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From: Zi Yan <ziy@nvidia.com>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: "\"Pankaj Raghav (Samsung)\"" <kernel@pankajraghav.com>,
 linux-mm@kvack.org, "\"Matthew Wilcox (Oracle)\"" <willy@infradead.org>,
 David Hildenbrand <david@redhat.com>, Yang Shi <shy828301@gmail.com>,
 Yu Zhao <yuzhao@google.com>,
 "\"Kirill A . Shutemov\"" <kirill.shutemov@linux.intel.com>,
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 Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
 cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org,
 linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v4 5/7] mm: thp: split huge page to any lower order pages
 (except order-1).
Date: Tue, 13 Feb 2024 17:15:08 -0500
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Content-Type: text/plain

On 13 Feb 2024, at 17:05, Luis Chamberlain wrote:

> On Tue, Feb 13, 2024 at 04:55:18PM -0500, Zi Yan wrote:
>> From: Zi Yan <ziy@nvidia.com>
>> Order-1 folio is not supported because _deferred_list, which is used by
>> partially mapped folios, is stored in subpage 2 and an order-1 folio only
>> has subpage 0 and 1.
>
> The LBS patches has the patch from Matthew which enables and allowed us
> to successfully test order 1. So this restriction could be dropped if
> that gets merged.

OK. But it only applies to file-backed folios IIUC. Anonymous folios still
cannot be split to order-1.

--
Best Regards,
Yan, Zi

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