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Date: Mon, 14 Oct 2024 16:27:30 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Wei Xu <weixugc@google.com>
Cc: Yu Zhao <yuzhao@google.com>, Brian Geffon <bgeffon@google.com>, Jan
 Alexander Steffens <heftig@archlinux.org>, Suleiman Souhlal
 <suleiman@google.com>, Axel Rasmussen <axelrasmussen@google.com>,
 linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] mm/mglru: reset page lru tier bits when activating
Message-Id: <20241014162730.fc48f2a53b89639a6207ba9d@linux-foundation.org>
In-Reply-To: <20241014221231.832959-1-weixugc@google.com>
References: <20241014221231.832959-1-weixugc@google.com>
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On Mon, 14 Oct 2024 22:12:31 +0000 Wei Xu <weixugc@google.com> wrote:

> folio_activate() calls lru_gen_add_folio() to move the folio to the
> youngest generation.  But unlike folio_update_gen()/folio_inc_gen(),
> lru_gen_add_folio() doesn't reset the folio lru tier bits
> (LRU_REFS_MASK | LRU_REFS_FLAGS).  Fix this inconsistency in
> lru_gen_add_folio() when activating a folio.

What are the runtime effects of this flaw?