Message ID | e51ac0fd-4f96-4728-925-bc54f09ec013@google.com (mailing list archive) |
---|---|
State | Handled Elsewhere, archived |
Headers | show
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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id m19-20020a819e13000000b00560c648ef1esm3382356ywj.72.2023.05.28.23.18.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 28 May 2023 23:18:47 -0700 (PDT) Date: Sun, 28 May 2023 23:18:43 -0700 (PDT) From: Hugh Dickins <hughd@google.com> X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton <akpm@linux-foundation.org> Subject: [PATCH 04/12] powerpc: assert_pte_locked() use pte_offset_map_nolock() In-Reply-To: <35e983f5-7ed3-b310-d949-9ae8b130cdab@google.com> Message-ID: <e51ac0fd-4f96-4728-925-bc54f09ec013@google.com> References: <35e983f5-7ed3-b310-d949-9ae8b130cdab@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org> List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>, <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe> List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev/> List-Post: <mailto:linuxppc-dev@lists.ozlabs.org> List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help> List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>, <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe> Cc: Miaohe Lin <linmiaohe@huawei.com>, David Hildenbrand <david@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Yang Shi <shy828301@gmail.com>, Peter Xu <peterx@redhat.com>, Song Liu <song@kernel.org>, sparclinux@vger.kernel.org, Alexander Gordeev <agordeev@linux.ibm.com>, Claudio Imbrenda <imbrenda@linux.ibm.com>, Will Deacon <will@kernel.org>, linux-s390@vger.kernel.org, Yu Zhao <yuzhao@google.com>, Ira Weiny <ira.weiny@intel.com>, Alistair Popple <apopple@nvidia.com>, Russell King <linux@armlinux.org.uk>, Matthew Wilcox <willy@infradead.org>, Steven Price <steven.price@arm.com>, Christoph Hellwig <hch@infradead.org>, Jason Gunthorpe <jgg@ziepe.ca>, "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>, Axel Rasmussen <axelrasmussen@google.com>, Christian Borntraeger <borntraeger@linux.ibm.com>, Thomas Hellstrom <thomas.hellstrom@linux.intel.com>, Ralph Campbell <rcampbell@nvidia.com>, Pasha Tatashin <pasha.tatashin@soleen.com>, Anshuman Khandual <anshuman.khandual@arm.com>, Heiko Ca rstens <hca@linux.ibm.com>, Qi Zheng <zhengqi.arch@bytedance.com>, Suren Baghdasaryan <surenb@google.com>, linux-arm-kernel@lists.infradead.org, SeongJae Park <sj@kernel.org>, Jann Horn <jannh@google.com>, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Naoya Horiguchi <naoya.horiguchi@nec.com>, linux-kernel@vger.kernel.org, Minchan Kim <minchan@kernel.org>, Mike Rapoport <rppt@kernel.org>, Mel Gorman <mgorman@techsingularity.net>, "David S. Miller" <davem@davemloft.net>, Zack Rusin <zackr@vmware.com>, Mike Kravetz <mike.kravetz@oracle.com> Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" <linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org> |
Series |
mm: free retracted page table by RCU
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expand
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diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c index cb2dcdb18f8e..16b061af86d7 100644 --- a/arch/powerpc/mm/pgtable.c +++ b/arch/powerpc/mm/pgtable.c @@ -311,6 +311,8 @@ void assert_pte_locked(struct mm_struct *mm, unsigned long addr) p4d_t *p4d; pud_t *pud; pmd_t *pmd; + pte_t *pte; + spinlock_t *ptl; if (mm == &init_mm) return; @@ -321,16 +323,10 @@ 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; - BUG_ON(!pmd_present(*pmd)); - assert_spin_locked(pte_lockptr(mm, pmd)); + pte = pte_offset_map_nolock(mm, pmd, addr, &ptl); + BUG_ON(!pte); + assert_spin_locked(ptl); + pte_unmap(pte); } #endif /* CONFIG_DEBUG_VM */
Instead of pte_lockptr(), use the recently added pte_offset_map_nolock() in assert_pte_locked(). BUG if pte_offset_map_nolock() fails: this is stricter than the previous implementation, which skipped when pmd_none() (with a comment on khugepaged collapse transitions): but wouldn't we want to know, if an assert_pte_locked() caller can be racing such transitions? This mod might cause new crashes: which either expose my ignorance, or indicate issues to be fixed, or limit the usage of assert_pte_locked(). Signed-off-by: Hugh Dickins <hughd@google.com> --- arch/powerpc/mm/pgtable.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-)