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 6D57038C429 for ; Thu, 16 Apr 2026 19:44:22 +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=1776368662; cv=none; b=BTKWqyYTOYJ4m3zjwhXPzJ8Sa3AhMq61sIEtJP8+kvjLnCJz2onr8ansfuepVftsGtbR1/iczHP7QNm7tAYMOE0TInKgbRpiitVuQ65uzqXFtUk2ugjXa5ACTAZtxHsx/2G6Y9FTe+yPmf/6cm0hEYEYSjLQHHMOwj/TnNDKqnA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776368662; c=relaxed/simple; bh=qKg59kcnzqTeEd7CQvgz5TtsXwNQ7XFtrOnNy0VMoCY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=spU6PiSEU3GznShHE4xsz2ZVHPEWc15uhlQlm5uVEdeLK33X00hRFjD2PVSJ6yDK7GoKDaQQHcpPJhUPy0mU5+PANM7I3FVy4DrdqE/hn7z9yDJjZsq+BdaOx1Ys+hanbc2vKxOqny1IFBOhuEQcys7LpdXb0UCCfXd7BD+z4a8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=srQ8xjnM; 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="srQ8xjnM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37693C2BCAF; Thu, 16 Apr 2026 19:44:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776368660; bh=qKg59kcnzqTeEd7CQvgz5TtsXwNQ7XFtrOnNy0VMoCY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=srQ8xjnMI5SNpZdbXO6SJXbCmehgQkh2pbyde5HNlB/onKRp9eeuD63KLLHIPQGSr ppK0GBStIybMhEfEWTbwxjDRE+/Js92e8OmF8PBO4CyJVqu9T1Hk0/PT9vybrnsQji PORhcHBKPLGg4WNV2oormglm1T6i2JAJrt3Gaq4Ts42UbYtKM7CplSgzVsQ5SjEt95 lz6Im6gzfU6l0pSWoUBGLMQUWMR8+AgcD303MMmfI7tbzmwL1LK85GbfyVRs0JbNc/ gsKg07U0qm+fK/QBHu5tmkYfqzKLeqpDK4kNtJTYJjpCRLvPyC6KeXrzyq9nkJx6WL C4Y826JVqRsdw== Message-ID: Date: Thu, 16 Apr 2026 21:44:15 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/migrate_device: Cleanup up PMD Checks and warnings To: Sunny Patel Cc: Andrew Morton , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260414141344.29949-1-nueralspacetech@gmail.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 4/14/26 16:13, Sunny Patel wrote: > Remove the odd VM_WARN_ON_FOLIO(!folio, folio) usage and replace it > with a simpler VM_WARN_ON_ONCE(!folio) check. > > Drop the redundant VM_WARN_ON_ONCE(!pmd_none(*pmdp) && > !is_huge_zero_pmd(*pmdp)). > > Refactor the PMD checks to use pmd_present(), making the control flow > clearer and avoiding duplicate condition checks. > > Signed-off-by: Sunny Patel > --- > mm/migrate_device.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/migrate_device.c b/mm/migrate_device.c > index 8079676c8f1f..fe1c1999aa2d 100644 > --- a/mm/migrate_device.c > +++ b/mm/migrate_device.c > @@ -807,8 +807,7 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, > bool flush = false; > unsigned long i; > > - VM_WARN_ON_FOLIO(!folio, folio); > - VM_WARN_ON_ONCE(!pmd_none(*pmdp) && !is_huge_zero_pmd(*pmdp)); > + VM_WARN_ON_ONCE(!folio); I'd test for "page" here instead. But it doesn't matter as of today. > > if (!thp_vma_suitable_order(vma, addr, HPAGE_PMD_ORDER)) > return -EINVAL; > @@ -865,12 +864,13 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, > if (userfaultfd_missing(vma)) > goto unlock_abort; > > - if (!pmd_none(*pmdp)) { > + if (pmd_present(*pmdp)) { > if (!is_huge_zero_pmd(*pmdp)) > goto unlock_abort; > flush = true; > - } else if (!pmd_none(*pmdp)) > + } else if (!pmd_none(*pmdp)) { > goto unlock_abort; > + } > > add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); > folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE); is_huge_zero_pmd() checks pmd_present(), so we didn't have a bug before. We could also do: if (is_huge_zero_pmd(*pmdp)) { flush = true; } else if (!pmd_none(*pmdp)) { goto unlock_abort; } But I don't particularly care Acked-by: David Hildenbrand (Arm) -- Cheers, David