On Wed, Feb 28, 2024 at 5:01 PM Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > > On Wed, 28 Feb 2024 at 15:32, Jens Axboe <axboe@xxxxxxxxx> wrote: > > > > On 2/28/24 4:28 AM, Amir Goldstein wrote: > > > > Are fixed files visible to lsof? > > > > lsof won't show them, but you can read the fdinfo of the io_uring fd to > > see them. Would probably be possible to make lsof find and show them > > too, but haven't looked into that. > > Okay, that approach could be used with fuse as well. This isn't > perfect, but we can think improving the interface for both. > > > > Do they get accounted in rlimit? of which user? > > > > The fixed file table is limited in size by RLIMIT_NOFILE by the user > > that registers it. > > That's different for fuse as the server wouldn't register the whole > file table in one go. The number of used slots could be limited by > RLIMIT_NOFILE, I think. > Yes. We can limit the number of backing id slots, which is the number of FUSE_DEV_IOC_BACKING_OPEN for whom the server did not call FUSE_DEV_IOC_BACKING_CLOSE, and we can easily display the backing files in backing_files_map, but we also have inode attached backing file, whose lifetime is that of the fuse files. Those all harder to iterate and harder to limit, because the server cannot close/revoke them. OTOH, we could treat the inode attached backing files same as the overlayfs backing files - worst case they only double the number of files in the system. We can probably keep them also in backing_files_map so we can iterate them, but maybe let's see how the basic feature works first... Thanks, Amir.
