new hook: granular ramdisk detection

bin/hooks/reject-ramdisk.py

@@ -0,0 +1,72 @@
+#!/usr/bin/env python3
+
+import os
+import threading
+from argparse import Namespace
+
+from jinja2.nodes import Name
+from copyparty.fsutil import Fstab
+from typing import Any, Optional
+
+
+_ = r"""
+reject an upload if the target folder is on a ramdisk; useful when you
+have a volume where some folders inside are ramdisks but others aren't
+
+example usage as global config:
+    --xbu I,bin/hooks/reject-ramdisk.py
+
+example usage as a volflag (per-volume config):
+    -v srv/inc:inc:r:rw,ed:c,xbu=I,bin/hooks/reject-ramdisk.py
+                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+    (share filesystem-path srv/inc as volume /inc,
+     readable by everyone, read-write for user 'ed',
+     running this plugin on all uploads with the params listed below)
+
+example usage as a volflag in a copyparty config file:
+    [/inc]
+      srv/inc
+      accs:
+        r: *
+        rw: ed
+      flags:
+        xbu: I,bin/hooks/reject-ramdisk.py
+
+parameters explained,
+    I = import; do not fork / subprocess
+
+IMPORTANT NOTE:
+    because this hook is imported inside copyparty, you need to
+    be EXCEPTIONALLY CAREFUL to avoid side-effects, for example
+    DO NOT os.chdir() or anything like that, and also make sure
+    that the name of this file is unique (cannot be the same as
+    an existing python module/library)
+"""
+
+
+mutex = threading.Lock()
+fstab: Optional[Fstab] = None
+
+
+def main(ka: dict[str, Any]) -> dict[str, Any]:
+    global fstab
+    with mutex:
+        log = ka["log"]  # this is a copyparty NamedLogger function
+        if not fstab:
+            log("<HOOK:RAMDISK> creating fstab", 6)
+            args = Namespace()
+            args.mtab_age = 1  # cache the filesystem info for 1 sec
+            fstab = Fstab(log, args, False)
+
+        ap = ka["ap"]  # abspath the upload is going to
+        fs, mp = fstab.get(ap)  # figure out what the filesystem is
+        ramdisk = fs in ("tmspfs", "overlay")  # looks like a ramdisk?
+
+        # log("<HOOK:RAMDISK> fs=%r" % (fs,))
+
+        if ramdisk:
+            t = "Upload REJECTED because destination is a ramdisk"
+            return {"rc": 1, "rejectmsg": t}
+
+        return {"rc": 0}