From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794419139; b=4IFvzVSoq55T0bxYTuKeeZv+GEUaHm/WJ36szh3mNiBwgL00c2fCEu854CO9J2Im8GSH s3/6AIOMoxiR7DzkKdtisCp0Z8yvGsWa72EeU2tbdFRbIHcvhcmG3sPe+sHjvvMRmx3a6 srlVBloXzmWr7G0vU6MJ+158C5FaeCxLwmDvFcognPuGDiCsperDGRItgsSzsBulPRIiN SlUJpsgffBhWOmD3dlmSz3PA3XKfy5OQOSivhHc7X9NW9h0EWjyV0ZjavDKHLPy3VRnEM /dFJHhTVF+axgU77dFfyl/4A1u2GlatnprGfsNFA/fHyY0/jAxwm1eLYVAakExtPpNQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794419139; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=cVZMS7plCFhcLSpzUPKcqs16DyXXNTzX3X1i67/v02I=; b=ZMYmVdZpFUw3RgFcnUMrXtpJZuTexBX7FP2HwCxG+U66mt6F6dIJuIvZxu1Ldyx9wYge m657XM/aMRjRmBE2lYZMm6VDcXZwPxq6Cpi3fNcRaDP/TdL1FRY2etRsaO8fDm1ZQEXrB HiOXFkM7+US/0yQtHxm3z4Ubm8BLPkxoB7LjFbXn535flqJIVxGkAyCSqM9HCSooAqXbw /pEjS8u9Q5TCXJu49iaz4t244kFHcsg03eot8YB+GMKuItx+j8ovF2mC4SLUpeSEhLMyG O91MJYWwI2h2zsV5ElfwU1tNYtg3SAaf+DQVWgVAwppIyzZuClA9Mz3hWhVlYhLhcPA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PmmvhFGJ; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5BCC4606A89E for ; Wed, 11 Nov 2026 17:45:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PmmvhFGJ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 260271F00A0B; Wed, 11 Nov 2026 17:45:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794419139; bh=cVZMS7plCFhcLSpzUPKcqs16DyXXNTzX3X1i67/v02I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PmmvhFGJxzskSobyrH2XfiI2XvB0Ze4dQuaGF9DgJMuK3IM5KzUMEleWeefyVyrBx XPKfmYuwP0RTiMAx/RnH/WBikiarqTsYVRNu02iBHKyC2xKaR3BTUhaXlrvgy151qK vl1m+gqJTM/Szl+SGAgxW+o/676Eekp9hvmrFaONgkcNBsEw/3wIaV69sow3CKnewN qbdDKNYDDhXeqMhXRYZ+vX6ngOnFPPbfcLDtgYJwg/U+FrG1mJ3ED/275NVkrqi1D1 FRN9TQd5dD+8FGzbdIJj+n+KmXNClcSerl/rBeMAYybgFEufn6fK6GL8ODFrQ4RKZb kdlTMUan+Fbag== From: Sasha Levin To: stable@vger.kernel.org Cc: Samarth Narang , Andrew Morton , Lance Yang , "David Hildenbrand (Arm)" , Xu Xin , Chengming Zhou , Peter Xu , Kiryl Shutsemau , Mike Rapoport , Sasha Levin Subject: [PATCH 6.1.y] mm/ksm: keep soft-dirty when merging a page Date: Wed, 11 Nov 2026 12:45:37 -0500 Message-ID: <20261111174518.3654526-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109201702-failed-6.1-2efc6332f18b@kernel.org> References: <20261109201702-failed-6.1-2efc6332f18b@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Samarth Narang [ Upstream commit 2efc6332f18bfd848f74f3d5ba45b31450601faa ] replace_page() maps the KSM page with a PTE built from scratch, so the soft-dirty bit of the PTE it replaces is lost. A page written since "clear_refs 4" then no longer shows as soft-dirty once it is merged, and a soft-dirty based dumper treats it as unchanged. Copy the soft-dirty bit from the original PTE to the new PTE. Link: https://lore.kernel.org/20261021182157.1873726-1-samarth.colleges@gmail.com Fixes: 0f8975ec4db2 ("mm: soft-dirty bits for user memory changes tracking") Signed-off-by: Samarth Narang Signed-off-by: Andrew Morton Reviewed-by: Lance Yang Acked-by: David Hildenbrand (Arm) Assisted-by: LLM Cc: Xu Xin Cc: Chengming Zhou Cc: Peter Xu Cc: Kiryl Shutsemau Cc: Mike Rapoport Cc: [ sashal: Adjusted context to retain pte_pfn(*ptep) instead of pte_pfn(ptep_get(ptep)). ] Signed-off-by: Sasha Levin --- mm/ksm.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/ksm.c b/mm/ksm.c index 99eb19860fd59..c976e41f853b0 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1178,6 +1178,10 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, dec_mm_counter(mm, MM_ANONPAGES); } + /* Preserve soft-dirty when replacing the page. */ + if (pte_soft_dirty(orig_pte)) + newpte = pte_mksoft_dirty(newpte); + flush_cache_page(vma, addr, pte_pfn(*ptep)); /* * No need to notify as we are replacing a read only page with another -- 2.53.0