On Mon, Apr 29, 2019 at 09:26:45AM -0400, Jerome Glisse wrote: > This is a filesystem opt-in feature if a given filesystem do not want > to implement it then just do not implement it and it will use page > cache. It is not mandatory i am not forcing anyone. The first reasons > for those are not filesystem but mmap of device file. But as LSF/MM > is up i thought it would be a good time to maybe propose that for file- > system too. If you do not want that for your filesystem then just NAK > any patch that add that to filesystem you care about. No. This is stupid, broken, and wrong. I know we already have application-visible differences between filesystems, and every single one of those is a bug. They may be hard bugs to fix, they may be bugs that we feel like we can't fix, they may never be fixed. But they are all bugs. Applications should be able to work on any Linux filesystem without having to care what it is. Code has a tendency to far outlive its authors expectations (and indeed sometimes its authors). If 'tar' had an #ifdef XFS / #elsif EXT4 / #elsif BTRFS / ... #endif, that would be awful. We need the same semantics across all major filesystems. Anything else is us making application developers lives harder than necessary, and that's unacceptable.
