@@ -615,7 +615,9 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
* Hide vma from rmap and truncate_pagecache before freeing
* pgtables
*/
+ write_seqcount_begin(&vma->vm_sequence);
unlink_anon_vmas(vma);
+ write_seqcount_end(&vma->vm_sequence);
unlink_file_vma(vma);
if (is_vm_hugetlb_page(vma)) {
@@ -629,7 +631,9 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
&& !is_vm_hugetlb_page(next)) {
vma = next;
next = vma->vm_next;
+ write_seqcount_begin(&vma->vm_sequence);
unlink_anon_vmas(vma);
+ write_seqcount_end(&vma->vm_sequence);
unlink_file_vma(vma);
}
free_pgd_range(tlb, addr, vma->vm_end,
The speculative page fault handler must be protected against anon_vma changes. This is because page_add_new_anon_rmap() is called during the speculative path. In addition, don't try speculative page fault if the VMA don't have an anon_vma structure allocated because its allocation should be protected by the mmap_sem. In __vma_adjust() when importer->anon_vma is set, there is no need to protect against speculative page faults since speculative page fault is aborted if the vma->anon_vma is not set. When calling page_add_new_anon_rmap() vma->anon_vma is necessarily valid since we checked for it when locking the pte and the anon_vma is removed once the pte is unlocked. So even if the speculative page fault handler is running concurrently with do_unmap(), as the pte is locked in unmap_region() - through unmap_vmas() - and the anon_vma unlinked later, because we check for the vma sequence counter which is updated in unmap_page_range() before locking the pte, and then in free_pgtables() so when locking the pte the change will be detected. Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com> --- mm/memory.c | 4 ++++ 1 file changed, 4 insertions(+)