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	Mon, 24 Jun 2024 18:56:20 +0000
Date: Mon, 24 Jun 2024 19:56:20 +0100
From: Matthew Wilcox <willy@infradead.org>
To: Yosry Ahmed <yosryahmed@google.com>
Cc: kernel test robot <oliver.sang@intel.com>,
	Usama Arif <usamaarif642@gmail.com>, oe-lkp@lists.linux.dev,
	lkp@intel.com, Linux Memory Management List <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Chengming Zhou <chengming.zhou@linux.dev>,
	Nhat Pham <nphamcs@gmail.com>, David Hildenbrand <david@redhat.com>,
	"Huang, Ying" <ying.huang@intel.com>,
	Hugh Dickins <hughd@google.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Shakeel Butt <shakeel.butt@linux.dev>,
	Andi Kleen <ak@linux.intel.com>, linux-kernel@vger.kernel.org
Subject: Re: [linux-next:master] [mm] 0fa2857d23:
 WARNING:at_mm/page_alloc.c:#__alloc_pages_noprof
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 <CAJD7tkbqHyNUzQg_Qh+-ZryrKtMzdf5RE-ndT+4iURTqEo3o6A@mail.gmail.com>
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On Mon, Jun 24, 2024 at 11:53:30AM -0700, Yosry Ahmed wrote:
> After a page is swapped out during reclaim, __remove_mapping() will
> call __delete_from_swap_cache() to replace the swap cache entry with a
> shadow entry (which is an xa_value).

Special entries are disjoint from shadow entries.  Shadow entries have
the last two bits as 01 or 11 (are congruent to 1 or 3 modulo 4).
Special entries have values below 4096 which end in 10 (are congruent
to 2 modulo 4).