From 3592806cfa08b7cca968f793c33f8e9460bab395 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Thu, 12 Dec 2013 17:12:33 -0800 Subject: [PATCH] thp: move preallocated PTE page table on move_huge_pmd() Andrey Wagin reported crash on VM_BUG_ON() in pgtable_pmd_page_dtor() with fallowing backtrace: free_pgd_range+0x2bf/0x410 free_pgtables+0xce/0x120 unmap_region+0xe0/0x120 do_munmap+0x249/0x360 move_vma+0x144/0x270 SyS_mremap+0x3b9/0x510 system_call_fastpath+0x16/0x1b The crash can be reproduce with this test case: #define _GNU_SOURCE #include #include #include #define MB (1024 * 1024UL) #define GB (1024 * MB) int main(int argc, char **argv) { char *p; int i; p = mmap((void *) GB, 10 * MB, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0); for (i = 0; i < 10 * MB; i += 4096) p[i] = 1; mremap(p, 10 * MB, 10 * MB, MREMAP_FIXED | MREMAP_MAYMOVE, 2 * GB); return 0; } Due to split PMD lock, we now store preallocated PTE tables for THP pages per-PMD table. It means we need to move them to other PMD table if huge PMD moved there. Signed-off-by: Kirill A. Shutemov Reported-by: Andrey Vagin Tested-by: Andrey Vagin Reviewed-by: Naoya Horiguchi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/huge_memory.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index bccd5a628ea6..33a5dc492810 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1481,8 +1481,18 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); VM_BUG_ON(!pmd_none(*new_pmd)); set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); - if (new_ptl != old_ptl) + if (new_ptl != old_ptl) { + pgtable_t pgtable; + + /* + * Move preallocated PTE page table if new_pmd is on + * different PMD page table. + */ + pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); + pgtable_trans_huge_deposit(mm, new_pmd, pgtable); + spin_unlock(new_ptl); + } spin_unlock(old_ptl); } out: -- 2.20.1