On Mon, Feb 17, 2025 at 01:32:28PM +0000, Luis Henriques wrote: > Currently userspace is able to notify the kernel to invalidate the cache > for an inode. This means that, if all the inodes in a filesystem need to > be invalidated, then userspace needs to iterate through all of them and do > this kernel notification separately. > > This patch adds a new option that allows userspace to invalidate all the > inodes with a single notification operation. In addition to invalidate > all the inodes, it also shrinks the sb dcache. You still haven't justified why we should be exposing this functionality in a low level filesystem ioctl out of sight of the VFS. User driven VFS cache invalidation has long been considered a DOS-in-waiting, hence we don't allow user APIs to invalidate caches like this. This is one of the reasons that /proc/sys/vm/drop_caches requires root access - it's system debug and problem triage functionality, not a production system interface.... Every other situation where filesystems invalidate vfs caches is during mount, remount or unmount operations. Without actually explaining how this functionality is controlled and how user abuse is not possible (e.g. explain the permission model and/or how only root can run this operation), it is not really possible to determine whether we should unconditional allow VFS cache invalidation outside of the existing operation scope.... FInally, given that the VFS can only do best-effort invalidation and won't provide FUSE (or any other filesystem) with any cache invalidation guarantees outside of specific mount and unmount contexts, I'm not convinced that this is actually worth anything... -Dave. -- Dave Chinner david@xxxxxxxxxxxxx
