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Thu, 18 Jun 2020 15:05:18 -0700 (PDT) Received: from phantasmagoria.svl.corp.google.com ([2620:15c:2c4:201:2b0a:8c1:6a84:1aa0]) by smtp.gmail.com with ESMTPSA id 125sm3634484pff.130.2020.06.18.15.05.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Jun 2020 15:05:18 -0700 (PDT) From: Arjun Roy To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: arjunroy@google.com, edumazet@google.com, hughd@google.com, rientjes@google.com, soheil@google.com Subject: [mm] mm/memory.c: Properly pte_offset_map_lock/unlock in vm_insert_pages. Date: Thu, 18 Jun 2020 15:04:46 -0700 Message-Id: <20200618220446.20284-1-arjunroy.kdev@gmail.com> X-Mailer: git-send-email 2.27.0.111.gc72c7da667-goog MIME-Version: 1.0 X-Rspamd-Queue-Id: D4B3A1819B12A X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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: From: Arjun Roy Calls to pte_offset_map() in vm_insert_pages() are erroneously not matched with a call to pte_unmap(). This would cause problems on architectures where that is not a no-op. This patch does away with the non-traditional locking in the existing code, and instead uses pte_offset_map_lock/unlock() as usual, incrementing PTE as necessary. The PTE pointer is kept within bounds since we clamp it with PTRS_PER_PTE. Fixes: 8cd3984d81d5 ("mm/memory.c: add vm_insert_pages()") Signed-off-by: Arjun Roy Acked-by: David Rientjes --- mm/memory.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index fd5350cce71a..9f44a7af8dbc 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1498,7 +1498,7 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr, } #ifdef pte_index -static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd, +static int insert_page_in_batch_locked(struct mm_struct *mm, pte_t *pte, unsigned long addr, struct page *page, pgprot_t prot) { int err; @@ -1506,8 +1506,9 @@ static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd, if (!page_count(page)) return -EINVAL; err = validate_page_before_insert(page); - return err ? err : insert_page_into_pte_locked( - mm, pte_offset_map(pmd, addr), addr, page, prot); + if (err) + return err; + return insert_page_into_pte_locked(mm, pte, addr, page, prot); } /* insert_pages() amortizes the cost of spinlock operations @@ -1517,7 +1518,8 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr, struct page **pages, unsigned long *num, pgprot_t prot) { pmd_t *pmd = NULL; - spinlock_t *pte_lock = NULL; + pte_t *start_pte, *pte; + spinlock_t *pte_lock; struct mm_struct *const mm = vma->vm_mm; unsigned long curr_page_idx = 0; unsigned long remaining_pages_total = *num; @@ -1536,18 +1538,17 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr, ret = -ENOMEM; if (pte_alloc(mm, pmd)) goto out; - pte_lock = pte_lockptr(mm, pmd); while (pages_to_write_in_pmd) { int pte_idx = 0; const int batch_size = min_t(int, pages_to_write_in_pmd, 8); - spin_lock(pte_lock); - for (; pte_idx < batch_size; ++pte_idx) { - int err = insert_page_in_batch_locked(mm, pmd, + start_pte = pte_offset_map_lock(mm, pmd, addr, &pte_lock); + for (pte = start_pte; pte_idx < batch_size; ++pte, ++pte_idx) { + int err = insert_page_in_batch_locked(mm, pte, addr, pages[curr_page_idx], prot); if (unlikely(err)) { - spin_unlock(pte_lock); + pte_unmap_unlock(start_pte, pte_lock); ret = err; remaining_pages_total -= pte_idx; goto out; @@ -1555,7 +1556,7 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr, addr += PAGE_SIZE; ++curr_page_idx; } - spin_unlock(pte_lock); + pte_unmap_unlock(start_pte, pte_lock); pages_to_write_in_pmd -= batch_size; remaining_pages_total -= batch_size; }