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Fri, 17 Jul 2026 13:32:22 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.87.85.9]) by smtpav02.fra02v.mail.ibm.com (Postfix) with SMTP; Fri, 17 Jul 2026 13:32:22 +0000 (GMT) Received: by tuxmaker.boeblingen.de.ibm.com (Postfix, from userid 55669) id 9B59F16274F; Fri, 17 Jul 2026 15:32:22 +0200 (CEST) From: Alexander Gordeev To: Kevin Brodsky , David Hildenbrand , Chris Li , Gerald Schaefer , Heiko Carstens , Christian Borntraeger , Claudio Imbrenda Cc: linux-s390@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-sparse@vger.kernel.org Subject: [RFC PATCH 2/4] mm: introduce ptep_get_nopgtable() and set_pte_nopgtable() accessors Date: Fri, 17 Jul 2026 15:32:20 +0200 Message-ID: <19627b802d38510a6e006ec666d3177278ad8a38.1784292223.git.agordeev@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: bRWCLk7W3ROJPEtFwpDR_wlth4pH6ZxY X-Proofpoint-Spam-Info: AW1haW4tMjYwNzE3MDEzNCBTYWx0ZWRfXxNKXxRcRZm3U kzCrK3ojC+2IsC3lmACZA/WyTynT9SOY5Qp3aeeuxdxqascRVXrFlIxGMVpLEiuelphupdK8A5I DXwpbiTBDVJjp86tYDyZn5G7x8seu/s= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzE3MDEzNCBTYWx0ZWRfXx4TnIy60KXIX ZxD1RKv9CV8do+R8VJYpfLh/dcd0bftB/N3ViHaEoR602zf4SOc7KkfD1b3oeCNH3mS31G7+wMO zcZ1Ob0Lmbrm9h9wj7bT0RdzqF4EezOTZzpT0Mg6SIGQJWV82zUXwy0LpSFVsDaggyrC7Tv8Gnv OuvpZu9XpRCYBowaH+8MmA4oliKFB6b6svxrf5QyE0hZkI+qYD5AwioPA+p4PJRkDs2PsByVSsR n5+JHDpI4DrgBj5ab/QQydUR7ajzt51m8De06kbY+GFh4sakHArgD15OwnPxKUG0zdih68IFpcK MCSdWTBgu9n9m8o4jUoAF/nA9t09f0RAAt7xCZYx1kk7Xlv8qXN842GH4C/qmE0SYw+7KaQPAs2 vXKkbEBa0Dx8WYrToDj4bYPOto6CcoZClENOMo/ZulJoHO40OWl9Htj8c0RFfOdBVpov497PrLz XG26QYxSl0bTyaelYhw== X-Authority-Analysis: v=2.4 cv=XbS5Co55 c=1 sm=1 tr=0 ts=6a5a2eec cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=uWIZLCJMPdl43Pu2rEcA:9 X-Proofpoint-ORIG-GUID: bRWCLk7W3ROJPEtFwpDR_wlth4pH6ZxY X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-17_03,2026-07-17_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 spamscore=0 phishscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 malwarescore=0 impostorscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607170134 Add helpers to safely access PTE values stored outside page tables, such as in stack variables or temporary copies. These adopt the check from folio_pte_batch_flags() to ensure the pointer does not point into an actual page table. Follow the pattern established by commit c33c794828f2 ("mm: ptep_get() conversion") and use the new accessors instead of direct pointer dereferences. Signed-off-by: Alexander Gordeev --- include/linux/pgtable.h | 25 +++++++++++++++++++++++++ mm/internal.h | 16 ++++++---------- mm/ksm.c | 2 +- 3 files changed, 32 insertions(+), 11 deletions(-) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 2981e386da7b..e38f045d0e73 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -489,6 +489,31 @@ static inline int pudp_set_access_flags(struct vm_ar= ea_struct *vma, #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif =20 +#ifndef ptep_get_nopgtable +static inline pte_t ptep_get_nopgtable(pte_t *ptep) +{ + /* + * Ensure this is a pointer to a copy not a pointer into a page table. + * If this is a stack value, it won't be a valid virtual address, but + * that's fine because it also cannot be pointing into the page table. + */ + VM_WARN_ON(virt_addr_valid(ptep) && PageTable(virt_to_page(ptep))); + + return *ptep; +} +#endif + +#ifndef set_pte_nopgtable +static inline void set_pte_nopgtable(pte_t *ptep, pte_t pte) +{ + /* + * See comment in ptep_get_nopgtable(). + */ + VM_WARN_ON(virt_addr_valid(ptep) && PageTable(virt_to_page(ptep))); + *ptep =3D pte; +} +#endif + #ifndef ptep_get static inline pte_t ptep_get(pte_t *ptep) { diff --git a/mm/internal.h b/mm/internal.h index 181e79f1d6a2..0d04a107962a 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -339,18 +339,12 @@ static inline unsigned int folio_pte_batch_flags(st= ruct folio *folio, unsigned int max_nr, fpb_t flags) { bool any_writable =3D false, any_young =3D false, any_dirty =3D false; - pte_t expected_pte, pte =3D *ptentp; + pte_t expected_pte, pte =3D ptep_get_nopgtable(ptentp); unsigned int nr, cur_nr; =20 VM_WARN_ON_FOLIO(!pte_present(pte), folio); VM_WARN_ON_FOLIO(!folio_test_large(folio) || max_nr < 1, folio); VM_WARN_ON_FOLIO(page_folio(pfn_to_page(pte_pfn(pte))) !=3D folio, foli= o); - /* - * Ensure this is a pointer to a copy not a pointer into a page table. - * If this is a stack value, it won't be a valid virtual address, but - * that's fine because it also cannot be pointing into the page table. - */ - VM_WARN_ON(virt_addr_valid(ptentp) && PageTable(virt_to_page(ptentp))); =20 /* Limit max_nr to the actual remaining PFNs in the folio we could batc= h. */ max_nr =3D min_t(unsigned long, max_nr, @@ -379,12 +373,14 @@ static inline unsigned int folio_pte_batch_flags(st= ruct folio *folio, nr +=3D cur_nr; } =20 + pte =3D ptep_get_nopgtable(ptentp); if (any_writable) - *ptentp =3D pte_mkwrite(*ptentp, vma); + pte =3D pte_mkwrite(pte, vma); if (any_young) - *ptentp =3D pte_mkyoung(*ptentp); + pte =3D pte_mkyoung(pte); if (any_dirty) - *ptentp =3D pte_mkdirty(*ptentp); + pte =3D pte_mkdirty(pte); + set_pte_nopgtable(ptentp, pte); =20 return min(nr, max_nr); } diff --git a/mm/ksm.c b/mm/ksm.c index 7d5b76478f0b..5b22c602a105 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1352,7 +1352,7 @@ static int write_protect_page(struct vm_area_struct= *vma, struct folio *folio, =20 set_pte_at(mm, pvmw.address, pvmw.pte, entry); } - *orig_pte =3D entry; + set_pte_nopgtable(orig_pte, entry); err =3D 0; =20 out_unlock: --=20 2.53.0