From: Nadav Amit <namit@vmware.com> To: <linux-mm@kvack.org> Cc: <nadav.amit@gmail.com>, <linux-kernel@vger.kernel.org>, <akpm@linux-foundation.org>, Nadav Amit <namit@vmware.com>, Minchan Kim <minchan@kernel.org>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Andy Lutomirski <luto@kernel.org> Subject: [PATCH v6 3/7] Revert "mm: numa: defer TLB flush for THP migration as long as possible" Date: Tue, 1 Aug 2017 17:08:14 -0700 [thread overview] Message-ID: <20170802000818.4760-4-namit@vmware.com> (raw) In-Reply-To: <20170802000818.4760-1-namit@vmware.com> While deferring TLB flushes is a good practice, the reverted patch caused pending TLB flushes to be checked while the page-table lock is not taken. As a result, in architectures with weak memory model (PPC), Linux may miss a memory-barrier, miss the fact TLB flushes are pending, and cause (in theory) a memory corruption. Since the alternative of using smp_mb__after_unlock_lock() was considered a bit open-coded, and the performance impact is expected to be small, the previous patch is reverted. This reverts commit b0943d61b8fa420180f92f64ef67662b4f6cc493. Suggested-by: Mel Gorman <mgorman@suse.de> Cc: Minchan Kim <minchan@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Andy Lutomirski <luto@kernel.org> Signed-off-by: Nadav Amit <namit@vmware.com> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com> --- mm/huge_memory.c | 7 +++++++ mm/migrate.c | 6 ------ 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 88c6167f194d..b51d83e410eb 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1496,6 +1496,13 @@ int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) } /* + * The page_table_lock above provides a memory barrier + * with change_protection_range. + */ + if (mm_tlb_flush_pending(vma->vm_mm)) + flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); + + /* * Migrate the THP to the requested node, returns with page unlocked * and access rights restored. */ diff --git a/mm/migrate.c b/mm/migrate.c index 89a0a1707f4c..1f6c2f41b3cb 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1935,12 +1935,6 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm, put_page(new_page); goto out_fail; } - /* - * We are not sure a pending tlb flush here is for a huge page - * mapping or not. Hence use the tlb range variant - */ - if (mm_tlb_flush_pending(mm)) - flush_tlb_range(vma, mmun_start, mmun_end); /* Prepare a page as a migration target */ __SetPageLocked(new_page); -- 2.11.0
WARNING: multiple messages have this Message-ID (diff)
From: Nadav Amit <namit@vmware.com> To: linux-mm@kvack.org Cc: nadav.amit@gmail.com, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Nadav Amit <namit@vmware.com>, Minchan Kim <minchan@kernel.org>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Andy Lutomirski <luto@kernel.org> Subject: [PATCH v6 3/7] Revert "mm: numa: defer TLB flush for THP migration as long as possible" Date: Tue, 1 Aug 2017 17:08:14 -0700 [thread overview] Message-ID: <20170802000818.4760-4-namit@vmware.com> (raw) In-Reply-To: <20170802000818.4760-1-namit@vmware.com> While deferring TLB flushes is a good practice, the reverted patch caused pending TLB flushes to be checked while the page-table lock is not taken. As a result, in architectures with weak memory model (PPC), Linux may miss a memory-barrier, miss the fact TLB flushes are pending, and cause (in theory) a memory corruption. Since the alternative of using smp_mb__after_unlock_lock() was considered a bit open-coded, and the performance impact is expected to be small, the previous patch is reverted. This reverts commit b0943d61b8fa420180f92f64ef67662b4f6cc493. Suggested-by: Mel Gorman <mgorman@suse.de> Cc: Minchan Kim <minchan@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Andy Lutomirski <luto@kernel.org> Signed-off-by: Nadav Amit <namit@vmware.com> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com> --- mm/huge_memory.c | 7 +++++++ mm/migrate.c | 6 ------ 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 88c6167f194d..b51d83e410eb 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1496,6 +1496,13 @@ int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) } /* + * The page_table_lock above provides a memory barrier + * with change_protection_range. + */ + if (mm_tlb_flush_pending(vma->vm_mm)) + flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); + + /* * Migrate the THP to the requested node, returns with page unlocked * and access rights restored. */ diff --git a/mm/migrate.c b/mm/migrate.c index 89a0a1707f4c..1f6c2f41b3cb 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1935,12 +1935,6 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm, put_page(new_page); goto out_fail; } - /* - * We are not sure a pending tlb flush here is for a huge page - * mapping or not. Hence use the tlb range variant - */ - if (mm_tlb_flush_pending(mm)) - flush_tlb_range(vma, mmun_start, mmun_end); /* Prepare a page as a migration target */ __SetPageLocked(new_page); -- 2.11.0 -- 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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-08-02 7:33 UTC|newest] Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-08-02 0:08 [PATCH v6 0/7] fixes of TLB batching races Nadav Amit 2017-08-02 0:08 ` Nadav Amit 2017-08-02 0:08 ` [PATCH v6 1/7] mm: migrate: prevent racy access to tlb_flush_pending Nadav Amit 2017-08-02 0:08 ` Nadav Amit 2017-08-02 0:08 ` [PATCH v6 2/7] mm: migrate: fix barriers around tlb_flush_pending Nadav Amit 2017-08-02 0:08 ` Nadav Amit 2017-08-02 0:08 ` Nadav Amit [this message] 2017-08-02 0:08 ` [PATCH v6 3/7] Revert "mm: numa: defer TLB flush for THP migration as long as possible" Nadav Amit 2017-08-11 10:50 ` Peter Zijlstra 2017-08-11 10:50 ` Peter Zijlstra 2017-08-02 0:08 ` [PATCH v6 4/7] mm: refactoring TLB gathering API Nadav Amit 2017-08-02 0:08 ` Nadav Amit 2017-08-02 0:08 ` Nadav Amit 2017-08-11 9:23 ` Peter Zijlstra 2017-08-11 9:23 ` Peter Zijlstra 2017-08-11 17:12 ` Nadav Amit 2017-08-11 17:12 ` Nadav Amit 2017-08-14 0:49 ` Minchan Kim 2017-08-14 0:49 ` Minchan Kim 2017-08-02 0:08 ` [PATCH v6 5/7] mm: make tlb_flush_pending global Nadav Amit 2017-08-02 0:08 ` Nadav Amit 2017-08-02 14:28 ` kbuild test robot 2017-08-02 14:28 ` kbuild test robot 2017-08-02 23:23 ` Minchan Kim 2017-08-02 23:23 ` Minchan Kim 2017-08-02 23:27 ` Andrew Morton 2017-08-02 23:27 ` Andrew Morton 2017-08-02 23:34 ` Minchan Kim 2017-08-02 23:34 ` Minchan Kim 2017-08-03 16:40 ` kbuild test robot 2017-08-03 16:40 ` kbuild test robot 2017-08-02 0:08 ` [PATCH v6 6/7] mm: fix MADV_[FREE|DONTNEED] TLB flush miss problem Nadav Amit 2017-08-02 0:08 ` Nadav Amit 2017-08-02 0:08 ` Nadav Amit 2017-08-08 1:19 ` [lkp-robot] [mm] 7674270022: will-it-scale.per_process_ops -19.3% regression kernel test robot 2017-08-08 1:19 ` kernel test robot 2017-08-08 1:19 ` kernel test robot 2017-08-08 1:19 ` kernel test robot 2017-08-08 2:28 ` Minchan Kim 2017-08-08 2:28 ` Minchan Kim 2017-08-08 2:28 ` Minchan Kim 2017-08-08 4:23 ` Nadav Amit 2017-08-08 4:23 ` Nadav Amit 2017-08-08 4:23 ` Nadav Amit 2017-08-08 5:51 ` Nadav Amit 2017-08-08 5:51 ` Nadav Amit 2017-08-08 5:51 ` Nadav Amit 2017-08-08 8:08 ` Minchan Kim 2017-08-08 8:08 ` Minchan Kim 2017-08-08 8:08 ` Minchan Kim 2017-08-08 8:08 ` Minchan Kim 2017-08-08 8:08 ` Minchan Kim 2017-08-08 8:16 ` Nadav Amit 2017-08-08 8:16 ` Nadav Amit 2017-08-09 1:25 ` Ye Xiaolong 2017-08-09 1:25 ` Ye Xiaolong 2017-08-09 1:25 ` Ye Xiaolong 2017-08-09 1:25 ` Ye Xiaolong 2017-08-09 2:59 ` Ye Xiaolong 2017-08-09 2:59 ` Ye Xiaolong 2017-08-09 2:59 ` Ye Xiaolong 2017-08-09 2:59 ` Ye Xiaolong 2017-08-09 2:59 ` Ye Xiaolong 2017-08-10 4:13 ` Minchan Kim 2017-08-10 4:13 ` Minchan Kim 2017-08-10 4:13 ` Minchan Kim 2017-08-10 4:14 ` Nadav Amit 2017-08-10 4:14 ` Nadav Amit 2017-08-10 4:14 ` Nadav Amit 2017-08-10 4:20 ` Minchan Kim 2017-08-10 4:20 ` Minchan Kim 2017-08-10 4:20 ` Minchan Kim 2017-08-11 13:30 ` [PATCH v6 6/7] mm: fix MADV_[FREE|DONTNEED] TLB flush miss problem Peter Zijlstra 2017-08-11 13:30 ` Peter Zijlstra 2017-08-13 6:14 ` Nadav Amit 2017-08-13 12:08 ` Peter Zijlstra 2017-08-13 12:08 ` Peter Zijlstra 2017-08-13 12:08 ` Peter Zijlstra 2017-08-14 1:26 ` Minchan Kim 2017-08-14 1:26 ` Minchan Kim 2017-08-14 1:26 ` Minchan Kim 2017-08-02 0:08 ` [PATCH v6 7/7] mm: fix KSM data corruption Nadav Amit 2017-08-02 0:08 ` Nadav Amit 2017-08-02 23:26 ` [PATCH v6 0/7] fixes of TLB batching races Minchan Kim 2017-08-02 23:26 ` Minchan Kim
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