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=1794419596; b=33HYiFoCkyfGG5A7Wd2Xim0cKEAoqvAenyQuXOGHzPMw7BjDtyChTu24Lz9LVkFAeVRV wkcBGqD8HIw1AI7hSdhhdVfXl7CqT5h8dcB4vXX0O6pHfNxwCC0uRBmcvabuvfD14oo97 ze9jM080CZpWrOJTCzmBXKMaqXd7SU9SYupKMwKynXE96Xpv5Jt+ZDk29e0Dvf0tmUGUu G+qxNvzOsY3DF6tGTPW6kGZcMS28oOQiTp4G91m3I/59h9DvaMeAS+VWx4OiQFbvXzkj9 zccb+yyVEhNGkP6ZR/DRenNbVHnrCfZbQ72Aw9/57kfKBJXcOF5vY2JAgkMRBNCjuSw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794419596; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=TH7qFfIZmZkGw4LcXefHnScdOxYHr4wYQr+eur5+Xk0=; b=4jk2+YroC9bYkxO6ttgV9Q7ydNJA4Y9YaQPf0shqgStC6jde5BPrECbkZ9VPPigm8u8E YTvh3T64zZPSxArgY8AuEwM6u/E0IQ1klgM0Xq+Ypcr7HAr2M9zTli55qslBrVSb46KRF 6l5xKZn1qyILf7SlOot61D+GCczsL/cEaGhkkdSqAQhFdsAa43p6sAFNXqJlpMd2j3u7C apGhljgGf7nCOCxpn+l34Pm3PSUveIrKwAEoQRr6vyBlm+GJlhIUPFiKJS6f83q+jypie kb433dPwCxkqj0wF7VxaPkO7+IJAfnW8aYHoQhc3ELOE/EDWRFumST5iTBUr1NtRRDg== 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=f4oR6uQg; 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 6C34E606A31C for ; Wed, 11 Nov 2026 17:53:16 +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=f4oR6uQg Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3884B1F00A05; Wed, 11 Nov 2026 17:53:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794419596; bh=TH7qFfIZmZkGw4LcXefHnScdOxYHr4wYQr+eur5+Xk0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=f4oR6uQgp9iR1bpX8tq+VZP+cgXKurREZSgZfaqyuecYPzx8j0SK2pUFTfs8O0meB yzLRaa/iiTgMWy03TxKiVuXcqRFPAHAGfC2bBWZ++BVyuovze8U8DxzdKtxbDrt6Tp XEGUcrKAGer+ITcGIqy8Y0p8MLNG+pX7Nt9+wtoB1wuAGI/5HC3k9fiueDVGQisDJa 5rmDNt1yweB41qZgGi1o8cSJC1z/6UxUuGC9EIMYoZKMmgSI+Cw6EWoH+f7WxMz63a Q/Eo6UGQEGXYPlqGbFPl1yX1B+s1Szs/hKyt6FXWjCIH4SDxpgnysIcUu4/1duFbwG jzCvpATUcwgeg== 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 5.10.y] mm/ksm: keep soft-dirty when merging a page Date: Wed, 11 Nov 2026 12:53:13 -0500 Message-ID: <20261111175257.3718842-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109202648-failed-5.10-2efc6332f18b@kernel.org> References: <20261109202648-failed-5.10-2efc6332f18b@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 for direct *ptep access instead of 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 466ca19997551..bc097bb03c1c2 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1170,6 +1170,10 @@ 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