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=1794591131; b=sS00FgHOkOO2siQpKYpMnCi9Yr2ef/QIP06zsHEUGBWnoxo1jfNlwqTCg3OipdCxd3xy agY3RV9HYG3MiugYeMR9SVapbxj1CNBgGOQkiCpcLDBgdb0Rw5BowEDP4mWfZ04cRBOoP vpltlXOV1+S1gOTNNnMxx/vdr0i2IqJTuZE8LvSkVa3CB4YZa4FI3agu7MIf7SoHUtpw3 YV4uL9NFXc6yomBS8HdqEInmbJ+OljCHGwvPLmFtBhmp0GfM9kMs9THDOjD7HkwKyoY88 kZ1XOueM4XWZ9AMtuhbi5FscQd9snHOcgoEI98wb9bE+dSpr4n/aeCzg6JVCXK5lE7w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794591131; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=QkAF+CNhbg2ifBMpe8iwhjeSYHPVwHlY+IDECRqq/Kk=; b=DaD810fg50xCA6QRtSnai+w9/lNKOMwLP54yb0ymeGUTa210cWHLkBYuu+9XhiXuq3Qw 42LH3mhNueoDzczoErAi6HWzA1HqP3Iv5hjnNl2bqLJmyooRVLvqpOtNlWxbiUpuJKsxa yUrORDCMdfk3PlYr07OGBrFDAqAWWMxW31a8GuGys3nEKLDSEChmdfv4IVAl8gTUf0hKY Nx2Z/9dYDqPjsd5a6+rZARx4G5PN0hLyKYh3ajT36s3hleWRuP4dCwh0K/tsN0XBLvb+g aa1nCgcGTIViVf/fAZ7fugE7NhlYqACUf4LypuS9kQVCncBHGmARI/9BctKf620m45Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ZBFB3TwW; 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 C3688606A88C; Fri, 13 Nov 2026 17:32:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ZBFB3TwW Received: by smtp.kernel.org (Postfix) with ESMTPSA id 764E71F000C4; Fri, 13 Nov 2026 17:32:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794591131; bh=QkAF+CNhbg2ifBMpe8iwhjeSYHPVwHlY+IDECRqq/Kk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ZBFB3TwWa0Wza1Tt3Cc0czvbNhS7zXHXzjpVCRQEg8foYlIUt6UJBeB5/iSbnHjua jpgDakCdBCUdQshEeTzxNoidKKwXJwn+9byxvL9pyoYx292y1E0xOnfe42u2QR60CZ h3eEiQ9FJ4IQQSK7PimdYH6FdPekkKLA4qF+a2RE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Samarth Narang , Andrew Morton , Lance Yang , "David Hildenbrand (Arm)" , Xu Xin , Chengming Zhou , Peter Xu , Kiryl Shutsemau , Mike Rapoport , Sasha Levin Subject: [PATCH 6.12 278/670] mm/ksm: keep soft-dirty when merging a page Date: Fri, 13 Nov 2026 10:47:22 -0500 Message-ID: <20261113153821.305848593@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153811.177190860@linuxfoundation.org> References: <20261113153811.177190860@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ 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: 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 15f558f69093a..aba53b4a3b978 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1407,6 +1407,10 @@ 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_get(ptep))); /* * No need to notify as we are replacing a read only page with another -- 2.53.0