On 07/24, Song Liu wrote:
>
> lock_page(old_page);
> @@ -177,15 +180,24 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
> mmu_notifier_invalidate_range_start(&range);
> err = -EAGAIN;
> if (!page_vma_mapped_walk(&pvmw)) {
> - mem_cgroup_cancel_charge(new_page, memcg, false);
> + if (!orig)
> + mem_cgroup_cancel_charge(new_page, memcg, false);
> goto unlock;
> }
> VM_BUG_ON_PAGE(addr != pvmw.address, old_page);
>
> get_page(new_page);
> - page_add_new_anon_rmap(new_page, vma, addr, false);
> - mem_cgroup_commit_charge(new_page, memcg, false, false);
> - lru_cache_add_active_or_unevictable(new_page, vma);
> + if (orig) {
> + lock_page(new_page); /* for page_add_file_rmap() */
> + page_add_file_rmap(new_page, false);
Shouldn't we re-check new_page->mapping after lock_page() ? Or we can't
race with truncate?
and I am worried this code can try to lock the same page twice...
Say, the probed application does MADV_DONTNEED and then writes "int3"
into vma->vm_file at the same address to fool verify_opcode().
Oleg.
