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b=b/jvcnkxcsYb8OCiXUklf4q+V6hHfrFnC2A5w8Cmf/D8R6/Y1ZUQq348w6dAC4Koa MAXt3v9fxMPN0+afjplSrUMN7za/UhNPgrcqXAKMdL+6heEUWRsLm0pNKsdTuUxXYi qQp2Br1Oxoh2fNjER1hiGe20qjKx8p0vQZ99vHt7B1MX48l4GkwYOeRN3EwZ/1ZBCk kLno+hQOmhzCZiuvy1vEQNPSZoVDTR7zgNEETk5c0495fyG5EuUvGITr8/UWHzzbcc GjqRoUFZhikwdOT9zUejhpkWFYvCeq8IjUEG3s38ldxaEzRwv58jnXDkbqlNOzD6XB WrZI5OMSeOiWw== Message-ID: <1ee68304-4e86-4519-93ea-d31ab5ee5bff@kernel.org> Date: Tue, 23 Jun 2026 13:49:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 02/12] mm/rmap: Add try_to_unmap_hugetlb_one To: Dev Jain , akpm@linux-foundation.org, ljs@kernel.org, chrisl@kernel.org, kasong@tencent.com, hughd@google.com, liam@infradead.org Cc: riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, baolin.wang@linux.alibaba.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260526063635.61721-1-dev.jain@arm.com> <20260526063635.61721-3-dev.jain@arm.com> <6a85489f-8b26-4c4b-8333-38f8ae1b680a@arm.com> 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-Stat-Signature: e1wumo9fmt6p4zrfiqytqpgt78b3zfx1 X-Rspam-User: X-Rspamd-Queue-Id: 0182C16000F X-Rspamd-Server: rspam02 X-HE-Tag: 1782215401-806452 X-HE-Meta: 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 rHcD26WJ Qpj4F8vaJDjNPtdHL2/mDgluaNWWLirytDOfgg3enctBvKIcrx+cgJoaMqIWm88NzLzVdt2uGvuvLAaRtyDtRSkFLeJ2EcMWtm+yn2702FWlTzQDq2DYfYss5uJDsRgwa45650k+WgIuvj6QHYQ8HU/MnWnja+H3kJgapw2t1uH2ulJatQkR8TFN12IzsQ4RV4LdQi7Nsa4cwgZhvGhXNmPykfgdX4WMgEYo+9pesIWKa1ZgLTvt16Ri0qbSmBpaK/EyTPc0VZQFig05SrO/tOvwY1vN8D330v1zfpbYJ7ihHllHOuXrXt/6Vsw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/23/26 10:40, Dev Jain wrote: > > > On 09/06/26 7:46 pm, David Hildenbrand (Arm) wrote: >> On 5/26/26 08:36, Dev Jain wrote: >>> Simplify try_to_unmap_one by separating out the hugetlb parts into >>> try_to_unmap_hugetlb_one. >>> >>> To understand the correctness of the refactoring, the following points >>> are noted: >>> >>> 1. try_to_unmap() is called for hugetlb folios only when they are >>> hwpoisoned. >> >> Ack >> >>> >>> 2. A hugetlb VMA cannot be mlocked. >> >> Ack >> >>> >>> 3. The pvmw API sets pvmw.pte to the base of the hugetlb folio (pvmw.pmd >>> is NULL). >> >> Ack >> >>> >>> 4. We won't ever process a softleaf entry that encodes a hugetlb folio; >>> hugetlb folios are never swapped out, migration entries will be skipped >>> (PVMW_MIGRATION not passed) and device-exclusive does not work for >>> hugetlb. >> >> Ack, we should always find present entries. >> >>> >>> 5. uffd-wp bit is lost when converting pvmw.pte to hwpoison softleaf >>> (therefore no need to call pte_install_uffd_wp_if_needed after >>> clearing pvmw.pte) >> >> Are you sure? And if so, can you elaborate why + document? > > If you see the current code, we construct pteval from the subpage, losing any > bit state of the previous entry. Also it doesn't make sense anyways to keep > uffd-wp for an hwpoisoned entry. Ah, yes, makes sense. For some reason I confused hugetlb with hwpoison here ... so yeah, this is good. -- Cheers, David