower()}")
self._mount_copy()
self._mount_type = "copy"
print("overlay mounted via copy fallback")
self._mounted = True
def _mount_copy(self) -> None:
if self._lowerdir is None or self._merged is None:
raise RuntimeError("copy fallback requires lowerdir and merged path")
self._clear_directory(self._merged)
shutil.copytree(self._lowerdir, self._merged, dirs_exist_ok=True, symlinks=True)
def _mount_kernel(self) -> None:
mount_opts = (
f"lowerdir={self._lowerdir},"
f"upperdir={self._upperdir},"
f"workdir={self._workdir}"
)
result = subprocess.run(
["mount", "-t", "overlay", "overlay", "-o", mount_opts, str(self._merged)],
capture_output=True,
text=True,
timeout=10,
)
if result.returncode != 0:
raise PermissionError(f"kernel mount failed {result.stderr.strip()}")
def _mount_fuse(self) -> None:
fuse_bin = shutil.which("fuse-overlayfs")
if fuse_bin is None:
raise FileNotFoundError("fuse-overlayfs binary not found in path")
print(f"overlay fuse binary {fuse_bin}")
mount_opts = (
f"lowerdir={self._lowerdir},"
f"upperdir={self._upperdir},"
f"workdir={self._workdir}"
)
result = subprocess.run(
[fuse_bin, "-o", mount_opts, str(self._merged)],
capture_output=True,
text=True,
timeout=10,
)
if result.returncode != 0:
raise OSError(f"fuse overlayfs mount failed {result.stderr.strip()}")
def reset(self) -> float:
"""
resets the overlay by clearing upperdir contents and recreating workdir
upperdir/workdir live on tmpfs so this stays sub 10ms on warm kernels
returns the reset latency in milliseconds
"""
if not self._mounted:
raise RuntimeError("overlay is not mounted")
start = time.perf_counter()
mount_type = self._mount_type
if mount_type == "copy":
if self._merged is None:
raise RuntimeError("copy fallback merged path missing")
self._mount_copy()
self._mount_type = "copy"
else:
self.unmount()
self._purge_volatile_pair()
if self._merged is not None:
self._merged.mkdir(exist_ok=True)
if mount_type == "kernel":
self._mount_kernel()
self._mount_type = "kernel"
else:
self._mount_fuse()
self._mount_type = "fuse"
self._mounted = True
elapsed_ms = (time.perf_counter() - start) * 1000.0
print(f"overlay reset {elapsed_ms:.1f}ms")
return elapsed_ms
def unmount(self) -> None:
"""unmounts the overlay filesystem"""
if not self._mounted:
return
if self._mount_type == "copy":
self._mounted = False
self._mount_type = None
print("overlay unmounted")
return
if self._mount_type == "fuse":
result = subprocess.run(
["fusermount", "-u", str(self._merged)],
capture_output=True,
text=True,
timeout=10,
)
if result.returncode != 0:
subprocess.run(
["fusermount3", "-u", str(self._merged)],
capture_output=True,
text=True,
timeout=10,
)
else:
subprocess.run(
["umount", str(self._merged)],
capture_output=True,
text=True,
timeout=10,
)
self._mounted = False
self._mount_type = None
print("overlay unmounted")
def _purge_volatile_pair(self) -> None:
"""wipes upperdir and workdir trees from the volatile ram disk"""
for target in (self._upperdir, self._workdir):
if target is None:
continue
if target.exists():
shutil.rmtree(target, ignore_errors=True)
target.mkdir(parents=True, exist_ok=True)
def _clear_directory(self, directory: Path) -> None:
directory.mkdir(parents=True, exist_ok=True)
for entry in directory.iterdir():
if entry.is_dir() and not entry.is_symlink():
shutil.rmtree(entry)
else:
entry.unlink()
def _select_volatile_base(self, preferred: Path) -> Path:
"""picks a ram backed root or falls back to the system temp dir"""
candidates: list[Path] = [preferred]
if preferred != Path(DEFAULT_VOLATILE_ROOT):
candidates.append(Path(DEFAULT_VOLATILE_ROOT))
candidates.append(Path(tempfile.gettempdir()))
for candidate in candidates:
try:
candidate.mkdir(parents=True, exist_ok=True)
probe = candidate / f".probe_{uuid.uuid4().hex}"
probe.touch()
probe.unlink()
return candidate
except OSError as exc:
print(f"overlay volatile candidate rejected {candidate} {type(exc).__name__.lower()}")
continue
raise RuntimeError("no writable volatile root available")
def cleanup(self) -> None:
"""unmounts if mounted and recursively deletes all overlay directories"""
self.unmount()
for d in [self._upperdir, self._workdir, self._merged]:
if d is not None and d.exists():
shutil.rmtree(d, ignore_errors=True)
if self._volatile_dir.exists():
shutil.rmtree(self._volatile_dir, ignore_errors=True)
if self._owns_base_dir and self._base_dir.exists():
shutil.rmtree(self._base_dir, ignore_errors=True)
self._lowerdir = None
self._upperdir = None
self._workdir = None
self._merged = None
self._mount_type = None
print("overlay cleanup complete")
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, exc_tb):
self.cleanup()
return False
|