On Sun 14-06-15 00:42:36, Tejun Heo wrote:

Hello, Christoph.

On Sat, Jun 13, 2015 at 09:16:08AM -0700, Christoph Hellwig wrote:

quoted

On Fri, Jun 12, 2015 at 04:57:33PM -0500, Tejun Heo wrote:

quoted

FS_CGROUP_WRITEBACK indicates whether a file_system_type supports
cgroup writeback; however, different super_blocks of the same
file_system_type may or may not support cgroup writeback depending on
filesystem options.  This patch replaces FS_CGROUP_WRITEBACK with a
kernel-internal super_block->s_flags MS_CGROUPWB.  The concatenated
and abbreviated name is for consistency with other MS_* flags.

Nak.  As the uapi part makes it obvious the MS_ namespace is part
of the userspace ABI.  Please add a new in-kernel flags field instead.

Are MS_ACTIVE and MS_BORN part of userpace ABI?  They seem pretty
internal.  I don't mind introducing a new internal flag field but it's
weird to put this single flag there with other internal flags in
->s_flags.

  So you are right that there are other internal flags allocated from the
top of the i_flags field, however we are pretty much running out of the
flags available for the ABI so it's better to move internal flags elsewhere
as that's simpler than creating a new ABI for mount...

Assuming we add a new field, how do sb->s_iflags and SB_I_XXX sound?
Any better suggestions?

  Looks good to me.

								Honza
-- 
Jan Kara [off-list ref]
SUSE Labs, CR