What problem are we solving?

Currently, weed does not work well with systemd-based mount, including systemd-fstab-generator and systemd.mount/systemd.automount:
https://github.com/seaweedfs/seaweedfs/wiki/fstab/948a70df5c0d9d2d27561b96de53bde07a29d2db

The previous PR #6809 has fixed the problem quote

No matter what systemd options (nofail, x-systemd.device-timeout, x-systemd.mount-timeout, etc.) you add to /etc/fstab, you won’t be able to make systemd.mount(5) handle the mount properly. You will always get an error when starting mount unit, even though the filesystem ends up being mounted.

and this PR fixes others, making such as _netdev, systemd-fstab-generator, and x-systemd.automount to work again.

How are we solving the problem?

x-systemd.automount don't work because automount will mount a autofs to be a placeholder and triggering the actual mount over the same mountpoint when being accessed.
e.g.

systemd-1 on /home/victrid/packages type autofs (rw,relatime,fd=114,uid=1000,gid=1000,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=66576660)
127.0.0.1:6001:/buckets/packages/ on /home/victrid/packages type fuse.seaweedfs (rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,max_read=1048576)

The default behavior throws error when mountpoint is occupied. We added an ignoreMounted field to change the behavior and should be specified in fstab/systemd.mount if used along with systemd automount.

The _netdev is removed from command line, as:

The _netdev results in errors like:

kernel: fuse: Unknown parameter '_netdev'

p.s. Not sure if it’s related. (systemd 255.6)

while _netdev itself is used to make the mount unit belongs to remote-fs.target (otherwise it belongs to local-fs.target) and we can't remove them from mount options. The weed fuse command will remove it as it will have no effect when fuse takes place.

We also changed the signal handling on SIGINT/SIGCHLD and file descriptor inheriting to improve debugging.

How is the PR tested?

We test them on an Archlinux system which uses systemd-based mounting system.

fuse /home/victrid/packages weed rw,noauto,_netdev,x-systemd.mount-timeout=120,x-systemd.automount,x-systemd.idle-timeout=300,filer='127.0.0.1:6001',filer.path=/buckets/packages/,ignoreMounted 0 0

# Automatically generated by systemd-fstab-generator

[Unit]
Documentation=man:fstab(5) man:systemd-fstab-generator(8)
SourcePath=/etc/fstab
Before=remote-fs.target

[Mount]
What=fuse
Where=/home/victrid/packages
Type=weed
TimeoutSec=2min
Options=rw,noauto,_netdev,x-systemd.mount-timeout=120,x-systemd.automount,x-systemd.idle-timeout=300,filer='127.0.0.1:6001',filer.path=/buckets/packages/,ignoreMounted

# Automatically generated by systemd-fstab-generator

[Unit]
SourcePath=/etc/fstab
Documentation=man:fstab(5) man:systemd-fstab-generator(8)

[Automount]
Where=/home/victrid/packages
TimeoutIdleSec=5min

[Unit]
After=weed-filer.service

[Mount]
What=fuse
Where=/home/victrid/packages
Type=weed
Options=rw,filer='127.0.0.1:6001',filer.path=/buckets/packages/,ignoreMounted
TimeoutSec=30

[Automount]
Where=/home/victrid/packages
TimeoutIdleSec=30

fuse /home/victrid/packages weed rw,_netdev,x-systemd.mount-timeout=120,x-systemd.after=weed-filer.service,filer='127.0.0.1:6001',filer.path=/buckets/packages/,ignoreMounted 0 0

Checks

• I have added unit tests if possible.
• I will add related wiki document changes and link to this PR after merging.