https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=196726
Bug ID: 196726
Summary: fusefs truncates files on read, sometimes returns
wrong data.
Product: Base System
Version: 10.1-RELEASE
Hardware: Any
OS: Any
Status: New
Severity: Affects Some People
Priority: ---
Component: kern
Assignee: freebsd-bugs@FreeBSD.org
Reporter: freebsd-sta...@z42.net
I made a python program to tickle two fusefs problems that may well be the same
problem in different forms, both loosing data. I assume the problem is in the
kernel and not the library, but have not verified this. (I have only looked at
the symptoms.)
#!/usr/bin/env python
#
# FreeBSD (10.1-RELEASE) fuse seems pretty buggy.
# File attributes are cached forever (not tested here), and reported size
# is enforced. (So appending to a file outside the fuse layer has no effect
# if the file is already seen.) And even worse, the first time a file is
# closed (even ro) the reported size is truncated to. This updates the
# mtime, and of course risks discarding data written from somewhere else.
# (This is in test1.)
#
# File contents are also sometimes wrong in surprising ways when a file is
# overwritten. (This is in test2.)
#
# This program takes two directories as arguments, the first one a normal
# mount and the second a fuse mount (e.g. fusexmp or sshfs) of the same dir.
def test2(normal_dir, fuse_dir, test_fn):
from os.path import exists, isdir, join
assert isdir(normal_dir)
assert isdir(fuse_dir)
assert not exists(join(normal_dir, test_fn))
assert not exists(join(fuse_dir, test_fn))
with open(join(normal_dir, test_fn), "wb") as fh:
fh.write("foo")
with open(join(fuse_dir, test_fn), "rb") as fh:
assert fh.read() == "foo", "this should work"
with open(join(normal_dir, test_fn), "wb") as fh:
fh.write("longer")
with open(join(fuse_dir, test_fn), "rb") as fh:
data = fh.read()
assert data == "longer", "fuse misread %s ('longer' != %r)" % (test_fn,
data,)
def test1(normal_dir, fuse_dir, test_fn):
from os.path import exists, isdir, join
assert isdir(normal_dir)
assert isdir(fuse_dir)
assert not exists(join(normal_dir, test_fn))
with open(join(normal_dir, test_fn), "wb") as normal_fh:
normal_fh.write("foo")
normal_fh.flush()
with open(join(fuse_dir, test_fn), "rb") as fuse_fh:
assert fuse_fh.read() == "foo", "this should work"
normal_fh.write("bar")
normal_fh.flush()
with open(join(normal_dir, test_fn), "rb") as normal_fh:
data = normal_fh.read()
assert data == "foobar", "fuse truncated %s ('foobar' != %r)" %
(test_fn, data,)
if __name__ == "__main__":
from sys import argv
from traceback import print_exc
normal_dir, fuse_dir = argv[1:]
try:
test1(normal_dir, fuse_dir, "TEST1")
except Exception:
print "Test 1 failed:"
print_exc()
try:
test2(normal_dir, fuse_dir, "TEST2")
except Exception:
print "Test 2 failed:"
print_exc()
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