Re: [PATCH 3/7] memcg: remove test for current->mm in memcg_stop/resume_kmem_account

[Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

(2012/11/15 11:54), Glauber Costa wrote:
> The original reason for the existence of this test, was that
> memcg_kmem_cache_create could be called from either softirq context
> (where memcg_stop/resume_account is not needed), or process context,
> (where memcg_stop/resume_account is needed). Just skipping it
> in-function was the cleanest way to merge both behaviors. The reason for
> that is that we would try to create caches right away through
> memcg_kmem_cache_create if the context would allow us to.
> 
> However, the final version of the code that merged did not have this
> behavior and we always queue up new cache creation. Thus, instead of a
> comment explaining why current->mm test is needed, my proposal in this
> patch is to remove memcg_stop/resume_account from the worker thread and
> make sure all callers have a valid mm context.
> 
> Signed-off-by: Glauber Costa <glommer@parallels.com>
> CC: Michal Hocko <mhocko@suse.cz>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> CC: Johannes Weiner <hannes@cmpxchg.org>
> CC: Andrew Morton <akpm@linux-foundation.org>

seems ok to me. But do we need VM_BUG_ON() ?
It seems functions called under memcg_stop_kmem_account() doesn't access
current->mm...

Anyway.
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>