On Tue, Feb 06, 2018 at 03:38:09PM -0800, Eric Biggers wrote: > I don't think backporting this change for other filesystems is particularly > important, since if I understand correctly, the reasons that Al made the change > originally were: > > - to allow following symlinks in RCU mode, but that's not implemented in old > kernels Yup. > - to prevent a process from using up all kmaps and deadlocking the system, which > I'm not sure is a real problem (someone would need to try to put together a > reproducer), but if so it would probably just be a local device of service. .. and *that's* only a problem on 32-bit systems. And aside from Android, it's unclear to me how much we need to support 32-bit systems on upstream LTS kernels. I suppose there might be Rasperry PI's which are 32-bits and which might want to use btrfs. Personally I'm not sure we should care all that much, but others who care more about LTS kernels and 32-bit systems might have a different opinion. > Also if we actually backported the full commit there are follow-on fixes such as > e8ecde25f5e that would be needed as well but might be missed. Good point. - Ted