From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f54.google.com (mail-wr1-f54.google.com [209.85.221.54]) (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 AD8AF221F34 for ; Sun, 28 Sep 2025 04:49:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.54 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759034964; cv=none; b=EO45I8EW9D6p0bgf0tDU+B/cuCpSsa+GaMdBlhMGs/PSQzVduI4f1SpqaddoCycVIF5RH15VTNstaNZ5A8U2rMEOGoet/++lFIEqjaGVA8sBxGLgPkAwXV4Kh7tLqKArE3jauOrlvIORFpIWy5k77Jb3Rj1odGqMmNHO6RA+o5Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759034964; c=relaxed/simple; bh=3JXHdTFd0Do4NsJQmtnD90PGDnc76HJueRPgFM3FauY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=rbUxKhxGRlaiIynvDLH0V5fdixUleThGcg/saOeFnW95qup3uWE2DzSXNaLaPWzEjCXctKRROSEL1QfuUSKcwNIXt/WyYPQwKaBcN+LiNXFbuJVfvZ/+cuMMo0L2XV68S9167sNzcd7lo2cVhnPZW8f5Q1P6IFMyX3RjJkmqJjA= 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=209.85.221.54 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-f54.google.com with SMTP id ffacd0b85a97d-3f42b54d1b9so3478613f8f.0 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=lPqeuiDb9VdmJw1Pwwfxkgwx0POZH9+KJ7YbqjfG9e5EYFILC5bofvj63HtVqcIjTl fp1Y0rM9MhrdGz/r6jsOb+MhnNqXt4dBJcsLhJX0lC3mcWh/llq58yMVZKnOZTRn6X05 ThvsmLLXIScOjZcZS3u1upM8E+TlCU2ib6a0TXpOD9H5iU0SQ16J4TcYRbek7SbFTyMe RolxA9ePkm2ZymotEIevFEujqGpeTvhchAuT7IEfkkrKczHMwJsfo84i3p6RlBDtrRhZ WON7Tr/BjxqvpHVfahXQwss/Kl+LfF6TUAndUz1kJc9p/dh8PbBYsBu/jFbBFw54C8Kl QO3A== X-Forwarded-Encrypted: i=1; AJvYcCW96lvZxjFepZzygMKD3RaC1tIcOnL7BvgdKr50zXYw6lBvOZYMTQeVQcZVwNuTDC3nViFIdBo=@vger.kernel.org X-Gm-Message-State: AOJu0YxchvTfgwdrZPrtA/V4wT9paa1fFj116RMdT7h3ClwVb+suv5Ss LCdNxP/TgOlyv8BWC7B+Xeqv7on2yKHEmsIrduNrgDD7eUfNj4/OQkFa X-Gm-Gg: ASbGncuoaSNz0rXKdhfOgnVOF9r0lIDFDeb0hwvN9sKqyLH0aouL2LCL/0af+Za7nBF G0VEVoskRZx2e76QaMWO0/aVlwdHSvJ7KaScoSG6AjaVWK5ffpgmAsOTUVDgmOdi2Oe/JPuCept FF7uk/JSzj/Ehjf9yvvP8LROpPaJpLiUbmlqg0DJjADTdpg6b47V8GWskSX1pCXxvLqcoFTW8sw yOWPkbU4LgWUozk+gM4XmGjjKjH9qtuiBLFEBuErS6BhQ1pCAZQTcqwGDKsbB/visxd4huxhPZV USpkr5V7lpMMQBITeHQSXdaESrIB6BiAwXi+Aug3Ix0amZBss4SnI46aiEUDrM+ucCe0Lk08E27 fBxwnQ1/xJ3atFql/l/7HxuBDvKXAX4QdmA== 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: stable@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