From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f41.google.com (mail-wr1-f41.google.com [209.85.221.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A429F221DAE for ; Sun, 28 Sep 2025 04:49:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759034965; cv=none; b=C3erqtmIh6jmZFsPe+CnCjek3rnxSWCJ20bIorH9u3l4htFEuQYvg6Lu2XG/w6UP6a4Pj8+ej0Zz8KuanhjKqB9rhcrgkHaD0ry9SxvZ6rMmJHJAT7Bo2O2cOYjHud24L/yc6ydpzLN01GXhdtwFT/t4B1gH92BBzA+kKe9aOFs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759034965; c=relaxed/simple; bh=3JXHdTFd0Do4NsJQmtnD90PGDnc76HJueRPgFM3FauY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=NqUJcUaR2TGFj7F4fIyZkCySQVuGAeniBL4e6THzMOXfbK3dynV0DhbFNhEDDlk+b+TkAglsgX/8wy1wDQbtv0PCkRs2ukCn0c5xV71fEKRTg72QKFKtYCLIYmPYls+KnvqWgg7nkz/MG6Rfq0RHv3NgeMj0NllIQx2jfNOaA/4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.221.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wr1-f41.google.com with SMTP id ffacd0b85a97d-3f99ac9acc4so2933693f8f.3 for ; Sat, 27 Sep 2025 21:49:22 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1759034961; x=1759639761; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=DyUaaqdWAgLg9ININm7xedY+UnymRaRfwlVA8p6wolQ=; b=PupmkHR2N+Iuej99WUtanF/H7Ql0OeW4mQzLEiuf+1Z+qgnsbIKRQ7aL4uTE2ERyU6 fwAn4+thq7aHj5668/vaLk3RXOUQNAnDiRikRZE7br53AmYQd0D+FwdVAR7uIM/jYJI3 Xevg97Hr5UruLkwXaN83wAIoEiFM61HxNBB2yGTqoFYGZeaAX7ZJBXKfUZOtvpd8B13J cFyDrT67eFeJveR1qI7UzxU5BWrda9LBrQa3+rkwnmcY9U3DGGnfqvZHmEyi71sfXizZ UUsFezMWH7eIR/wGAafWwSw5OPJqME0iu5ZoOak3Dj2fHWnUxpW6f1xexWYFcCzQxtVG ZUgA== X-Forwarded-Encrypted: i=1; AJvYcCUAlQwoJ+vbyd+H5171Wq+O0Ll2bVtdCFgm6m3EMD9ION0Umx5BbcKgAzvKGdmaFQjcuI1z/GEsbHSzZz4=@vger.kernel.org X-Gm-Message-State: AOJu0Yxqn+ieR15Y3bRHEUp6EIOn4/aCKZwk+J2kqnFcUnaxkyRxnWtY rCOqQIkmXvdLsaMsLAikn+EbfRyRTLB96iBL0mynFbwKunZjpijw15t4 X-Gm-Gg: ASbGncsCe+DVq5qLU5U2SJAL2xmsYLKAriNB10RX+/70jqWpE3yD2/v+VSbqDG4wgO9 oqEkmgUiWl107/fU4sGbKbl9Pj5MVCs62Q/jM6DDfQ7lxXpRLqld7JvcOa4pOfftxme99r5dlWG UHPundBPLl6P0kOuX3ApaaSlQkVsQ9dmkPKMLYyipIzCww3PGrMg1QC4DmuscI4/sfmSE9B8qyb /YlW8/J07FKLROXMP3ZzvSMlx4WFiZl07auTsBQmmchOVJR5Pt4v+0gyrPdEK6AmqhgHOPPfDyC 5lhbtuGqvto1tllIQa3lHEglAuu9TEZFjtbJKVNuvv+sYPDo+lMkwgZ/zIzyywgzDvoZM2x1xPq UNVh5wQs910J/DuTTyLkaHODIZDZBxYOYSg== X-Google-Smtp-Source: AGHT+IFtXLQOdcvQ7Xjrg3v0c2+UOl4vx5bR+h7AWQ6ssWZLLcWyTpq2xRAkUoQVnuyBrbH3ylk2aQ== X-Received: by 2002:a05:6000:2dc9:b0:3ec:ce37:3a6a with SMTP id ffacd0b85a97d-40e4458ce65mr11243196f8f.22.1759034960758; Sat, 27 Sep 2025 21:49:20 -0700 (PDT) Received: from EBJ9932692.tcent.cn ([2a09:0:1:2::302c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-40fb8811946sm13119628f8f.18.2025.09.27.21.49.10 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 27 Sep 2025 21:49:20 -0700 (PDT) From: Lance Yang To: akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, baohua@kernel.org, ryan.roberts@arm.com, dev.jain@arm.com, npache@redhat.com, riel@surriel.com, Liam.Howlett@oracle.com, vbabka@suse.cz, harry.yoo@oracle.com, jannh@google.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, usamaarif642@gmail.com, yuzhao@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ioworker0@gmail.com, stable@vger.kernel.org, Lance Yang Subject: [PATCH 1/1] mm/rmap: fix soft-dirty bit loss when remapping zero-filled mTHP subpage to shared zeropage Date: Sun, 28 Sep 2025 12:48:55 +0800 Message-ID: <20250928044855.76359-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Lance Yang When splitting an mTHP and replacing a zero-filled subpage with the shared zeropage, try_to_map_unused_to_zeropage() currently drops the soft-dirty bit. For userspace tools like CRIU, which rely on the soft-dirty mechanism for incremental snapshots, losing this bit means modified pages are missed, leading to inconsistent memory state after restore. Preserve the soft-dirty bit from the old PTE when creating the zeropage mapping to ensure modified pages are correctly tracked. Cc: Fixes: b1f202060afe ("mm: remap unused subpages to shared zeropage when splitting isolated thp") Signed-off-by: Lance Yang --- mm/migrate.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/migrate.c b/mm/migrate.c index ce83c2c3c287..bf364ba07a3f 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -322,6 +322,10 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, newpte = pte_mkspecial(pfn_pte(my_zero_pfn(pvmw->address), pvmw->vma->vm_page_prot)); + + if (pte_swp_soft_dirty(ptep_get(pvmw->pte))) + newpte = pte_mksoft_dirty(newpte); + set_pte_at(pvmw->vma->vm_mm, pvmw->address, pvmw->pte, newpte); dec_mm_counter(pvmw->vma->vm_mm, mm_counter(folio)); -- 2.49.0