Re: [PATCH 2/2] Revert "Bluetooth: RFCOMM: Replace use of memcpy_from_msg with bt_skb_sendmmsg"

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

Hi Paul,

On Tue, Feb 8, 2022 at 2:20 PM Paul Menzel <pmenzel@molgen.mpg.de> wrote:
>
> This reverts commit 81be03e026dc0c16dc1c64e088b2a53b73caa895.
>
> Since the commit, transferring files greater than some bytes to the
> Nokia N9 (MeeGo) or Jolla (Sailfish OS) is not possible anymore.
>
>     # obexctl
>     [NEW] Client /org/bluez/obex
>     [obex]# connect 40:98:4E:5B:CE:XX
>     Attempting to connect to 40:98:4E:5B:CE:XX
>     [NEW] Session /org/bluez/obex/client/session0 [default]
>     [NEW] ObjectPush /org/bluez/obex/client/session0
>     Connection successful
>     [40:98:4E:5B:CE:XX]# send /lib/systemd/systemd
>     Attempting to send /lib/systemd/systemd to /org/bluez/obex/client/session0
>     [NEW] Transfer /org/bluez/obex/client/session0/transfer0
>     Transfer /org/bluez/obex/client/session0/transfer0
>         Status: queued
>         Name: systemd
>         Size: 1841712
>         Filename: /lib/systemd/systemd
>         Session: /org/bluez/obex/client/session0
>     [CHG] Transfer /org/bluez/obex/client/session0/transfer0 Status: active
>     [CHG] Transfer /org/bluez/obex/client/session0/transfer0 Transferred: 32737 (@32KB/s 00:55)
>     [CHG] Transfer /org/bluez/obex/client/session0/transfer0 Status: error
>     [DEL] Transfer /org/bluez/obex/client/session0/transfer0
>
> Reverting it, fixes the regression.
>
> Link: https://lore.kernel.org/linux-bluetooth/aa3ee7ac-6c52-3861-1798-3cc1a37f6ebf@molgen.mpg.de/T/#m1f9673e4ab0d55a7dccf87905337ab2e67d689f1
> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>

We would be much better off with the explanation on why it is causing
a regression on these, is there an error? On top of that we can avoid
such regressions by introducing a test to rfcomm-tester to transfer
big PDUs.

> ---
>  net/bluetooth/rfcomm/core.c | 50 ++++++-------------------------------
>  net/bluetooth/rfcomm/sock.c | 46 ++++++++++++++++++++++++++--------
>  2 files changed, 43 insertions(+), 53 deletions(-)
>
> diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
> index 7324764384b6..f2bacb464ccf 100644
> --- a/net/bluetooth/rfcomm/core.c
> +++ b/net/bluetooth/rfcomm/core.c
> @@ -549,58 +549,22 @@ struct rfcomm_dlc *rfcomm_dlc_exists(bdaddr_t *src, bdaddr_t *dst, u8 channel)
>         return dlc;
>  }
>
> -static int rfcomm_dlc_send_frag(struct rfcomm_dlc *d, struct sk_buff *frag)
> -{
> -       int len = frag->len;
> -
> -       BT_DBG("dlc %p mtu %d len %d", d, d->mtu, len);
> -
> -       if (len > d->mtu)
> -               return -EINVAL;
> -
> -       rfcomm_make_uih(frag, d->addr);
> -       __skb_queue_tail(&d->tx_queue, frag);
> -
> -       return len;
> -}
> -
>  int rfcomm_dlc_send(struct rfcomm_dlc *d, struct sk_buff *skb)
>  {
> -       unsigned long flags;
> -       struct sk_buff *frag, *next;
> -       int len;
> +       int len = skb->len;
>
>         if (d->state != BT_CONNECTED)
>                 return -ENOTCONN;
>
> -       frag = skb_shinfo(skb)->frag_list;
> -       skb_shinfo(skb)->frag_list = NULL;
> -
> -       /* Queue all fragments atomically. */
> -       spin_lock_irqsave(&d->tx_queue.lock, flags);
> -
> -       len = rfcomm_dlc_send_frag(d, skb);
> -       if (len < 0 || !frag)
> -               goto unlock;
> -
> -       for (; frag; frag = next) {
> -               int ret;
> -
> -               next = frag->next;
> -
> -               ret = rfcomm_dlc_send_frag(d, frag);
> -               if (ret < 0) {
> -                       kfree_skb(frag);
> -                       goto unlock;
> -               }
> +       BT_DBG("dlc %p mtu %d len %d", d, d->mtu, len);
>
> -               len += ret;
> -       }
> +       if (len > d->mtu)
> +               return -EINVAL;
>
> -unlock:
> -       spin_unlock_irqrestore(&d->tx_queue.lock, flags);
> +       rfcomm_make_uih(skb, d->addr);
> +       skb_queue_tail(&d->tx_queue, skb);
>
> -       if (len > 0 && !test_bit(RFCOMM_TX_THROTTLED, &d->flags))
> +       if (!test_bit(RFCOMM_TX_THROTTLED, &d->flags))
>                 rfcomm_schedule();
>         return len;
>  }
> diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
> index 5938af3e9936..2c95bb58f901 100644
> --- a/net/bluetooth/rfcomm/sock.c
> +++ b/net/bluetooth/rfcomm/sock.c
> @@ -575,20 +575,46 @@ static int rfcomm_sock_sendmsg(struct socket *sock, struct msghdr *msg,
>         lock_sock(sk);
>
>         sent = bt_sock_wait_ready(sk, msg->msg_flags);
> +       if (sent)
> +               goto done;
>
> -       release_sock(sk);
> +       while (len) {
> +               size_t size = min_t(size_t, len, d->mtu);
> +               int err;
>
> -       if (sent)
> -               return sent;
> +               skb = sock_alloc_send_skb(sk, size + RFCOMM_SKB_RESERVE,
> +                               msg->msg_flags & MSG_DONTWAIT, &err);
> +               if (!skb) {
> +                       if (sent == 0)
> +                               sent = err;
> +                       break;
> +               }
> +               skb_reserve(skb, RFCOMM_SKB_HEAD_RESERVE);
> +
> +               err = memcpy_from_msg(skb_put(skb, size), msg, size);
> +               if (err) {
> +                       kfree_skb(skb);
> +                       if (sent == 0)
> +                               sent = err;
> +                       break;
> +               }
> +
> +               skb->priority = sk->sk_priority;
> +
> +               err = rfcomm_dlc_send(d, skb);
> +               if (err < 0) {
> +                       kfree_skb(skb);
> +                       if (sent == 0)
> +                               sent = err;
> +                       break;
> +               }
>
> -       skb = bt_skb_sendmmsg(sk, msg, len, d->mtu, RFCOMM_SKB_HEAD_RESERVE,
> -                             RFCOMM_SKB_TAIL_RESERVE);
> -       if (IS_ERR_OR_NULL(skb))
> -               return PTR_ERR(skb);
> +               sent += size;
> +               len  -= size;
> +       }
>
> -       sent = rfcomm_dlc_send(d, skb);
> -       if (sent < 0)
> -               kfree_skb(skb);
> +done:
> +       release_sock(sk);
>
>         return sent;
>  }
> --
> 2.34.1
>


-- 
Luiz Augusto von Dentz