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 6A557282F1F; Tue, 28 Apr 2026 19:46:05 +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=1777405565; cv=none; b=p40oVNY9DQOE+O9eoyL7Ao7r+FQqcE7UDUuhu6KeBJXnufAfU7Ru4pFysAHhz0H7+Ip62507ycjkOt8WypG68d5gZl3Rs49bo4h2u/qLYVbY1/+WVNd+9orhFiPXRLd8Zms5x58BkiSf6rj5H78DK2NALoQa2otXj5CbAIyukr0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777405565; c=relaxed/simple; bh=yvm5AAW8pWe+hcrCUl/s0FLrh+xzKGKcVtjKj0e9BOU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TokSJCLc5nXDJ/pP2uDpQfGqzM1OG+drD6q4do7bibIEZZIuD5qqs1DJIVU3Cb3CJhRpOTt9CNpdlLly+n0KTNBBrzDn0Bw1/btsQIxzoPIcNlvft1gYLhxm+bH5YtvipGhGNSd1Y00X3y4vsCFJceZPhvSsya1I8Y9fNw/xtX4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ik8AqnBV; 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="ik8AqnBV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A6B5C2BCAF; Tue, 28 Apr 2026 19:46:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777405565; bh=yvm5AAW8pWe+hcrCUl/s0FLrh+xzKGKcVtjKj0e9BOU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ik8AqnBVEniWxz4gB+Db0JUp63he0UIJizJ+2MIrottcKhFRnNIhICcF7fZYkOTLT CkghgSUxL+v5S8q7MdGMtKP0YjSBbTlje+3MaZgwaqY3sxmf8BcLxNtIyUngHjf5wU p6rZEuKr0hDBjEwMBgrw6ZsZWJFxgvVv5i9eh+tY07iXVNWMNUdWfXx3dZvxGp/JLv XplyZYFhpqE3ivl15eC9v4gizmathKxxt7/qBOUJ2juHfIxO8X7BJEUQ62YoqM1N6o OxAy1fbz4I1nFX0IaT3Q9vG5/iRxE8/kKgem3VJbjxNSBSfVvzP84rS411M9fDIKwC U80q4+bXXrHzw== Message-ID: <5f45cc59-d71f-409c-8cfb-6eba23b0a447@kernel.org> Date: Tue, 28 Apr 2026 21:45:59 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/gup: cleanup pgtable entry accessors To: Alexander Gordeev , Kevin Brodsky , Ryan Roberts , Andrew Morton Cc: linux-s390@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Gerald Schaefer , Heiko Carstens , Vasily Gorbik References: <20260421051754.1691221-1-agordeev@linux.ibm.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 4/21/26 07:17, Alexander Gordeev wrote: > PMD and PUD entries revalidation has the same semantics as PTE entry > revalidation. Convert the remaining direct entry dereferences to the > corresponding accessors. > > The PTE validation in gup_fast_pte_range() is inconsistent with the > prior value acquisition in the sense that it drops the lockless > access semantics. > > Use the lockless accessor not only for the PTE, but also for the PMD > validation, which is likewise inconsistent with the prior value > acquisition in gup_fast_pmd_range(). > > Signed-off-by: Alexander Gordeev > --- > mm/gup.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index 8e7dc2c6ee73..236450feea9a 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2865,8 +2865,8 @@ static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, > if (!folio) > goto pte_unmap; > > - if (unlikely(pmd_val(pmd) != pmd_val(*pmdp)) || > - unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) { > + if (unlikely(pmd_val(pmd) != pmd_val(pmdp_get_lockless(pmdp))) || > + unlikely(pte_val(pte) != pte_val(ptep_get_lockless(ptep)))) { > gup_put_folio(folio, 1, flags); > goto pte_unmap; > } > @@ -2942,7 +2942,7 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr, > if (!folio) > return 0; > > - if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { > + if (unlikely(pmd_val(orig) != pmd_val(pmdp_get_lockless(pmdp)))) { > gup_put_folio(folio, refs, flags); > return 0; > } > @@ -2985,7 +2985,7 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr, > if (!folio) > return 0; > > - if (unlikely(pud_val(orig) != pud_val(*pudp))) { > + if (unlikely(pud_val(orig) != pud_val(pudp_get(pudp)))) { > gup_put_folio(folio, refs, flags); > return 0; > } In general, LGTM. I do wonder, though, if we want to switch to pte_same/pmd_same/pud_same while at it? -- Cheers, David