fuse-rs
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zargony
Unknown FUSE opcode (39)
ioctl(TCGETS) on a file opened from a filesystem implemented with fuse-rc causes filesystem to be unmounted:
[2019-12-03T13:26:05Z ERROR fuse::request] Unknown FUSE opcode (39)
[2019-12-03T13:26:05Z INFO fuse::session] Unmounted /tmp/m
Such ioctl is issued e.g. by git gui on file .git/HEAD for some reason.
Using Linux kernel version 4.19.85.
I also got this error when doing dd if=<file_in_fuse_mount> skip=<some_offset> of=/dev/null.
After checking the source code, that opcode is behind a feature flag: https://github.com/zargony/fuse-rs/blob/42e29d964e2b24e32e21b179b77e4d0d0a0857ac/fuse-abi/src/lib.rs#L275-L276
Interesting. The kernel driver shouldn't send requests with this opcode at all since we're requesting ABI 7.8 in the FUSE_INIT reply.
I am running Fedora 31 with Linux 5.3.12-300.fc31.x86_64 on the computer with my FUSE server program. According to the upstream Linux kernel source, there is no check against the server's ABI version when sending the IOCTL request [0].
[0] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/fs/fuse/file.c?h=v5.3.12#n2665
Can it just safely ignore (ENOSYS) all unknown opcodes with only a warning instead of error?
i'm also seeing this issue trying to open files with audacity. it's particularly frustrating that the filesystem immediately unmounts and i can't do anything about it, fuse-rs should handle this more gracefully.
This looks like it might be easier to implement on the modernize branch. I got around this issue by defining the rest of the opcodes and basic parsing for them, but returns ENOSYS on opcodes that are not implemented.
Hi all,
Until it's implemented in an actually decent fashion, you might use my quick'n dirty fork that I patched for this problem. Basically, it just replies a simple ENOSYS to any unknown request instead of Err-ing.
