From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f200.google.com (mail-qk0-f200.google.com [209.85.220.200]) by kanga.kvack.org (Postfix) with ESMTP id 818616B0005 for ; Mon, 29 Jan 2018 22:00:14 -0500 (EST) Received: by mail-qk0-f200.google.com with SMTP id k188so5980435qkc.18 for ; Mon, 29 Jan 2018 19:00:14 -0800 (PST) Received: from out3-smtp.messagingengine.com (out3-smtp.messagingengine.com. [66.111.4.27]) by mx.google.com with ESMTPS id b3si3832836qtb.395.2018.01.29.19.00.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 29 Jan 2018 19:00:13 -0800 (PST) From: Zi Yan Subject: [PATCH] Lock mmap_sem when calling migrate_pages() in do_move_pages_to_node() Date: Mon, 29 Jan 2018 22:00:11 -0500 Message-Id: <20180130030011.4310-1-zi.yan@sent.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Michal Hocko , "Kirill A . Shutemov" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Zi Yan From: Zi Yan migrate_pages() requires at least down_read(mmap_sem) to protect related page tables and VMAs from changing. Let's do it in do_page_moves() for both do_move_pages_to_node() and add_page_for_migration(). Also add this lock requirement in the comment of migrate_pages(). Signed-off-by: Zi Yan --- mm/migrate.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 5d0dc7b85f90..52d029953c32 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1354,6 +1354,9 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, * or free list only if ret != 0. * * Returns the number of pages that were not migrated, or an error code. + * + * The caller must hold at least down_read(mmap_sem) for to-be-migrated pages + * to protect related page tables and VMAs from changing. */ int migrate_pages(struct list_head *from, new_page_t get_new_page, free_page_t put_new_page, unsigned long private, @@ -1457,6 +1460,12 @@ static int store_status(int __user *status, int start, int value, int nr) return 0; } +/* + * Migrates the pages from pagelist and put back those not migrated. + * + * The caller must at least hold down_read(mmap_sem), which is required + * for migrate_pages() + */ static int do_move_pages_to_node(struct mm_struct *mm, struct list_head *pagelist, int node) { @@ -1487,7 +1496,6 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, unsigned int follflags; int err; - down_read(&mm->mmap_sem); err = -EFAULT; vma = find_vma(mm, addr); if (!vma || addr < vma->vm_start || !vma_migratable(vma)) @@ -1540,7 +1548,6 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, */ put_page(page); out: - up_read(&mm->mmap_sem); return err; } @@ -1561,6 +1568,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, migrate_prep(); + down_read(&mm->mmap_sem); for (i = start = 0; i < nr_pages; i++) { const void __user *p; unsigned long addr; @@ -1628,6 +1636,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, if (!err) err = err1; out: + up_read(&mm->mmap_sem); return err; } -- 2.15.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org