On Thu, 2021-10-21 at 18:15 -0500, Steve French wrote: > On Thu, Oct 21, 2021 at 5:21 PM Omar Sandoval <osandov@xxxxxxxxxxx> wrote: > > > > On Mon, Oct 18, 2021 at 03:50:15PM +0100, David Howells wrote: > > However, with the advent of the tmpfile capacity in the VFS, an opportunity > > arises to do invalidation much more easily, without having to wait for I/O > > that's actually in progress: Cachefiles can simply cut over its file > > pointer for the backing object attached to a cookie and abandon the > > in-progress I/O, dismissing it upon completion. > > Have changes been made to O_TMPFILE? It is problematic for network filesystems > because it is not an atomic operation, and would be great if it were possible > to create a tmpfile and open it atomically (at the file system level). > > Currently it results in creating a tmpfile (which results in > opencreate then close) > immediately followed by reopening the tmpfile which is somewhat counter to > the whole idea of a tmpfile (ie that it is deleted when closed) since > the syscall results > in two opens ie open(create)/close/open/close > > In this case, O_TMPFILE is being used on the cachefiles backing store, and that usually isn't deployed on a netfs. That said, Steve does have a good point... What happens if you do end up without O_TMPFILE support on the backing store? Probably just opting to not cache in that case is fine. Does cachefiles just shut down in that situation? -- Jeff Layton <jlayton@xxxxxxxxxx>
