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 37D7926ED40; Thu, 5 Mar 2026 05:39:27 +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=1772689167; cv=none; b=NOtNdU+abpeHuJysYSOJT9Qla5rbkmgUEMF2yQ/AkUIxKv6OUJL5RbvZKiTqJfT6rbTyf02WuW++PYjd5IqywekWU6FW6x++thGWcO7+paezXdkYD7uYSrK9ivPzZdvc5VeQPAlbuAao3U5fhl8htp5HoaZSinsnN3cxUEKkr/0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772689167; c=relaxed/simple; bh=5/X4eJG+KDqPgy0/cAl7n9bW0ZJjnLYl+8/7GajTl5o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=u+fZtQxYm8PivOZmiw4bU+oJJF65lDjOqdLEMAnEbU2npzr5XgM3EvUH1au7LqyysIK8lxWjvSuaMWGNdcXzUtCPKk0/eoiB+K4N2TRJBelzQwWWvc9Uyeg5pHpM/gbLd4UcgDejKAIgQ47vnCg1kf7XdN1KWydMEthMS9tHVyI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FYMSt3OK; 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="FYMSt3OK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02D48C2BCAF; Thu, 5 Mar 2026 05:39:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772689167; bh=5/X4eJG+KDqPgy0/cAl7n9bW0ZJjnLYl+8/7GajTl5o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FYMSt3OKRm2Q/erGqug9bf8DAHBkt2DL6zzKTcvHoWaBbfOocX3WX97d8kmNAHvuj lLoWNXUswuN59Y1esfNNeV4yrTPWR1gJWAhzsiogLPiRb7cYgJsa0a8cxarnHHbc5Z O9Jvv+IAcfAMGv2vrfiFhaKYyRKQy2vqPJgPA5R/dq7wzn8kivgL0Nvgm169rAY1B4 QR7wm4t9G62/zAEZ3Jvw0qskqM1DB07SaGEn7LLEYo2Oee3Rl+gYby2fH97hbsrCuZ M9hABnGurlCM4qF5vldHcdy8si3mBsJsDRSoUm1XA31uivM8kD8JK7cYPPfF2HiTpq nbnb4BEAnGaOg== 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 2/5] mm/damon/core: support addr_unit on damon_find_biggest_system_ram() Date: Wed, 4 Mar 2026 21:39:14 -0800 Message-ID: <20260305053918.83786-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260305053918.83786-1-sj@kernel.org> References: <20260305053918.83786-1-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_find_biggest_system_ram() sets an 'unsigned long' variable with 'resource_size_t' value. This is fundamentally wrong. On environments such as ARM 32 bit machines having LPAE (Large Physical Address Extensions), which DAMON supports, the size of 'unsigned long' may be smaller than that of 'resource_size_t'. It is safe, though, since we restrict the walk to be done only up to ULONG_MAX. DAMON supports the address size gap using 'addr_unit'. We didn't add the support to the function, just to make the initial support change small. Now the support is reasonably settled. This kind of gap is only making the code inconsistent and easy to be confused. Add the support of 'addr_unit' to the function, by letting callers pass the 'addr_unit' and handling it in the function. All callers are passing 'addr_unit' 1, though, to keep the old behavior. Signed-off-by: SeongJae Park --- mm/damon/core.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index db388d05cac3f..38c7a919f9bb2 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -3052,31 +3052,44 @@ static int kdamond_fn(void *data) static int walk_system_ram(struct resource *res, void *arg) { - struct damon_addr_range *a = arg; + struct resource *a = arg; - if (a->end - a->start < resource_size(res)) { + if (resource_size(a) < resource_size(res)) { a->start = res->start; - a->end = res->end + 1; + a->end = res->end; } return 0; } +static unsigned long damon_res_to_core_addr(resource_size_t ra, + unsigned long addr_unit) +{ + /* + * Use div_u64() for avoiding linking errors related with __udivdi3, + * __aeabi_uldivmod, or similar problems. This should also improve the + * performance optimization (read div_u64() comment for the detail). + */ + if (sizeof(ra) == 8 && sizeof(addr_unit) == 4) + return div_u64(ra, addr_unit); + return ra / addr_unit; +} + /* * Find biggest 'System RAM' resource and store its start and end address in * @start and @end, respectively. If no System RAM is found, returns false. */ static bool damon_find_biggest_system_ram(unsigned long *start, - unsigned long *end) + unsigned long *end, unsigned long addr_unit) { - struct damon_addr_range arg = {}; + struct resource res = {}; - walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram); - if (arg.end <= arg.start) + walk_system_ram_res(0, -1, &res, walk_system_ram); + if (res.end < res.start) return false; - *start = arg.start; - *end = arg.end; + *start = damon_res_to_core_addr(res.start, addr_unit); + *end = damon_res_to_core_addr(res.end + 1, addr_unit); return true; } @@ -3106,7 +3119,7 @@ int damon_set_region_biggest_system_ram_default(struct damon_target *t, return -EINVAL; if (!*start && !*end && - !damon_find_biggest_system_ram(start, end)) + !damon_find_biggest_system_ram(start, end, 1)) return -EINVAL; addr_range.start = *start; -- 2.47.3