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 633953806C1; Thu, 21 May 2026 14:34:38 +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=1779374079; cv=none; b=gKtUM5OyOBcYK5oOFiG5BLEYLwnTQDh07WixiYym/0clq1W9XT3PwFZjgpr949VTyOytJFCYlkn2D9RLTnIYB/W4mbePASiV5UbYLHHAp7BklOGBR9zFf+LPy5rUjojQtAZTL1cebwp/RTp8xpdQt02bdc/gfmpIAZi0w5JKNfw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779374079; c=relaxed/simple; bh=SeQSeIT9kw4GiQ+HZa+CgcRvg0CvL1bbL4gPUN4MWDE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oWf8Yv9e3Q20taKN679ONcM4BiRN/7i+h+sn8+P4HzB9Yq121azkQpeuilm6b3RE4PB/8T6sZLZQdLLkPlazKRxCGS8BnMRIYsH4KzO9D0S73UcHrnYeQMj0uHVQoACGJ89+UNw/JD9YBI89rIuWOjm36VJ4spShIpteCw23TNA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bWEuYdaN; 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="bWEuYdaN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 07E491F00A3D; Thu, 21 May 2026 14:34:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779374078; bh=iMM8ZRfSsARmGo6eD+hRIbIxGHEMj2jHM5nMAylgAOE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bWEuYdaNmVFDjKsvRuqq0YJHRvCUaAx2GvJr9y3wf/72QFXCBCP5rUH7TqGW7iQJE bBZZpk650IhubHqIwaD3RR3WZ/xBWzD+e5BtzDBK8V5caF6krimBN09VdUGqiphQ9i G+Wwgm6Ghl3smylvGOwZDVG1E49zp9cH+irT9akiBGo/ubPnqxpn44F4JENymzjUf+ y06/U4llsZhlI3lzFZ9wFOUyu29lPX6yKhem0HuViWrgSrqFYaNMoM+KhkE+S0nsAT tqQhxF3Zefm12Ssc4iXZRH9BxQKKNmIREsYxTkATQT3YIHarbKSNBWh0z71oQlf7T7 JOTLdLi+PrT4A== From: SeongJae Park To: Cc: SeongJae Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1.2 02/14] mm/damon/core: do not use region out of a loop in damon_set_regions() Date: Thu, 21 May 2026 07:34:12 -0700 Message-ID: <20260521143428.83157-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260521143428.83157-1-sj@kernel.org> References: <20260521143428.83157-1-sj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit damon_set_regions() assumes the DAMON region iterator is referencing the last region after the region iteration loop is completed. The code is indeed implemented in the way, but that is not a documented safe behavior. Hence it is unreliable and difficult to read. Cleanup the code to avoid the case. No behavioral change is intended. Signed-off-by: SeongJae Park --- mm/damon/core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 40946a7f6f549..e8cf3632115e5 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -374,6 +374,7 @@ int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges, for (i = 0; i < nr_ranges; i++) { struct damon_region *first = NULL, *last, *newr; struct damon_addr_range *range; + bool insert_before_r = false; range = &ranges[i]; /* Get the first/last regions intersecting with the range */ @@ -383,8 +384,10 @@ int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges, first = r; last = r; } - if (r->ar.start >= range->end) + if (r->ar.start >= range->end) { + insert_before_r = true; break; + } } if (!first) { /* no region intersects with this range */ @@ -394,7 +397,11 @@ int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges, ALIGN(range->end, min_region_sz)); if (!newr) return -ENOMEM; - damon_insert_region(newr, damon_prev_region(r), r, t); + if (insert_before_r) + damon_insert_region(newr, damon_prev_region(r), + r, t); + else + damon_add_region(newr, t); } else { /* resize intersecting regions to fit in this range */ first->ar.start = ALIGN_DOWN(range->start, -- 2.47.3