xdg-document-portal leaks FDs

[felinira]

Closing an app while having open files causes those FDs to leak.

Steps to reproduce:

• Open amberol for example, select a file to play
• Press Ctrl+q
• Look at lsof -p $(pidof xdg-document-portal)

The file that was opened is still being held open, in contrast to when the app closes the file by itself (eg. by switching to the next track)

[Redecorating]

Seems related to #689, where having these files kept open makes it impossible to unmount filesystems

[xioren]

I have done a little poking around to see if I could learn more about it. One thing I will note is that not all Flatpak apps cause this issue. For me the issue is with MPV, other apps such as my image viewer do not cause an issue. I'm hoping for more discussion on this as it is a particularly egregious imo

[rusty-snake]

Guess because your image viewer has filesystem= permission and dies not usw Portals.

[xioren]

You're probably right. I don't know who on the dev team needs to be made aware of this but we need to be moving mountains to fix this. It has been a problem since at least 2021 and it doesn't seem like any attempt has been made to address what is from my perspective a five alarm fire bug. I have looked through the source code but I don't know C that well and I haven't seen anything obvious that stands out. Here are some other threads with discussions: #4303, #689, #994, #902, #721.

[xioren]

@GeorgesStavracas can you provide some insight? For the methods contained in org.freedesktop.portal.Documents, those are to be called by the program wishing to use xdg-document-portal correct? If so then each program would need to specify whether they want a file for a session or indefinitely by using the persistent argument.

IN h o_path_fd:
open file descriptor for the file to add

IN b reuse_existing:
whether to reuse an existing document store entry for the file

IN b persistent:
whether to add the file only for this session or permanently

OUT s doc_id:
the ID of the file in the document store

I'm trying to piggy back off what @teohhanhui referenced in #4303. In my case every time I open a file, a new export shows up in /run/user/$UID/doc/. So right now I have five exports and counting for the same file in the MPV directory, and they stay there even after closing the flatpak. I'm trying to figure out if that's normal behavior.

[GeorgesStavracas]

Duplicate of #689