On Tue, May 12, 2020 at 07:56:35PM +0300, Amir Goldstein wrote: > > > > I see no feature detection logic, so test just fails on old kernels > > > > without this feature? I tried with v5.7-r4 kernel, test fails because > > > > each whiteout file has only one hardlink. > > > > > > That's true. > > > > I'd like to see it _notrun on old kernels where the feature is not > > available. But that seems hard to do.. Do you have any better ideas? > > > > I've got a few. > 1. LTP has the concept of require minimum kernel version. > This would mean that functionality will be not be tested if feature > is backported to old kernels. > 2. We could add to overlayfs advertising of supported features, like > /sys/fs/ext4/features/, but it already does "advertise" the configurable > features at /sys/module/overlay/parameters/, and we were already > asking the question during patch review: > /* Is there a reason anyone would want not to share whiteouts? */ > ofs->share_whiteout = true; > and we left the answer to "later" time. > > So a simple solution would be to add the module parameter (without adding > a mount option), because: > - It doesn't hurt (?) > - Somebody may end up using it, for some reason we did not think of > - We can use it in test to require the feature Yeah, I think that works. And I see that ext4 and btrfs both have a /sys/fs/<fs>/features directory and list supported features there, is this something overlay could do? Or is this basically the same thing as what you proposed? Thanks, Eryu > > The one non-trivial thing that this will require is to add Documentation > of the module parameter in the section about Whiteouts and opaque directories. > > Thanks, > Amir.
