Re: [RFC 2/2] io_uring: report pinned memory usage

[Jens Axboe <axboe@kernel.dk>]

On 6/11/20 8:23 PM, Bijan Mottahedeh wrote:
> Long term, it makes sense to separate reporting and enforcing of pinned
> memory usage.
> 
> Signed-off-by: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
> 
> It is useful to view
> ---
>  fs/io_uring.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 4248726..cf3acaa 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -7080,6 +7080,8 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
>  static void io_unaccount_mem(struct user_struct *user, unsigned long nr_pages)
>  {
>  	atomic_long_sub(nr_pages, &user->locked_vm);
> +	if (current->mm)
> +		atomic_long_sub(nr_pages, &current->mm->pinned_vm);
>  }
>  
>  static int io_account_mem(struct user_struct *user, unsigned long nr_pages)
> @@ -7096,6 +7098,8 @@ static int io_account_mem(struct user_struct *user, unsigned long nr_pages)
>  			return -ENOMEM;
>  	} while (atomic_long_cmpxchg(&user->locked_vm, cur_pages,
>  					new_pages) != cur_pages);
> +	if (current->mm)
> +		atomic_long_add(nr_pages, &current->mm->pinned_vm);
>  
>  	return 0;
>  }

current->mm should always be valid for these, so I think you can skip the
checking of that and just make it unconditional.

-- 
Jens Axboe