FTS5 keeps deleted entries until their segments are merged, which with
these indexes is close to never. On one machine local_fts held 317 MiB for
40,000 paths, against 20 MiB rebuilt, and search ran four times slower. The
indexes are now compacted once a day after a local scan. A scan that hit the
entry cap or lost a batch no longer prunes the paths it never reached, which
the next scan used to add back (B217).
The "This computer" indexer walks $HOME, and `default_excludes` only kept it
out of the Drive mountpoint and our own state/cache dirs. A home directory
that also holds third-party FUSE mounts (sshfs, rclone) got walked into.
`scan` does ask for `same_file_system(true)`, which looks sufficient and is
not: `ignore` implements it as `is_same_file_system` -> `device_num(path)` ->
`path.metadata()`, run after the directory is queued. Learning that a mount is
foreign requires stat'ing it first, and against a mount whose server is gone
that stat never returns.
The consequence is worse than a stalled scan. The blocked thread sits in
uninterruptible FUSE wait, so it ignores SIGKILL: the daemon can never exit,
systemd's stop times out, and the unreapable process keeps the cache.db lock
the next start needs, turning one dead mount into a permanent restart loop.
No userspace recovery exists once a thread is in that state, so the fix has to
be to never enter it.
Exclude every mountpoint strictly below the scan root, read by path from
/proc/self/mounts (octal-unescaped, so a path with a space still matches).
`filter_entry` runs before the device stat, so the walker never touches them.
Re-read per scan rather than cached at startup: a mount that appeared since
the daemon started is the likeliest to be half-alive.
This does not change what is indexed — a nested mount is a different device,
so it was already going to be skipped. Only the stat in front of that decision
goes away.
Refs: docs/BUGS.md B90
nvrl