Commit 3592806c authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
Browse files

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 <sys/mman.h>
  #include <stdio.h>
  #include <unistd.h>

  #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: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: default avatarAndrey Vagin <avagin@openvz.org>
Tested-by: default avatarAndrey Vagin <avagin@openvz.org>
Reviewed-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3e1e4a5f
......@@ -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:
......
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