From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5CF738BE9 for ; Tue, 23 Jun 2026 11:50:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782215402; cv=none; b=EhjcG89Y7FrWdatUHIXg/jWSb8dqP8Qao+YjtPtl2NPTBs7suOufAHdEsWFobZSK6f4LKWylgmcxg9auK0zb0+1JnN4RkAZTeTgS+E4c633lTjR4qPJxfiq6ZbZL8F4zeSgkFjJb0s92hTBhB3qlbcGMI/9/undNEDJQPUqpBvk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782215402; c=relaxed/simple; bh=BjBsTgILT19ndrP6qZuJZ9xPzWyLNxLCYIs+PgtAJME=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VbMpwG41odkfWde+z7pFRiAt5N5dQj0jJ8FxPHArA3bxX6mFdL1QCIabqw6b7nZFnu2ymwm0xaguyxYx07QoDMnRHK+ZLYPwqD7kh2BHl3AwCxwdook7jIg33bVELAYfIStisPfoU+kV3YmHmfcSybXfyXYFOgRAnhVJInjVK08= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b/jvcnkx; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="b/jvcnkx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FEB51F000E9; Tue, 23 Jun 2026 11:49:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782215401; bh=n90/FCvkfLh5mKq5gig+7rKJkhz1HQOD5cIteVuMxhY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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