From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 04D1ECAC5B5 for ; Mon, 29 Sep 2025 10:15:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 471FB8E0005; Mon, 29 Sep 2025 06:15:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 449CF8E0002; Mon, 29 Sep 2025 06:15:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 386258E0005; Mon, 29 Sep 2025 06:15:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 26FC28E0002 for ; Mon, 29 Sep 2025 06:15:48 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id C141113A508 for ; Mon, 29 Sep 2025 10:15:47 +0000 (UTC) X-FDA: 83941881534.19.0B4D2C2 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) by imf30.hostedemail.com (Postfix) with ESMTP id 8C2EE8000D for ; Mon, 29 Sep 2025 10:15:45 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=gzO39fAC; spf=pass (imf30.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.170 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1759140945; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=0lDTfGg/6Uyqwfi6NmuvIilfdfFny0fXjAuu0Bjee84=; b=5sVjrOPn7BsALXciWZ5mq6F3+zii46dM/m4IwYIQK03KGl13vdu5HmnvVLvUVTOJJk82+j 4XzootUPXYHJaFpROgTvkGyfWh6QBRscCtZCPr+4YBE2fv9ViKDZiH+VnfTj3aWy1uv/D9 Ruz2s5kY5z3GOjCn/eoJX7wnrkSJWzE= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1759140945; a=rsa-sha256; cv=none; b=hCFs9Ti+Vmb1kYK9B/2HDHaRenmn06mJKLvHfyZy3frhc0LOBCWrK3QWf7DlXB7Rb716gs RF5/IcQAVOXqgQL7iC3b+r9DeLiQIF8R7ZbuEov+AKbaHFdXSd241ppC4yisuWZkHZSwA1 FLq6nj/2hS92vijfO1a6ORfqhWVTxeg= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=gzO39fAC; spf=pass (imf30.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.170 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1759140943; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=0lDTfGg/6Uyqwfi6NmuvIilfdfFny0fXjAuu0Bjee84=; b=gzO39fACECb42zPXJwdyj6Jv27mioHJsXOtNOgcfJ+jWFO9VImd3+gUNkHtBP/obtV3B7B pFJMjkkPJqkUu67chDrlvcIkKpsNMrW9Bn08O92QVgLhNIqIFhRQ4VYEvvxjJgrjLaQWri YMHMpUqryT0WsiiYzr+1JRdaCwrF8G8= Date: Mon, 29 Sep 2025 18:15:29 +0800 MIME-Version: 1.0 Subject: Re: [PATCH 1/1] mm/rmap: fix soft-dirty bit loss when remapping zero-filled mTHP subpage to shared zeropage Content-Language: en-US To: Dev Jain Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, baohua@kernel.org, ryan.roberts@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, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, david@redhat.com References: <20250928044855.76359-1-lance.yang@linux.dev> <2065263d-a2c0-437e-a096-695c6d17f97a@arm.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <2065263d-a2c0-437e-a096-695c6d17f97a@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 8C2EE8000D X-Stat-Signature: iz5xr9acfdx7ar9xdttgdbktsb7rrtpy X-Rspam-User: X-HE-Tag: 1759140945-385866 X-HE-Meta: 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 m+dQAPIL Eclsid5Xu8wDQ+InawhdDVj8uzKLwcwL9ME5FIz6U5WcIgD0ZNQRKlFZ6HMwxQ1DCbZXVLsMJ6+xUpvEPzQyYqJ8vepqllcXCdCTzd9Ihn44ubab4PH3BY/NfSUYLWihKkr5MoE/tlnvxnWnfpZ6qr35DJiYRNxJgqiLaaUlhzLLRplGbFqaMNXyec4AIUkCWXZ1nZ5zJ8JD5cssCgEJNrpdVrkSM+Bh6GOu7PYqDQE2/376df+nj1/FjyMuezmBDibUDaJasO3Hqp4VUX4cPadWCBtyi6JvfYlJLP0qa14Vj8c12f6A/dh+E02ZbLkNT5brO0LPq+9vVTSs= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2025/9/29 12:44, Dev Jain wrote: > > On 28/09/25 10:18 am, Lance Yang wrote: >> 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)); > > I think this should work. > > You can pass old_pte = ptep_get(pvmw->pte) to this function to avoid > calling ptep_get() > multiple times. Good catch! Will do in v2, thanks.