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b=o09DWJ22Hv5sHflnQ1KniaNaofyCHe2ZxHKC48xizG9lN7TljgWIskyagAIXb1Bfl YC9oZaXML51B5Vh19zrnY46RxqekLzZB4LTnj6+19iR+CcSZYvaN6l0MYN5QrMBoL0 Tsynq4042P+2BCJphiI9H6z36IdoXTreK7b2+694Yoy0yC5oG/THF7LA2lHYPZijgK NtH7OX5WqDi9hbgbxupM4wvzpFZ8o9Ke7Re+gD+O0FPj8ur9kU52Ea+s0kVMDYxBX7 IlXGBs6CPlA8n3BoN/PgXPP0cz7aR9WQH1WlF/ZgNei3MFZE6v5c3FOlvWQlbvfz2J /x/efvJVmWLpQ== Message-ID: <86119f7f-bd70-428e-a6e0-eea7cc907bbe@kernel.org> Date: Thu, 30 Jul 2026 14:47:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] mm/migrate_device: Clear stale mapping after freeing swapcache To: "Yadav, Arvind" , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, ziy@nvidia.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, balbirs@nvidia.com References: <20260728062832.1107127-1-arvind.yadav@intel.com> <8d50f94b-6d95-4967-aa1f-2c14333ffd85@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: B26E340009 X-Stat-Signature: 4xz8fh7dgqdygw9darqqiny9md3myi4e X-HE-Tag: 1785415678-491447 X-HE-Meta: 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 9ipS9Bjw ZRVcoLemJTMQqueGwu4BmAUJjPozgxSxOYymIYSjWaeOo1ofifluC9ASRtabhpa9RAN5PeY2ax1ibb9uDrCH62Y8aEnH8NZo43Myh/pUfvaibHUJHkTLaY8ET6qKkBnA2u8Y3s95MIwJ8CvoxNbRnMW9r+g32Y0EwwcV1M4YDZaS1U4hlrHWdU+of8jFO+MwdUwaMPGZm5e7p6KHT7BRPAFIWja3rsTNIPBDIaeV8RssykfpdXITr3msk48JippbiVMqOZOErStoleRiqcGPqYAQaDKiAhs42QuVPusjkl3OrxAS0OKyEpjY9UiYfa175yiKPr0t+nIYm6vF/1myrmFSB/VM3A8GELUxQiqZ8aek0dKMkNY0lVvqFHFX65/GcsfaV Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >> While this looks good, I do wonder why do we have to supply the mapping here >> at all? >> >> Is there a path where we call folio_migrate_mapping() and the old folio (folio) >> does no longer have the right mapping attached? >> >> It would be a lot less error prone if the function would just obtain the mapping >> from the old folio. > > > Agreed. I will make folio_migrate_mapping() obtain the mapping from the source > folio and update its in-tree callers. Since this changes an exported helper, I > will send it as a separate patch in v5. I think it would be good to understand why we currently pass in the folio: was there ever a reason to do so? Or why do we pass in something that can just easily be had from the source folio? But note that that should be a follow-up cleanup to the fix. -- Cheers, David