APPLIED[Unstable]: [SRU][UNSTABLE/BIONIC/XENIAL][PATCH] UBUNTU: SAUCE: shiftfs: remove custom tmpfile method

[Seth Forshee]

On Tue, Apr 14, 2020 at 10:17:37PM +0200, Christian Brauner wrote:
> BugLink: https://bugs.launchpad.net/bugs/1872757
> 
> Our revalidate methods were very opinionated about whether or not a
> dentry was valid when we really should've just let the underlay tell us
> what's what. This has led to bugs where a ESTALE was returned for e.g.
> temporary files that were created and directly re-opened afterwards
> through /proc/<pid>/fd/<nr-of-deleted-file>. When a file is re-opened
> through /proc/<pid>/fd/<nr> LOOKUP_JUMP is set and the vfs will
> revalidate via d_weak_revalidate(). Since the file has been unhashed or
> even already gone negative we'd fail the open when we should've
> succeeded.
> 
> I had also foolishly provided a .tmpfile method which so far only has
> caused us trouble and which was involved in the ESTALE problem. If we
> really need this then we can reimplement it properly but I doubt it.
> Remove it for now.
> 
> Reported-by: Christian Kellner <ckellner at redhat.com>
> Reported-by: Evgeny Vereshchagin >evvers at ya.ru>
> Cc: Seth Forshee <seth.forshee at canonical.com>
> Link: https://github.com/systemd/systemd/issues/14861
> Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>

Applied to unstable/master, thanks!