System freezes when writing to mergerfs directory about mergerfs HOT 8 OPEN

The trace you've provided shows mergerfs running normally and then when attempting to open the file the OS blocks it.

415   13:45:56.176996 openat(AT_FDCWD, "/mnt/disk1/test.txt", O_RDONLY|O_LARGEFILE|O_CLOEXEC|0x4000000 <unfinished ...>

I'm not able to reproduce this. Can you please make this truly simple as possible. One branch. Try using a tmpfs perhaps.

strace -fvTtt -s 256 -o /tmp/mergerfs.strace.txt mergerfs -f -o cache.files=off,category.create=mfs,minfreespace=0 /mnt/disk1 /offload

# in a different terminal
echo "test" > /offload/test.txt

from mergerfs.

Here is the strace from command
strace -fvTtt -s 256 -o mergerfs.strace.txt mergerfs -f -o cache.files=off,category.create=mfs,minfreespace=0 /mnt/disk2 /offload
mergerfs.strace_single_disk.txt

In another terminal, I ran
echo "this is yet another test" > /offload/text.txt

from mergerfs.

The trace shows the same thing. Open with a weird flag and it blocking. What did you use to install mergerfs? This is Ubuntu 20.04?

from mergerfs.

Yes, its Ubuntu 20.04.
I first installed using apt install, but version 2.28 is available for my distro. Had the same problem with it.
Then I downloaded latest release deb from github and installed with dpkg -i <path-to-deb>

from mergerfs.

I really have no idea. Something is perhaps borked with your setup. I created a VM with 20.04.6, installed mergerfs 2.35.1 for Focal AMD64 and it works as expected. You should try using a tmpfs, building mergerfs from scratch or trying a VM yourself on the same hardware.

from mergerfs.

from mergerfs.

I used 20.04 for years till just this month and had no issue and can't replicate it now with a VM.

If you can reproduce it in a VM that'd be the best for me as then you could share it.

from mergerfs.

I didn't ask you to close this ticket. I just need something reproducible to be able to debug further.

from mergerfs.