linux-kernel - Re: [PATCH 1/2] fs: fsnotify: account fsnotify metadata to kmemcg

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Message-ID: <20180626185724.GA3958@cmpxchg.org>
Date:   Tue, 26 Jun 2018 14:57:24 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Amir Goldstein <amir73il@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Jan Kara <jack@...e.com>, Greg Thelen <gthelen@...gle.com>,
        Roman Gushchin <guro@...com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        Cgroups <cgroups@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH 1/2] fs: fsnotify: account fsnotify metadata to kmemcg

On Tue, Jun 26, 2018 at 11:00:53AM -0700, Shakeel Butt wrote:
> On Mon, Jun 25, 2018 at 10:49 PM Amir Goldstein <amir73il@...il.com> wrote:
> >
> ...
> >
> > The verb 'unuse' takes an argument memcg and 'uses' it - too weird.
> > You can use 'override'/'revert' verbs like override_creds or just call
> > memalloc_use_memcg(old_memcg) since there is no reference taken
> > anyway in use_memcg and no reference released in unuse_memcg.
> >
> > Otherwise looks good to me.
> >
> 
> Thanks for your feedback. Just using memalloc_use_memcg(old_memcg) and
> ignoring the return seems more simple. I will wait for feedback from
> other before changing anything.

We're not nesting calls to memalloc_use_memcg(), right? So we don't
have to return old_memcg and don't have to pass anything to unuse, it
can always set current->active_memcg to NULL.