From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4E2033191BD; Sat, 21 Feb 2026 19:36:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771702596; cv=none; b=LT7+flGH1ZL7k4MInND79QATrz/8FZHJPDhur7v6KuK5phFEd7O+o+36OCpXgzhmN7M7hOZQIMD2bg/6Tdzik354C3dOKpH4xCNq7cs6IujL3O9QIFeIN27xJXPjASvaUq4nuxknfgbEYHhLc3NSo6oc2I0mQaNUMatVf4DZm3U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771702596; c=relaxed/simple; bh=RXFcEvIn0MWpVnnu1oJ3V6Kn3He/nSAmwf55lWBXXZE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NuGisXzq4Iija4hLBsz4FktleoSBBEG7l5Y6IKf7kPN/QV9j70/ajzdVrj7VlO89cDm6nBQva+AJg9kOT1H0TAbm22H6Moue4Z/28EHlrYpXHBVZRAWELBkdoK0djD9oIQJ9lUAmxc84MzOPOSJXwzY92mycLY/F1tp8kdPUPoc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZLgrWyhw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZLgrWyhw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E11EC19424; Sat, 21 Feb 2026 19:36:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771702596; bh=RXFcEvIn0MWpVnnu1oJ3V6Kn3He/nSAmwf55lWBXXZE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZLgrWyhwax0cT7nz0xs/EG9v4tu/MXv7OA36zpiRe2CNexw3DJQnjeNnnVtyo4Vxm 4Rkn7BFF5uU6H1th8z0cFPpFFImYeswzF2ASAGdvmkiJEG7rbMYYdogAiu1IWefaXX UvHXjfodd4SRfEWISn9njL7ykKKALl86yVFpDR/kXFZj+ylG7hSQLAo2NVyrxJ7Ib2 sxPu0GkvnKLwbdzMY01yG6zEnhaMBa2HOWq4L75Nrj7kLEfZ/UuLxbnCaPIykfSiCo L2i0Q7TedqgX98EGs6WaO1aGc+xO1zGtnUkM3ovSuNg7OG7SzZmoHpjuARgz95HecE 89GY/aErOPc/g== 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 05/10] mm/damon/core: add damon_merge_two_regions() debug_sanity check Date: Sat, 21 Feb 2026 11:36:22 -0800 Message-ID: <20260221193629.19332-6-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260221193629.19332-1-sj@kernel.org> References: <20260221193629.19332-1-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 A data corruption could cause damon_merge_two_regions() creating zero length DAMON regions. Add a sanity check for that under CONFIG_DAMON_DEBUG_SANITY. Signed-off-by: SeongJae Park --- mm/damon/core.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index ede76e0789be3..291a847a8c9bb 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2507,6 +2507,25 @@ static void kdamond_apply_schemes(struct damon_ctx *c) mutex_unlock(&c->walk_control_lock); } +#ifdef CONFIG_DAMON_DEBUG_SANITY +static void damon_verify_merge_two_regions( + struct damon_region *l, struct damon_region *r) +{ + if (l->ar.start < l->ar.end) + return; + + pr_err("damn_merge_two_regions() created incorrect left region\n"); + pr_err("l: %lu-%lu, r: %lu-%lu\n", + l->ar.start, l->ar.end, r->ar.start, r->ar.end); + WARN_ONCE(); +} +#else +static void damon_verify_merge_two_regions( + struct damon_region *l, struct damon_region *r) +{ +} +#endif + /* * Merge two adjacent regions into one region */ @@ -2520,6 +2539,9 @@ static void damon_merge_two_regions(struct damon_target *t, l->nr_accesses_bp = l->nr_accesses * 10000; l->age = (l->age * sz_l + r->age * sz_r) / (sz_l + sz_r); l->ar.end = r->ar.end; + + damon_verify_merge_two_regions(l, r); + damon_destroy_region(r, t); } -- 2.47.3