From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2FA664854FC; Mon, 31 Aug 2026 14:03:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788184985; cv=none; b=igOj5B6pZQvJHicIhIHPhkDUu4vim/nykhhgSjMv0axQPcfCtYAZBrHLnCdRr+zDLrAeCjpj9ImJWWpD5x9rV5pw7A8HgG2SflgOFvO7am5CNSog+c2w5nzrjnMJA0IAnVKkh5F70/tyG6ypwc1D2fCUtF2Q+MYA5Hg3ZCQaFP0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788184985; c=relaxed/simple; bh=5AGJ58CxaHUHnA7OwFTsM+2rMQoeaY6UpbD7qoJcoXk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BvWxT8grh2jMa/ZCbF+LxUsiiROuQkh9aPbX4/CXhXevHSU5C+pggX6MDZHqiADN/d9AgMJ+1uVrOm7sFdqZXAwqVF3AAKQ1j2hYZUyic5dGkbbK7GL6Dkfwf2K8OzEGQw+DLgSL3t/gSHU33kp37WEEt3QbKpBs04AD01qAwCQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TGzATSIN; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TGzATSIN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5E201F00ACF; Mon, 31 Aug 2026 14:03:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788184984; bh=nSTjwnDV8A+NiGPVQu+FC6bukzN4Edj/bjp5VqLzRxU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TGzATSINz42tKbEmPPTcS4J9tASvuhG6q2ioTy7mYUo2FOsQA+bY3ccQjSzWis/QN QMqkOCwDM5mJRH1zLaR421tWxE1piSSa1KRtVKWamXiwOzmoitvQnfWHvW+dl/DYA9 75rR7U7JuWkaK55dlUNdvknDGqIDpIUPTvVVnZJllJ5v0FI6IDWa8xWeQn9kDr7Q5v otERl2mpbErQaw/3QwaR2o64E5Z0ZzJ5KYuqTbM+lgGUQ9fqY7XgFZcF3/pDQjrCaF TlVkTEHyEuZ2hhpTttLuv9uK2OR5eWtZVA5uk8LTaGf2kOnSGkilVygLGQ+z5MjqZg x1hdN0POOUXcQ== From: SJ Park To: Cc: SJ Park , stable@vger.kernel.org, Andrew Morton , Yueyang Pan , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1.2 4/8] mm/damon/vaddr: respect folio end for DAMOS_STAT Date: Mon, 31 Aug 2026 07:02:43 -0700 Message-ID: <20260831140254.72004-5-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260831140254.72004-1-sj@kernel.org> References: <20260831140254.72004-1-sj@kernel.org> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit For applying DAMOS_STAT action to a region, DAMON virtual address space operation set (vaddr) calls walk_page_range[_vma]() for the region. The pmd walk entry function, namely damon_va_stat_pmd_entry(), applies DAMOS filters to folios of addresses of the region in the pmd. It starts from the walking address and advances the address by the size of the folio of the address until it goes out of the pmd or the region. Let's suppose it is for the first pmd of the region, and the region start address is in the middle of a large folio. Also, the next folios are small. Then, some of the next folios could be skipped. Fix the issue by advancing the address to exactly the start address of the next folio. The user impact is that the DAMOS_STAT-based page level monitoring results become inaccurate. Since the page level monitoring is supposed to provide relatively high precision, this is definitely a problem. It is arguably not critical since it is only monitoring quality degradation. The issue was discovered [1] by Sashiko. [1] https://lore.kernel.org/20260514015053.149396-1-sj@kernel.org Fixes: 63f39737d1e3 ("mm/damon/vaddr: support stat-purpose DAMOS filters") Cc: # 6.18.x Signed-off-by: SJ Park --- mm/damon/vaddr.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index 0648400b2d65b..4b0b5edf67952 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -831,6 +831,8 @@ static int damos_va_stat_pmd_entry(pmd_t *pmd, unsigned long addr, return 0; for (; addr < next; pte += nr, addr += nr * PAGE_SIZE) { + unsigned long page_idx; + nr = 1; ptent = ptep_get(pte); @@ -844,7 +846,8 @@ static int damos_va_stat_pmd_entry(pmd_t *pmd, unsigned long addr, if (!damos_va_filter_out(s, folio, vma, addr, pte, NULL)) *sz_filter_passed += folio_size(folio); - nr = folio_nr_pages(folio); + page_idx = folio_page_idx(folio, pte_page(ptent)); + nr = folio_nr_pages(folio) - page_idx; s->last_applied = folio; } pte_unmap_unlock(start_pte, ptl); -- 2.47.3