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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id n124-20020a817282000000b00573898fb12bsm78328ywc.82.2023.07.23.15.26.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 23 Jul 2023 15:26:13 -0700 (PDT) Date: Sun, 23 Jul 2023 15:26:02 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: Jay Patel , Aneesh Kumar K V , Hugh Dickins , Miaohe Lin , David Hildenbrand , Peter Zijlstra , Yang Shi , Peter Xu , linux-kernel@vger.kernel.org, Song Liu , sparclinux@vger.kernel.org, Alexander Gordeev , Claudio Imbrenda , Will Deacon , linux-s390@vger.kernel.org, Yu Zhao , Ira Weiny , Alistair Popple , Russell King , Matthew Wilcox , Steven Price , Christoph Hellwig , Jason Gunthorpe , linux-arm-kernel@lists.infradead.org, Zi Yan , Huang Ying , Axel Rasmussen , Gerald Schaefer , Christian Borntraeger , Thomas Hellstrom , Ralph Camp bell , Pasha Tatashin , Vasily Gorbik , Anshuman Khandual , Heiko Carstens , Qi Zheng , Suren Baghdasaryan , Vlastimil Babka , SeongJae Park , Lorenzo Stoakes , Jann Horn , linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Naoya Horiguchi , Zack Rusin , Vishal Moola , Minchan Kim , "Kirill A. Shutemov" , Mel Gorman , "David S. Miller" , Mike Rapoport , Mike Kravetz Subject: [PATCH v3 04/13 fix] powerpc: assert_pte_locked() use pte_offset_map_nolock(): fix In-Reply-To: <20230721131341.w5abuxcbohofpzwa@patel> Message-ID: References: <7cd843a9-aa80-14f-5eb2-33427363c20@google.com> <87msztbiy8.fsf@linux.ibm.com> <392f311f-83ac-a5a2-d16e-2c7736d1b577@google.com> <6762c880-6d2b-233f-6786-7ad5b0472dc7@linux.ibm.com> <20230721131341.w5abuxcbohofpzwa@patel> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Aneesh points out that assert_pte_locked() still needs the pmd_none() check, to stop crashing in khugepaged: restore that comment and check. Andrew, when merging with original commit, please edit its 1st para to: Instead of pte_lockptr(), use the recently added pte_offset_map_nolock() in assert_pte_locked(). BUG if pte_offset_map_nolock() fails. Signed-off-by: Hugh Dickins --- arch/powerpc/mm/pgtable.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c index 16b061af86d7..a3dcdb2d5b4b 100644 --- a/arch/powerpc/mm/pgtable.c +++ b/arch/powerpc/mm/pgtable.c @@ -323,6 +323,14 @@ void assert_pte_locked(struct mm_struct *mm, unsigned long addr) pud = pud_offset(p4d, addr); BUG_ON(pud_none(*pud)); pmd = pmd_offset(pud, addr); + /* + * khugepaged to collapse normal pages to hugepage, first set + * pmd to none to force page fault/gup to take mmap_lock. After + * pmd is set to none, we do a pte_clear which does this assertion + * so if we find pmd none, return. + */ + if (pmd_none(*pmd)) + return; pte = pte_offset_map_nolock(mm, pmd, addr, &ptl); BUG_ON(!pte); assert_spin_locked(ptl); -- 2.35.3