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Message-ID: <ZxoQhEPXmSkM7sH_@tiehlicka>
Date: Thu, 24 Oct 2024 11:16:52 +0200
From: Michal Hocko <mhocko@...e.com>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Johannes Weiner <hannes@...xchg.org>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Muchun Song <muchun.song@...ux.dev>,
Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
Meta kernel team <kernel-team@...a.com>
Subject: Re: [RFC PATCH 3/3] memcg-v1: remove memcg move locking code
On Wed 23-10-24 23:57:12, Shakeel Butt wrote:
> The memcg v1's charge move feature has been deprecated. There is no need
> to have any locking or protection against the moving charge. Let's
> proceed to remove all the locking code related to charge moving.
>
> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> ---
> -/**
> - * folio_memcg_lock - Bind a folio to its memcg.
> - * @folio: The folio.
> - *
> - * This function prevents unlocked LRU folios from being moved to
> - * another cgroup.
> - *
> - * It ensures lifetime of the bound memcg. The caller is responsible
> - * for the lifetime of the folio.
> - */
> -void folio_memcg_lock(struct folio *folio)
> -{
> - struct mem_cgroup *memcg;
> - unsigned long flags;
> -
> - /*
> - * The RCU lock is held throughout the transaction. The fast
> - * path can get away without acquiring the memcg->move_lock
> - * because page moving starts with an RCU grace period.
> - */
> - rcu_read_lock();
Is it safe to remove the implicit RCU?
--
Michal Hocko
SUSE Labs
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