From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta0.migadu.com (out-186.mta0.migadu.com [91.218.175.186]) (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 B1968327A0C for ; Mon, 15 Sep 2025 14:27:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757946424; cv=none; b=IvnqomoZtXNIlyeeYvvSZ4TC0BqYPCwHTzc9iWvlvo5xiap9hXHWTbb3sL7kw2gE132p0U1VWYu+qwiIkPUiwv8T1+L+1evWo4vkOD0OUSPkBsFkWfyAhrgRIh2eRg42xsbCMdz7nbAILh0bLgmzWaHlRuBRtA49X/WfcEG4LFE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757946424; c=relaxed/simple; bh=4kDRsdMHX+x78ly2T+SWI794hARsVpUs1q8YjwbxA9A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=L+bnSE+UKscdYf/a1QM/ocn+EP1u6w7GyXNJN1UKdw1vF+A1RexsuI9kkPNaP5pH/QA1uTjcZfXm/VrsKSrzE/2VESSHNetFlhRnEcd1Jz4/ysUIZM0c3DaknbZGPqtS0L/Wex8YHNWR9nlTG2ePKK4TPGjZn4S/uUQj/tHPV3E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=RMtWfSvN; arc=none smtp.client-ip=91.218.175.186 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="RMtWfSvN" Message-ID: <4ee7a430-f92d-409b-89a8-f084605eda98@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1757946419; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YAWgOkmD5YFn/glj5ESxRFYtDt9wouSNosBxkMLToC4=; b=RMtWfSvN2qkTyq23TvknU+5jvUqth0eJ3sjEEUmnn10qqNEr6tx9r+h0yY6RMyv1kCk0r4 zIyPO366ZYwoY+5zfGRmEq3DkpIg3KMU79RepORdOGYx5bnKvzJ05r4u3mgoznxoLYHDSH 2oZZ2LDu6Zv8X1czsurKsRzk4EJeSoY= Date: Mon, 15 Sep 2025 22:26:51 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH mm-new 2/3] mm: clean up and expose is_guard_pte_marker() Content-Language: en-US To: Lorenzo Stoakes Cc: akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, ioworker0@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Kairui Song References: <20250914143547.27687-1-lance.yang@linux.dev> <20250914143547.27687-3-lance.yang@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Hi Lorenzo, Thanks for taking time to review! On 2025/9/15 21:54, Lorenzo Stoakes wrote: > On Sun, Sep 14, 2025 at 10:35:46PM +0800, Lance Yang wrote: >> From: Lance Yang >> >> is_guard_pte_marker() performs a redundant check because it calls both >> is_pte_marker() and is_guard_swp_entry(), both of which internally check >> for a PTE marker. >> >> is_guard_pte_marker() >> |- is_pte_marker() >> | `- is_pte_marker_entry() // First check >> `- is_guard_swp_entry() >> `- is_pte_marker_entry() // Second, redundant check >> > > I mean, it expands to: > > is_swap_pte(pte) && is_pte_marker_entry(pte_to_swp_entry(pte)) && > is_pte_marker_entry(pte_to_swp_entry(pte)) Yes, that's a much clearer way to lay it out ;) > > So I don't think it's really unreasonable to expect compiler magic here... > > But you're right that I should have just used is_swap_pte() really, it's a bit > silly not to, so this is fine :) Exactly. Glad we're on the same page! > >> While a modern compiler could likely optimize this away, let's have clean >> code and not rely on it ;) > > Please don't put smileys in commit messages :) as cute as they are, this is > going on the permanent kernel record and while we all love them, it's > probably not the best place to put them :P > >> >> Also, make it available for hugepage collapsing code. > > Nit but put a newline after this. Got it. Will fix up all nits in v2. > > I think probably if I'm really really nitty I'd say that you should put > this bit first, as it's the primary motivation for the change, and put the > refactoring stuff after. Ah, right. The motivation for exposing the helper should come first. I'll reorder this changelog in v2. > >> Cc: Kairui Song >> Signed-off-by: Lance Yang > > This seems fine to me, so: > > Reviewed-by: Lorenzo Stoakes Thanks, Lance > >> --- >> include/linux/swapops.h | 6 ++++++ >> mm/madvise.c | 6 ------ >> 2 files changed, 6 insertions(+), 6 deletions(-) >> >> diff --git a/include/linux/swapops.h b/include/linux/swapops.h >> index 59c5889a4d54..7f5684fa043b 100644 >> --- a/include/linux/swapops.h >> +++ b/include/linux/swapops.h >> @@ -469,6 +469,12 @@ static inline int is_guard_swp_entry(swp_entry_t entry) >> (pte_marker_get(entry) & PTE_MARKER_GUARD); >> } >> >> +static inline bool is_guard_pte_marker(pte_t ptent) >> +{ >> + return is_swap_pte(ptent) && >> + is_guard_swp_entry(pte_to_swp_entry(ptent)); >> +} >> + >> /* >> * This is a special version to check pte_none() just to cover the case when >> * the pte is a pte marker. It existed because in many cases the pte marker >> diff --git a/mm/madvise.c b/mm/madvise.c >> index 35ed4ab0d7c5..bd46e6788fac 100644 >> --- a/mm/madvise.c >> +++ b/mm/madvise.c >> @@ -1069,12 +1069,6 @@ static bool is_valid_guard_vma(struct vm_area_struct *vma, bool allow_locked) >> return !(vma->vm_flags & disallowed); >> } >> >> -static bool is_guard_pte_marker(pte_t ptent) >> -{ >> - return is_pte_marker(ptent) && >> - is_guard_swp_entry(pte_to_swp_entry(ptent)); >> -} >> - >> static int guard_install_pud_entry(pud_t *pud, unsigned long addr, >> unsigned long next, struct mm_walk *walk) >> { >> -- >> 2.49.0 >>