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Date: Tue, 1 Sep 2026 09:06:19 +0100
From: Yeoreum Yun <yeoreum.yun@arm.com>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Yeoreum Yun <yeoreum.yun@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@kernel.org>,
	Lorenzo Stoakes <ljs@kernel.org>, Zi Yan <ziy@nvidia.com>,
	"Liam R. Howlett" <liam@infradead.org>,
	Nico Pache <nico.pache@linux.dev>,
	Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
	Barry Song <baohua@kernel.org>, Lance Yang <lance.yang@linux.dev>,
	Usama Arif <usama.arif@linux.dev>,
	Vlastimil Babka <vbabka@kernel.org>,
	Mike Rapoport <rppt@kernel.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Michal Hocko <mhocko@suse.com>, Shuah Khan <shuah@kernel.org>,
	Kevin Brodsky <kevin.brodsky@arm.com>, linux-mm@kvack.org,
	linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/2] kselftest: mm: replace usage of /proc/self/smaps
 for check_huge_xxx() helper
Message-ID: <apaHexgq0pYduNq8@e129823.arm.com>
References: <20260828-fix_split-v3-0-374022586a4b@arm.com>
 <20260828-fix_split-v3-2-374022586a4b@arm.com>
 <f9ae614f-beef-4e83-b307-d4e743d7062c@linux.alibaba.com>
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In-Reply-To: <f9ae614f-beef-4e83-b307-d4e743d7062c@linux.alibaba.com>

On Mon, Aug 31, 2026 at 03:58:18PM +0800, Baolin Wang wrote:
> 
> 
> On 8/28/26 4:11 PM, Yeoreum Yun wrote:
> > Since glibc commit 321e1fc73f (“malloc: Enable 2MB THP by default on AArch64”),
> > glibc may call madvise(MADV_HUGEPAGE) for sufficiently large allocations
> > made by memalign().
> > 
> > The underlying VMA may start at a different address from the aligned
> > address returned by memalign(). Furthermore, a subsequent
> > madvise(MADV_HUGEPAGE) call does not split the VMA because the flag is
> > already set.
> > 
> > This causes split_huge_page_test to fail because the check_huge_xxx()
> > helpers incorrectly require the address returned by memalign() to
> > match the VMA start address reported in /proc/self/smaps.
> > 
> > Fix this by using /proc/self/pagemap and /proc/kpageflags instead of
> > /proc/self/smaps to detect huge pages.
> > 
> > Reported-by: David Hildenbrand (Arm) <david@kernel.org>
> > Suggested-by: Zi Yan <ziy@nvidia.com>
> > Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> > ---
> 
> LGTM, with comments from Lorenzo and Zi addressed.
> 
> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>

Thanks!

-- 
Sincerely,
Yeoreum Yun