On Wed, Sep 02, 2020 at 08:57:07AM +0200, Miklos Szeredi wrote: > On Tue, Sep 1, 2020 at 10:41 PM Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > > > > FUSE_NONSHARED_FS will signify that filesystem is not shared. That is > > all fuse modifications are going thourgh this single fuse connection. It > > should not happen that file's data/metadata changed without the knowledge > > of fuse. Automatic file time stamp changes will probably be an exception > > to this rule. > > > > If filesystem is shared between different clients, then this flag should > > not be set. > > I'm thinking maybe this flag should force some other parameters as well: So you are thinking of fuse enforcing these parameters automatically without server asking for it. IOW, override what server says about following parameters and fuse sets their values if FUSE_NONSHARED_FS is set? Or should we recommend these for FUSE_NONSHARED_FS and let file server specify all this. > > ^FUSE_POSIX_LOCK No remote posix locks. Makes sense. If filesystem is not shared then there is no need of remote posix locks. > ^FUSE_FLOCK_LOCKS No remote BSD style file locks. If filesystem is not shared, then local locks should work just fine. > ^FUSE_AUTO_INVAL_DATA This controls if page cache data should be invalidated upon mtime change. For non shared fs, mtime should not change outside fuse, so makes sense to enforce ^FUSE_AUTO_INVAL_DATA. > FUSE_EXPLICIT_INVAL_DATA This tells fuse to not invalidate page cache and not truncate page cache if attr->size or mtime change is detected. For non-shared fs we don't expect attr->size or mtime to change, so it does not harm to enfroce this. > FUSE_CACHE_SYMLINKS This caches readlink responses. Makes sense to enable it for non shared fs. > attr_valid=inf > entry_valid=inf dentry and attr timeout being infinite should be good for performance if filesystem is not shared. > FOPEN_KEEP_CACHE If this is not set, by default fuse invalidates page cache on open. Makes sense to not flush page cache on open with FUSE_NONSHARED_FS. > FOPEN_CACHE_DIR Caching directory contents for FUSE_NONSHARED_FS makes sense too. > > This would make sure that it's really only used in the non-shared case. I am little afraid of enforcing this in fuse core because tomorrow somebody will say hey I need hybrid mode where FUSE_NONSHARED_FS is set but for some reason I want attrs to expire after some time. I don't have a good use case in my mind though. If I were to choose, I will probably document it and suggest that file servers sets all the above for the case of FUSE_NONSHARED_FS. But I am also open to enforcing this in fuse core if you prefer that option. Thanks Vivek
