Re: [PATCH 05/21] userfaultfd: add vm_userfaultfd_ctx to the vm_area_struct

[Pavel Emelyanov <xemul@parallels.com>]

> diff --git a/kernel/fork.c b/kernel/fork.c
> index cf65139..cb215c0 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -425,6 +425,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
>  			goto fail_nomem_anon_vma_fork;
>  		tmp->vm_flags &= ~VM_LOCKED;
>  		tmp->vm_next = tmp->vm_prev = NULL;
> +		tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;

This creates an interesting effect when the userfaultfd is used outside of
the process which created and activated one. If I try to monitor the memory
usage of one task with another, once the first task fork()-s, its child
begins to see zero-pages in the places where the monitor task was supposed
to insert pages with data.

>  		file = tmp->vm_file;
>  		if (file) {
>  			struct inode *inode = file_inode(file);
> .
> 

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>