From 9818b8cde6221fe7a52aad816425f67d4439b14e Mon Sep 17 00:00:00 2001 From: Huang Ying Date: Thu, 14 Jul 2016 12:07:12 -0700 Subject: madvise_free, thp: fix madvise_free_huge_pmd return value after splitting madvise_free_huge_pmd should return 0 if the fallback PTE operations are required. In madvise_free_huge_pmd, if part pages of THP are discarded, the THP will be split and fallback PTE operations should be used if splitting succeeds. But the original code will make fallback PTE operations skipped, after splitting succeeds. Fix that via make madvise_free_huge_pmd return 0 after splitting successfully, so that the fallback PTE operations will be done. Link: http://lkml.kernel.org/r/1467135452-16688-1-git-send-email-ying.huang@intel.com Signed-off-by: "Huang, Ying" Acked-by: Minchan Kim Cc: "Kirill A. Shutemov" Cc: Vlastimil Babka Cc: Jerome Marchand Cc: Andrea Arcangeli Cc: Ebru Akagunduz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/huge_memory.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) (limited to 'mm/huge_memory.c') diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9ed58530f695..55940d173318 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1624,14 +1624,9 @@ int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, if (next - addr != HPAGE_PMD_SIZE) { get_page(page); spin_unlock(ptl); - if (split_huge_page(page)) { - put_page(page); - unlock_page(page); - goto out_unlocked; - } + split_huge_page(page); put_page(page); unlock_page(page); - ret = 1; goto out_unlocked; } -- cgit v1.2.3-70-g09d2 From 33f4751e99601b7bfd1d66aedabd3ee9140922de Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Thu, 14 Jul 2016 12:07:32 -0700 Subject: mm: thp: move pmd check inside ptl for freeze_page() I found a race condition triggering VM_BUG_ON() in freeze_page(), when running a testcase with 3 processes: - process 1: keep writing thp, - process 2: keep clearing soft-dirty bits from virtual address of process 1 - process 3: call migratepages for process 1, The kernel message is like this: kernel BUG at /src/linux-dev/mm/huge_memory.c:3096! invalid opcode: 0000 [#1] SMP Modules linked in: cfg80211 rfkill crc32c_intel ppdev serio_raw pcspkr virtio_balloon virtio_console parport_pc parport pvpanic acpi_cpufreq tpm_tis tpm i2c_piix4 virtio_blk virtio_net ata_generic pata_acpi floppy virtio_pci virtio_ring virtio CPU: 0 PID: 28863 Comm: migratepages Not tainted 4.6.0-v4.6-160602-0827-+ #2 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 task: ffff880037320000 ti: ffff88007cdd0000 task.ti: ffff88007cdd0000 RIP: 0010:[] [] split_huge_page_to_list+0x496/0x590 RSP: 0018:ffff88007cdd3b70 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffff88007c7b88c0 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000700000200 RDI: ffffea0003188000 RBP: ffff88007cdd3bb8 R08: 0000000000000001 R09: 00003ffffffff000 R10: ffff880000000000 R11: ffffc000001fffff R12: ffffea0003188000 R13: ffffea0003188000 R14: 0000000000000000 R15: 0400000000000080 FS: 00007f8ec241d740(0000) GS:ffff88007dc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8ec1f3ed20 CR3: 000000003707b000 CR4: 00000000000006f0 Call Trace: ? list_del+0xd/0x30 queue_pages_pte_range+0x4d1/0x590 __walk_page_range+0x204/0x4e0 walk_page_range+0x71/0xf0 queue_pages_range+0x75/0x90 ? queue_pages_hugetlb+0x190/0x190 ? new_node_page+0xc0/0xc0 ? change_prot_numa+0x40/0x40 migrate_to_node+0x71/0xd0 do_migrate_pages+0x1c3/0x210 SyS_migrate_pages+0x261/0x290 entry_SYSCALL_64_fastpath+0x1a/0xa4 Code: e8 b0 87 fb ff 0f 0b 48 c7 c6 30 32 9f 81 e8 a2 87 fb ff 0f 0b 48 c7 c6 b8 46 9f 81 e8 94 87 fb ff 0f 0b 85 c0 0f 84 3e fd ff ff <0f> 0b 85 c0 0f 85 a6 00 00 00 48 8b 75 c0 4c 89 f7 41 be f0 ff RIP split_huge_page_to_list+0x496/0x590 I'm not sure of the full scenario of the reproduction, but my debug showed that split_huge_pmd_address(freeze=true) returned without running main code of pmd splitting because pmd_present(*pmd) in precheck somehow returned 0. If this happens, the subsequent try_to_unmap() fails and returns non-zero (because page_mapcount() still > 0), and finally VM_BUG_ON() fires. This patch tries to fix it by prechecking pmd state inside ptl. Link: http://lkml.kernel.org/r/1466990929-7452-1-git-send-email-n-horiguchi@ah.jp.nec.com Signed-off-by: Naoya Horiguchi Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/huge_mm.h | 4 ++-- mm/huge_memory.c | 31 ++++++++++++------------------- 2 files changed, 14 insertions(+), 21 deletions(-) (limited to 'mm/huge_memory.c') diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 419fb9e03447..f0a7a0320300 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -94,7 +94,7 @@ static inline int split_huge_page(struct page *page) void deferred_split_huge_page(struct page *page); void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, - unsigned long address, bool freeze); + unsigned long address, bool freeze, struct page *page); #define split_huge_pmd(__vma, __pmd, __address) \ do { \ @@ -102,7 +102,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, if (pmd_trans_huge(*____pmd) \ || pmd_devmap(*____pmd)) \ __split_huge_pmd(__vma, __pmd, __address, \ - false); \ + false, NULL); \ } while (0) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 55940d173318..343a2b7e57aa 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2984,7 +2984,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, } void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, - unsigned long address, bool freeze) + unsigned long address, bool freeze, struct page *page) { spinlock_t *ptl; struct mm_struct *mm = vma->vm_mm; @@ -2992,8 +2992,17 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE); ptl = pmd_lock(mm, pmd); + + /* + * If caller asks to setup a migration entries, we need a page to check + * pmd against. Otherwise we can end up replacing wrong page. + */ + VM_BUG_ON(freeze && !page); + if (page && page != pmd_page(*pmd)) + goto out; + if (pmd_trans_huge(*pmd)) { - struct page *page = pmd_page(*pmd); + page = pmd_page(*pmd); if (PageMlocked(page)) clear_page_mlock(page); } else if (!pmd_devmap(*pmd)) @@ -3020,24 +3029,8 @@ void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, return; pmd = pmd_offset(pud, address); - if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd))) - return; - /* - * If caller asks to setup a migration entries, we need a page to check - * pmd against. Otherwise we can end up replacing wrong page. - */ - VM_BUG_ON(freeze && !page); - if (page && page != pmd_page(*pmd)) - return; - - /* - * Caller holds the mmap_sem write mode or the anon_vma lock, - * so a huge pmd cannot materialize from under us (khugepaged - * holds both the mmap_sem write mode and the anon_vma lock - * write mode). - */ - __split_huge_pmd(vma, pmd, address, freeze); + __split_huge_pmd(vma, pmd, address, freeze, page); } void vma_adjust_trans_huge(struct vm_area_struct *vma, -- cgit v1.2.3-70-g09d2