50077a0c318663c830d9758d5517bd6a51e7574c
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Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 Gabriel Brown
|
86825e7327 |
Judge the document portal by its mount, not by its service
No flatpak would launch. Every one of them failed in bwrap with "Can't find
source path /run/user/1000/doc/by-app/<id>", because xdg-document-portal's fuse
mount was gone -- /run/user/1000/doc was a plain empty directory. That mount is
bound into every sandbox bwrap builds, so losing it takes out all 34 flatpaks at
once, never a subset.
It had been gone for three days. The shipped unit is Type=dbus with Restart=no,
so nothing retries it on failure: after it exited 21 it came back only because a
flatpak called its bus name two seconds later, and that activation landed on the
dying instance's mountpoint and came up with no mount at all. systemctl reports
active (running) either way -- the fusermount3 helper is still sitting there as a
child, in this case for two and a half days without ever completing the mount.
Nothing running notices, which is what makes it so quiet. A sandbox needs the
mount only while it is being constructed, so everything already open keeps
working and the symptom arrives whenever you next open a flatpak you had not
opened yet. Here that was three days later, and it presented as "gearlever is
missing" -- an application that was installed, healthy, and entirely innocent.
Two changes, because there are two failures: it does not recover, and nothing
says so.
The drop-in clears the mountpoint before each start, so an activation that
follows a crash lands on clean ground. ExecStartPre rather than ExecStopPost
precisely because nothing restarts this unit -- the next start is whenever
something next wants it, and that is the moment that has to be safe. `-` because
a clean start has nothing to unmount and fusermount3 exits 1 saying so.
/etc/systemd/user rather than a per-user drop-in so it covers every account, and
change-settings reloads the user manager so it applies without a re-login.
The check asks the mount table whether $XDG_RUNTIME_DIR/doc is mounted
fuse.portal. Deliberately not a service probe, and deliberately not folded into
desktop.portals: that one asks about xdg-desktop-portal, a different service
which was up and healthy throughout. Service state is exactly the question that
lied here, so asking it again in a new place would have been no check at all.
Warning carries a restart repair, verified end to end rather than assumed.
The mount table is injectable, like every other path this script reads, so the
contract covers unmounted, wrong-filesystem-at-the-right-path, and unreadable
against written fixtures rather than against whatever /proc happens to say --
coupling the test to this machine's live flatpak state is the same mistake in
miniature. Stubbing the check to always return ok fails the contract, which was
confirmed rather than hoped.
What is not fixed is the crash itself: one occurrence, and restarting the
service to get the desktop working destroyed the evidence. The exit was 21, it
landed 21 seconds after xdg-desktop-portal restarted, and that is one sample and
not a theory. What this buys is that the next one is a two-second blip the
doctor names, rather than three silent days.
Second time for this bug.
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