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From: Zi Yan <ziy@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org,
 "\"Pankaj Raghav (Samsung)\"" <kernel@pankajraghav.com>,
 Zi Yan <ziy@nvidia.com>, "\"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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 Luis Chamberlain <mcgrof@kernel.org>, linux-kernel@vger.kernel.org,
 cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org,
 linux-kselftest@vger.kernel.org, Dan Carpenter <dan.carpenter@linaro.org>
Subject: Re: [PATCH v5 8/8] mm: huge_memory: enable debugfs to split huge
 pages to any order.
Date: Thu, 07 Mar 2024 10:06:48 -0500
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On 26 Feb 2024, at 15:55, Zi Yan wrote:

> From: Zi Yan <ziy@nvidia.com>
>
> It is used to test split_huge_page_to_list_to_order for pagecache THPs.=

> Also add test cases for split_huge_page_to_list_to_order via both
> debugfs.
>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>  mm/huge_memory.c                              |  34 ++++--
>  .../selftests/mm/split_huge_page_test.c       | 115 +++++++++++++++++-=

>  2 files changed, 131 insertions(+), 18 deletions(-)

Hi Andrew,

This is the fixup for patch 8. It is based on the discussion
with Dan Carpenter at https://lore.kernel.org/linux-mm/7dda9283-b437-4cf8=
-ab0d-83c330deb9c0@moroto.mountain/. It checks new_order input from
debugfs and skips folios early if new_order is greater than the folio ord=
er.

Thanks.

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a81a09236c16..42d4f62d7760 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3484,6 +3484,9 @@ static int split_huge_pages_pid(int pid, unsigned l=
ong vaddr_start,
                        goto next;

                total++;
+
+               if (new_order >=3D folio_order(folio))
+                       goto next;
                /*
                 * For folios with private, split_huge_page_to_list_to_or=
der()
                 * will try to drop it before split and then check if the=
 folio
@@ -3550,6 +3553,9 @@ static int split_huge_pages_in_file(const char *fil=
e_path, pgoff_t off_start,
                total++;
                nr_pages =3D folio_nr_pages(folio);

+               if (new_order >=3D folio_order(folio))
+                       goto next;
+
                if (!folio_trylock(folio))
                        goto next;


--
Best Regards,
Yan, Zi

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