On Fri, May 9, 2025 at 10:00 PM Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > > On Fri, 9 May 2025 at 08:34, Chen Linxuan via B4 Relay > <devnull+chenlinxuan.uniontech.com@xxxxxxxxxx> wrote: > > > > From: Chen Linxuan <chenlinxuan@xxxxxxxxxxxxx> > > > > Add a new FUSE control file "/sys/fs/fuse/connections/*/backing_files" > > that exposes the paths of all backing files currently being used in > > FUSE mount points. This is particularly valuable for tracking and > > debugging files used in FUSE passthrough mode. > > This is good work, thanks. > > My concern is that this is a very fuse specific interface, even though > the problem is more generic: list hidden open files belonging to a > kernel object, but not installed in any fd: > > - SCM_RIGHTS > - io_uring Note that io_uring has already exposed information about fixed files in its fdinfo. > - fuse > > So we could have a new syscall or set of syscalls for this purpose. > But that again goes against my "this is not generic enough" pet peeve. > > So we had this idea of reusing getxattr and listxattr (or implementing > a new set of syscalls with the same signature) to allow retrieving a > hierarchical set of attributes belonging to a kernel object. This one > would also fit that pattern, so... > > Thoughts? Using getxattr does make it more generalized, and I think reusing it is a good choice. However, I have some questions: If we use getxattr, For io_uring, the path could be the corresponding /proc/PID/fd/* of io_uring. For FUSE, the path could be /sys/fs/fuse/connections/*. But for SCM_RIGHTS, what would the corresponding path be? Could it be the fd under procfs of unix domain socket? I am also uncertain whether there might be similar situations in the future. Would we really be able to find a suitable path for all of them? Thanks, Chen Linxuan > > Thanks, > Miklos > >
