User extended attributes are useful as metadata storage for kernfs consumers like cgroups. Especially in the case of cgroups, it is useful to have a central metadata store that multiple processes/services can use to coordinate actions. A concrete example is for userspace out of memory killers. We want to let delegated cgroup subtree owners (running as non-root) to be able to say "please avoid killing this cgroup". In server environments this is less important as everyone is running as root. But for desktop linux, this is more important. The first patch introduces a new flag, KERNFS_ROOT_SUPPORT_USER_XATTR, that lets kernfs consumers enable user xattr support. The second patch turns on this feature for cgroupfs. Daniel Xu (2): kernfs: Add option to enable user xattrs cgroupfs: Support user xattrs fs/kernfs/inode.c | 47 +++++++++++++++++++++++++++++++++++++ fs/kernfs/kernfs-internal.h | 1 + include/linux/kernfs.h | 6 +++++ kernel/cgroup/cgroup.c | 3 ++- 4 files changed, 56 insertions(+), 1 deletion(-) -- 2.21.1
