On Mon, 20 Mar 2023 at 21:54, Nuno Gonçalves <nunog@xxxxxxxx> wrote:
>
> The remap of fill and completion rings was frowned upon as they
> control the usage of UMEM which does not support concurrent use.
> At the same time this would disallow the remap of these rings
> into another process.
>
> A possible use case is that the user wants to transfer the socket/
> UMEM ownership to another process (via SYS_pidfd_getfd) and so
> would need to also remap these rings.
>
> This will have no impact on current usages and just relaxes the
> remap limitation.
Acked-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> Signed-off-by: Nuno Gonçalves <nunog@xxxxxxxx>
> ---
> net/xdp/xsk.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 2ac58b282b5eb..e2571ec067526 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -1301,9 +1301,10 @@ static int xsk_mmap(struct file *file, struct socket *sock,
> loff_t offset = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
> unsigned long size = vma->vm_end - vma->vm_start;
> struct xdp_sock *xs = xdp_sk(sock->sk);
> + int state = READ_ONCE(xs->state);
> struct xsk_queue *q = NULL;
>
> - if (READ_ONCE(xs->state) != XSK_READY)
> + if (state != XSK_READY && state != XSK_BOUND)
> return -EBUSY;
>
> if (offset == XDP_PGOFF_RX_RING) {
> @@ -1314,9 +1315,11 @@ static int xsk_mmap(struct file *file, struct socket *sock,
> /* Matches the smp_wmb() in XDP_UMEM_REG */
> smp_rmb();
> if (offset == XDP_UMEM_PGOFF_FILL_RING)
> - q = READ_ONCE(xs->fq_tmp);
> + q = READ_ONCE(state == XSK_READY ? xs->fq_tmp :
> + xs->pool->fq);
> else if (offset == XDP_UMEM_PGOFF_COMPLETION_RING)
> - q = READ_ONCE(xs->cq_tmp);
> + q = READ_ONCE(state == XSK_READY ? xs->cq_tmp :
> + xs->pool->cq);
> }
>
> if (!q)
> --
> 2.40.0
>
