On Thu, 2021-10-21 at 18:15 -0500, Steve French wrote:

On Thu, Oct 21, 2021 at 5:21 PM Omar Sandoval [off-list ref] wrote:

quoted

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 [off-list ref]