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h=Date:From:To:Subject:In-Reply-To:References; b=hMOtHPnze4qedvrdjm0cpkZabhZxEXLK4VPdmuyNtKV4pc/tLykmuM5sdH94rcq4+ m3iaEQRJv/0Luv7TMWuXSMzR9ps5wi7Kq8U9wuhf+ebhR0Ubs/63mlDYYo9/Ro0CWx WOLv7oHaIMQu+v5N8oZOHkGfdvOaQRwtyowf6ctc= Date: Mon, 17 Aug 2026 15:12:04 -0700 From: Andrew Morton To: Hui Su , apopple@nvidia.com, balbirs@nvidia.com, byungchul@sk.com, david@kernel.org, gourry@gourry.net, joshua.hahnjy@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, matthew.brost@intel.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com, ziy@nvidia.com Subject: Re: [PATCH] mm/migrate_device: fix cache flush when replacing huge zero PMD Message-Id: <20260817151204.50749d6a3e16e322e6f05d7d@linux-foundation.org> In-Reply-To: <20260817143415.60bedb09819d13a2dc0fbe63@linux-foundation.org> References: <20260817090640.287a9a415da49e3974797aa4@linux-foundation.org> <20260817163646.929678-1-sh_def@163.com> <20260817143415.60bedb09819d13a2dc0fbe63@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: B5EF6C0008 X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: grqbzdb5xfentjqfdsea7wn4u455ctus X-HE-Tag: 1787004725-649015 X-HE-Meta: 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 t0Xe0w37 fELVeaGtPq4aEA8OQ+rlcwWCmkJQOi0hjxwP6cy2akWSyYB7lKiiRPfQNSCnOjETWhIRNh8RiAtXURb1GIRhHRw6FOuSN3Q+RO5PkxOGHXl6EK/NEITQj8ZzB9SmDtxPORDi0BNlo0wsrbSt9sLjySfNEHEkx/8Ol+WdNC19jDgBJIUGuYA516kPSsVSdT1ttafl07PxdeVWloXY+HASXdXQAX68/12bWKfy4K1s9M/GCM9U0hfiNCr+334QCHRk6LETfQUXjTV1s1Mwnwov2vn3cGeo9A/tc4ilQfzKhjNO5U7vIYcDtDw23bua6f2gpH08/0MOQPiMcN+IfCv6lvq8neNNSYTlerzUqydn8upB3tBmGt+AAXn6IVoFY4+wPFeeaL792yN8Nym2/chSvHvRtuNRc6a1On1cWQotHWaobEtLVjy0HAtpan+aty3cOpV/D47xjUmDYEYE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 17 Aug 2026 14:34:15 -0700 Andrew Morton wrote: > > Hi, > > > > I took a closer look at this, there is no userspace-visible effect today. > > > > The architectures that currently enable ARCH_ENABLE_THP_MIGRATION use > > no-op implementations of flush_cache_page()/flush_cache_range(). > > 32-bit ARM has non-trivial implementations, but does not enable > > ARCH_ENABLE_THP_MIGRATION. > > > > So this appears to be a latent API misuse rather than a currently > > observable bug, and I don't think a stable backport is necessary. > > OK, thanks for checking. > > > Should I resend a v2 clarifying the userspace-visible effect in the > > changelog? > > Yes please, after 7.3-rc1. Actually, I updated the changelog and added it to next week's queue-for-Linus.