Move the inline filesystem skip logic from pollVMsAndContainersEfficient
into a reusable ShouldSkipFilesystem function. This consolidates filtering
for virtual filesystems (tmpfs, cgroup, etc.), network mounts (nfs, cifs,
fuse), and special mountpoints (/dev, /proc, /snap, etc.) into one tested
location.
Reduces cyclomatic complexity of pollVMsAndContainersEfficient and adds
28 test cases covering virtual fs types, network mounts, special mounts,
Windows paths, and edge cases.
Squashfs snap mounts on Ubuntu (and similar read-only filesystems like
erofs on Home Assistant OS) always report near-full usage and trigger
false disk alerts. The filter logic existed in Proxmox monitoring but
wasn't applied to host agents.
Changes:
- Extract read-only filesystem filter to shared pkg/fsfilters package
- Apply filter in hostmetrics.collectDisks() for host/docker agents
- Apply filter in monitor.ApplyHostReport() for backward compatibility
- Convert internal/monitoring/fs_filters.go to wrapper functions
This prevents squashfs, erofs, iso9660, cdfs, udf, cramfs, romfs, and
saturated overlay filesystems from generating alerts. Filtering happens
at both collection time (agents) and ingestion time (server) to ensure
older agents don't cause false alerts until they're updated.
