From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 519E33A3807 for ; Tue, 10 Mar 2026 12:41:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773146473; cv=none; b=NV7E/1B7l5GyAYT9w0Rl+9wWqX6bap0rt0kMqM+UcPJgJxC+6zX2k238HR1uWT1FeCZ2EdypzWYR/n8oLNX3Tdxrj54l65/vSHQhDLm5Yd3O/Gn1tVflyS5AVXHcoOy2dEajMr8KgI/A3buxHpirXHvWPBzuffUcgmYLNhwqIPE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773146473; c=relaxed/simple; bh=8E8reBvWD2CdU0+4Em51TQTQgyIsh+EJbeOc2ahYaI8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kxtZuTSSVIKHfR8/b+9LBtHgbVlrDwDYz1TTyFXx3EVZeC+whn75jhmC5+HSvIwZY3vpgHD2J3OOckGGJUHhVRBG+wn9TNJXvMMiW+HcpCF8yfOfnQ2/yy2s9lcqDIiljOM9iEszNmiaVwXcJZrrFjpwysjnd1ohVawsRgo7oyA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=JcoqtBh8; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="JcoqtBh8" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=23S97wgINlWLXAiGS5HNLUZSukSYxUCQHIDnN+UqDZY=; b=JcoqtBh8b1cfBMYuyuM0FhR0wI uqAjSAiHzKKwHs4YECVgh4dIA++lxMa9D0zb8oqcgpATWH2ifULpZMM/tJlaSWj9fbTw3qScjJlj3 lOAWQo7GC3mPmq4R2mGe68On4ggYcHLuxcksAFrB6RRKBxq7gM/Sl/EWrGEGR0BJsn2HR4EMHOjpl PuTMRmqYMN1ny06rVGELy1PAE2yeWJHG4nv2tsxE7GQaADLLfFzMNRejrnzo9WfJM5RKDifV4yDGb ckXbpUbeYmJX/UGWsQKGKDSOuPiBDucdf5Xb+OYO5NQXqIC0Ky6U4Za6uYvKpJHjj/lRfLdb6TsFy VpMR4+wQ==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vzwO3-00000007pkc-0XaG; Tue, 10 Mar 2026 12:40:35 +0000 Date: Tue, 10 Mar 2026 12:40:34 +0000 From: Matthew Wilcox To: Dev Jain Cc: "David Hildenbrand (Arm)" , "Lorenzo Stoakes (Oracle)" , akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, hughd@google.com, chrisl@kernel.org, kasong@tencent.com, weixugc@google.com, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, pfalcato@suse.de, baolin.wang@linux.alibaba.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, baohua@kernel.org, youngjun.park@lge.com, ziy@nvidia.com, kas@kernel.org, yuzhao@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com Subject: Re: [PATCH 1/9] mm/rmap: make nr_pages signed in try_to_unmap_one Message-ID: References: <20260310073013.4069309-1-dev.jain@arm.com> <20260310073013.4069309-2-dev.jain@arm.com> <21801fb7-0f42-4ad3-8b85-2ac6013b8aa5@lucifer.local> <31f93292-3de6-475c-b7fe-82ef41a3a7de@kernel.org> <04a7465b-ee69-479f-aaa4-ccdf3ae16805@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <04a7465b-ee69-479f-aaa4-ccdf3ae16805@arm.com> On Tue, Mar 10, 2026 at 01:53:21PM +0530, Dev Jain wrote: > So when I was playing around with the code, I noticed that passing > unsigned int nr_pages to add_mm_counter(-nr_pages) messes up things. Then Using int (whether signed or unsigned) to store nr_pages is a bad idea. Look how many people are asking about supporting PUD-sized folios. On an ARM 64k PAGE_SIZE machine, that's 2^26 pages which is uncomfortably close to 2^32. It'll only take one more level to exceed that, so, what, five to ten more years? Just use unsigned long everywhere now and save ourselves the grief later.