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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 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 X-Stat-Signature: b6dnjotxt7txtuirwcea3y3qksa9yn98 X-Rspam-User: X-Rspamd-Queue-Id: 3100D40006 X-Rspamd-Server: rspam07 X-HE-Tag: 1777405565-520759 X-HE-Meta: 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 MESd2Cph SQ+337Zc6xUujDxlO+N0dyw6MqNtwbF0f7samkraKrnvrDasVdd4qZz8h6QvQvuKTel/tr+z99tI48/RPzPx+ucseRwDKJtTqa3XivS7Jj4SJUqu9++42h1LivDod5fYfhhFX2kuCTSHgBW8rsgxmWGGBcajSWvf4TxLJjTOLhjuJDQUVyk3ynvGdmr0Y6QC7eQgNyXQhS6k2ZvzPXGe3iNbbhzcnn+95rR8gzObp3lpSf8WDD/9y9gMaw0qSvxV8+cytauXby7cKlrMhGB6bGIX32g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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