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 DFD992E737D; Mon, 6 Jul 2026 13:47:50 +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=1783345671; cv=none; b=AuwLvE90sKf5zQSE/oUJNg5N9fci0kTkFYIS1FhvvD0fjxuX0DqJgb6vrelyLMjCIO6WQk0/BFyWGcgO3zrVx5VYmD3BiyFy9WfsqdgHcpEHm1EjUVJGc7d2Y70ThrIpqnyqAJNplnBlQAOHTKL91i5ub0bk8Q4rqBAZh0QS9vg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783345671; c=relaxed/simple; bh=rv8ZKH0Ntfkdd4rrjEmfz3KCubhs6qD6nP4IJFh+yLc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=prlJaJgctAZC5IyNPVYU8aijHAjesRKhd4LJAbHabQIhUxBGX1qjxVwl+Yt49Gt2wWIgHCKEglXpSge8PCt2MNIdu3iDspfbueBhdiOccYwakeaHoqfx7kAfqJ0FoO0S2gns6gmPM79Xade/Ns0isEq6n5eyK/ZWMUTOh2FsK3Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=T7lLSbte; 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="T7lLSbte" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C0A41F00AC4; Mon, 6 Jul 2026 13:47:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783345670; bh=XbPEspgjb9iGcX/qagd/OLVGEsMaq2T5st1yXWGMpXw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=T7lLSbte1fabsTl8bqPNuY+WLRW6VPGciNfEAYPT0untF/dtC13lyqXaIO0GUsbnr XYTVpJJ5iSiIBpBoxy4cw6YQyaZpL+8tqyGQ8Um1dEpjQHgpXD8mWTKuV5TUacGD4V oJ735qQnfjo9RyoPMRCr0PXK0GeQdEC1wR80Tm/f9OCNJr+/bWfPJQAI134iqWkPly Z0K+i2IqKGqfKnpbqJ5B7sITRrsf3hZqa2a1UntZgvnAwrzBx52Ja0uDy8kHmCy9y8 2HxQdNUljStTVdpR6WtuwGU+mGKZQgJwNsmUIO7lNa5o58I0xDcvjxs1nzjJ2RHi92 YsuDksmPhh2Rg== Message-ID: <374a0a2a-444c-412b-8ab8-414dff6a2ca9@kernel.org> Date: Mon, 6 Jul 2026 15:47:43 +0200 Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 2/8] mm: factor zone-device page init helpers out of __init_zone_device_page To: Li Zhe Cc: akpm@linux-foundation.org, apopple@nvidia.com, arnd@arndb.de, bp@alien8.de, dave.hansen@linux.intel.com, kees@kernel.org, linux-arch@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mingo@redhat.com, rppt@kernel.org, tglx@kernel.org, x86@kernel.org References: <38919e81-4c35-4e8b-ba2a-8af8be60b0b6@kernel.org> <20260706115035.49813-1-lizhe.67@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/6/26 13:50, Li Zhe wrote: > On Mon, Jul 6, 2026 at 11:13:45AM +0200, david@kernel.org wrote: > >>> +static inline bool pagemap_resets_refcount(const struct dev_pagemap *pgmap) >>> +{ >>> + /* >>> + * MEMORY_DEVICE_GENERIC pages regain a refcount of 1 in the free >>> + * path. The remaining ZONE_DEVICE types start from 0 here and raise >>> + * the count again when the allocator or driver hands the page out. >>> + */ >>> + switch (pgmap->type) { >>> + case MEMORY_DEVICE_FS_DAX: >>> + case MEMORY_DEVICE_PRIVATE: >>> + case MEMORY_DEVICE_COHERENT: >>> + case MEMORY_DEVICE_PCI_P2PDMA: >>> + return false; >>> + case MEMORY_DEVICE_GENERIC: >>> + return true; >>> + default: >>> + WARN_ONCE(1, "Unknown memory type!"); >>> + return true; >> >> Wouldn't the compiler warn if we would define a new type but forgot to update it >> here? We're using an enum, and I thought the compiler would bail out in that case. >> >> Or are we scared of some other garbage ending up in there? >> >> Apart from that LGTM. > > Thanks. > > I will drop the default case in v6 so a newly added enum memory_type > value is easier to catch during build review. > > I will move the WARN_ONCE() after the switch so we still keep a > runtime guard in case some invalid value ever shows up there. If the compiler complains, we won't need the WARN_ONCE(). -- Cheers, David