On Tue 30-10-12 21:22:38, Tejun Heo wrote:
> 2ef37d3fe4 ("memcg: Simplify mem_cgroup_force_empty_list error
> handling") removed the last user of __DEPRECATED_clear_css_refs. This
> patch removes __DEPRECATED_clear_css_refs and mechanisms to support
> it.
>
> * Conditionals dependent on __DEPRECATED_clear_css_refs removed.
>
> * ->pre_destroy() now can only fail if a new task is attached or child
> cgroup is created while ->pre_destroy()s are being called. As the
> condition is checked again after re-acquiring cgroup_mutex
> afterwards, we don't need to take any immediate action on
> ->pre_destroy() failures. This reduces cgroup_call_pre_destroy() to
> a simple loop surrounding ->pre_destory(). Remove
> cgroup_call_pre_destroy() and open-code the loop into
> cgroup_rmdir().
>
> * cgroup_clear_css_refs() can no longer fail. All that needs to be
> done are deactivating refcnts, setting CSS_REMOVED and putting the
> base reference on each css. Remove cgroup_clear_css_refs() and the
> failure path, and open-code the loops into cgroup_rmdir().
>
> Note that cgroup_rmdir() will see more cleanup soon.
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Looks good to me and the diffstat is really encouraging
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
with a minor note bellow
> ---
> include/linux/cgroup.h | 12 ----
> kernel/cgroup.c | 159 ++++++++++++-------------------------------------
> 2 files changed, 38 insertions(+), 133 deletions(-)
[...]
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 7981850..033bf4b 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
[...]
> @@ -4168,11 +4075,9 @@ again:
> * Call pre_destroy handlers of subsys. Notify subsystems
> * that rmdir() request comes.
> */
> - ret = cgroup_call_pre_destroy(cgrp);
> - if (ret) {
> - clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
> - return ret;
> - }
> + for_each_subsys(cgrp->root, ss)
> + if (ss->pre_destroy)
> + WARN_ON_ONCE(ss->pre_destroy(cgrp));
Hmm, I am not sure I like this WARN_ON_ONCE. First it can happen for
more than one controller and second we can just clear CGRP_WAIT_ON_RMDIR
and return with EBUSY. The only possible failure at the moment is when a
new task or a child group appear.
I know it is not a big deal because it will disappear later in the
series but it would be more readable IMO.
Thanks!
--
Michal Hocko
SUSE Labs
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