From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 224AC403B10 for ; Mon, 13 Jul 2026 12:12:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783944727; cv=none; b=HBL5IfsU0YD9ASh+AUCWXOBkd2tLP7Ox4Z04RKIw3ROlcF2bOlYCCR0QwyXKT5lVyUey/vvXVIkT0qXdrev/WmdTTztdHMR3koVn1s50AbD9LHYtZPnCvErzrYM4PihXVxnKNKRuMF0+o7BfSTWIyMDmZmCvJGaGsIwMJR+NMGo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783944727; c=relaxed/simple; bh=XybwoLlYtcu13ujCRHeQdo4p5ZZ7uLYbhY79oGKMjBM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZmkDDsZsdeXLkWx57jDxTewXENoBgFv7l43hsDs3Mwj7FFUi/ugRquLMlZwdJIenyaz25jokmniDYPE8R22+penKNMVqvr/HcXvWcLyKxFrmT7WpYbRAFiE9GuHm+H5JoNVAdJum8Mf5o2YOl6xsVnaxhA/ew78LhTHtrfwdNNs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=I4r31t5F; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="I4r31t5F" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BC7AA1576; Mon, 13 Jul 2026 05:11:59 -0700 (PDT) Received: from [10.164.19.52] (unknown [10.164.19.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2ED133F93E; Mon, 13 Jul 2026 05:11:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783944724; bh=XybwoLlYtcu13ujCRHeQdo4p5ZZ7uLYbhY79oGKMjBM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=I4r31t5FDkY2Ahd5+cnL3anhmAw4hSrrFiuA00uPSP3uMe14XaFKKAu3bMN0+22ox QcJ2h3zFqhmePduDEtgmoY2An4UNohHvjD2Ag5kyl54FgvTOtBFYddEQ1WneVu6G4q SPOck9PQRA68LO772OTnP4LXJ13OYkeXzCk6GdZw= Message-ID: Date: Mon, 13 Jul 2026 17:41:57 +0530 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 v2 2/5] mm/rmap: Add try_to_unmap_hugetlb_one To: "David Hildenbrand (Arm)" , akpm@linux-foundation.org, ljs@kernel.org, muchun.song@linux.dev, osalvador@suse.de Cc: riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260710055915.638659-1-dev.jain@arm.com> <20260710055915.638659-3-dev.jain@arm.com> <49b408b9-6d10-4892-916f-ad8e7ef875e5@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 13/07/26 4:04 pm, David Hildenbrand (Arm) wrote: > On 7/10/26 15:16, Dev Jain wrote: >> >> >> On 10/07/26 11:29 am, Dev Jain wrote: >>> Simplify try_to_unmap_one() by separating 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. >>> >>> 2. A hugetlb VMA cannot be mlocked. >>> >>> 3. page_vma_mapped_walk() returns at most one hugetlb mapping in a VMA, >>> and that mapping points at the head PFN. >>> >>> 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. >>> >>> 5. The hwpoison entry is constructed from the poisoned folio, just as in >>> the pre-refactor code. Any previous uffd-wp state is deliberately not >>> preserved for the hwpoison entry. >>> >>> 6. TTU_HWPOISON is always present; for it to not be present, either the >>> folio has to be in swapcache, or mapping_can_writeback() is true (see >>> unmap_poisoned_folio), none of which is true for hugetlb folios. >>> >>> 7. Hugetlb uses separate counters from normal rss counters, therefore >>> update_highwater_rss() need not be called. >>> >>> While at it: >>> >>> - Change VM_BUG_* to VM_WARN_*. >>> >>> - Do not declare variables which are only used once. >>> >>> - Constify some variables. >>> >>> - Add some more VM_WARN_* to assert some invariants. >>> >>> Except the above 4 points, no functional change intended. >>> >>> Suggested-by: David Hildenbrand (Arm) >>> Acked-by: David Hildenbrand (Arm) >>> Signed-off-by: Dev Jain >>> --- >> >> Andrew, could you squash the following diff: >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index cf02b315a2ead..b61051b879c4c 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -2229,8 +2229,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, >> update_hiwater_rss(mm); >> >> /* >> - * With TTU_HWPOISON, we only expect small folios or hugetlb >> - * folios here for now. >> + * With TTU_HWPOISON, we only expect small folios here. >> */ >> if (folio_test_hwpoison(folio) && (flags & TTU_HWPOISON)) { >> pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); > > Note that the comment likely fits into a single line now. Yes, took care of that in v3 :) >