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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id r205-20020a0de8d6000000b00559d9989490sm304902ywe.41.2023.06.08.18.41.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jun 2023 18:41:34 -0700 (PDT) Date: Thu, 8 Jun 2023 18:41:31 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Ryan Roberts , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 26/32] mm/huge_memory: split huge pmd under one pte_offset_map() In-Reply-To: Message-ID: <90cbed7f-90d9-b779-4a46-d2485baf9595@google.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 5C3B24000F X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 7prksha9ia1w8bcodih7c3n655jgdkyx X-HE-Tag: 1686274897-945784 X-HE-Meta: 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 XHxM8Mne lLuW63DQ8yrMRcTrzRPTZ1BQPWzulF0J/6XgetAp65/pMcIrU+B2eDndhQjN+vgoiCvPwawK637+AJ0bbmRVnnsyFg6IgtYOa7x5Ii12BEfsidRTFtfA4k6MVp39VqkKD6vGNIc2xPEBF2c/2dQX0GNLV3XYyUA2wO4g3kwk+iTzN0uurTcQhK6Zi8LaYqHhiw2qV2S1b9xbAUsEyWSw2hnrTaZ/uzyrRlOECBT8WjelgoeeAoryL3GtjyYv4PqzxjUwemF87fDgX0rN0xXTqIGZJJ709cwUc8TPWwWo4jQwpU5xVWO9xzcWQHQzTDUIb+IHm9WPUSwIN3ci/vD/ALhmmlihTeZ9KhCWIDGIc39knn9Ztn2Nsyg2Zk+KlLZXaEQrwCkEyb4W67Cg5bMF69jiZfs3TT69RcWms/6Btsk2w8fvIYePgqRE47qMWrzFXyoBNyGaUoqU6jMU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: __split_huge_zero_page_pmd() use a single pte_offset_map() to sweep the extent: it's already under pmd_lock(), so this is no worse for latency; and since it's supposed to have full control of the just-withdrawn page table, here choose to VM_BUG_ON if it were to fail. And please don't increment haddr by PAGE_SIZE, that should remain huge aligned: declare a separate addr (not a bugfix, but it was deceptive). __split_huge_pmd_locked() likewise (but it had declared a separate addr); and change its BUG_ON(!pte_none) to VM_BUG_ON, for consistency with zero (those deposited page tables are sometimes victims of random corruption). Signed-off-by: Hugh Dickins Reviewed-by: Yang Shi --- mm/huge_memory.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d4bd5fa7c823..839c13fa0bbe 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2037,6 +2037,8 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, struct mm_struct *mm = vma->vm_mm; pgtable_t pgtable; pmd_t _pmd, old_pmd; + unsigned long addr; + pte_t *pte; int i; /* @@ -2052,17 +2054,20 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, pgtable = pgtable_trans_huge_withdraw(mm, pmd); pmd_populate(mm, &_pmd, pgtable); - for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { - pte_t *pte, entry; - entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); + pte = pte_offset_map(&_pmd, haddr); + VM_BUG_ON(!pte); + for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { + pte_t entry; + + entry = pfn_pte(my_zero_pfn(addr), vma->vm_page_prot); entry = pte_mkspecial(entry); if (pmd_uffd_wp(old_pmd)) entry = pte_mkuffd_wp(entry); - pte = pte_offset_map(&_pmd, haddr); VM_BUG_ON(!pte_none(*pte)); - set_pte_at(mm, haddr, pte, entry); - pte_unmap(pte); + set_pte_at(mm, addr, pte, entry); + pte++; } + pte_unmap(pte - 1); smp_wmb(); /* make pte visible before pmd */ pmd_populate(mm, pmd, pgtable); } @@ -2077,6 +2082,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; bool anon_exclusive = false, dirty = false; unsigned long addr; + pte_t *pte; int i; VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); @@ -2205,8 +2211,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, pgtable = pgtable_trans_huge_withdraw(mm, pmd); pmd_populate(mm, &_pmd, pgtable); + pte = pte_offset_map(&_pmd, haddr); + VM_BUG_ON(!pte); for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { - pte_t entry, *pte; + pte_t entry; /* * Note that NUMA hinting access restrictions are not * transferred to avoid any possibility of altering @@ -2249,11 +2257,11 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, entry = pte_mkuffd_wp(entry); page_add_anon_rmap(page + i, vma, addr, false); } - pte = pte_offset_map(&_pmd, addr); - BUG_ON(!pte_none(*pte)); + VM_BUG_ON(!pte_none(*pte)); set_pte_at(mm, addr, pte, entry); - pte_unmap(pte); + pte++; } + pte_unmap(pte - 1); if (!pmd_migration) page_remove_rmap(page, vma, true); -- 2.35.3