Re: [RFC PATCH 03/19] drivers/vdpa: Convert vdpa to use the new vm_structure

[Jason Gunthorpe]

On Tue, Jan 24, 2023 at 04:42:32PM +1100, Alistair Popple wrote:
> @@ -990,8 +989,8 @@ static int vduse_dev_reg_umem(struct vduse_dev *dev,
>  
>  	mmap_read_lock(current->mm);
>  
> -	lock_limit = PFN_DOWN(rlimit(RLIMIT_MEMLOCK));
> -	if (npages + atomic64_read(&current->mm->pinned_vm) > lock_limit)
> +	vm_account_init_current(&umem->vm_account);
> +	if (vm_account_pinned(&umem->vm_account, npages))
>  		goto out;
>  
>  	pinned = pin_user_pages(uaddr, npages, FOLL_LONGTERM | FOLL_WRITE,
> @@ -1006,22 +1005,21 @@ static int vduse_dev_reg_umem(struct vduse_dev *dev,
>  	if (ret)
>  		goto out;
>  
> -	atomic64_add(npages, &current->mm->pinned_vm);

Mention in the commit message that this fixes a bug where vdpa would
race the update of mm->pinned_vm and might go past the limit.

Jason