On Wed, May 13, 2020 at 6:17 AM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote: > > ---- 在 星期三, 2020-05-13 09:10:19 Eryu Guan <eguan@xxxxxxxxxxxxxxxxx> 撰写 ---- > > 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? > > > > IMO, for those features which don't need to change module param, maybe feature list > is more suitable. > I suppose it is more suitable, but since at the moment there is only one(?) such feature and there is an open question whether it should or should not be configurable, I myself would have taken the easy path, but Miklos often has a different perspective on these sort of things... Thanks, Amir.
