Cong Wang <xiyou.wangc...@gmail.com> :
[...]
> If you can justify API is not broken by doing that, I am more than happy
> to do it, as I already stated in the latter patch:
>
> "Of course, the logic itself is suspicious, other sendmsg()
> could handle skb allocation failure very well, not sure
> why ATM has to wait for a successful one here. But probably
> it is too late to change since the errno and behavior is
> visible to user-space. So just leave the logic as it is."
>
> For some reason, no one reads that patch. :-/
Believe it or not but I actually read it.
It changes the logic : the original code would have been unable to
escape the while loop on memory failure. Fine, I don't mind the change.
Actually I believe that these two patches are too shy (and backport
unefficient). Instead of trying to reformulate why, here's what I have
in mind. Uncompiled, caveat emptor, etc.
I'll do a (slow) build and test on saturday's night with a pair of
iphase 5575.
diff --git a/net/atm/common.c b/net/atm/common.c
index a3ca922..67f76f3 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -62,21 +62,16 @@ static void vcc_remove_socket(struct sock *sk)
write_unlock_irq(&vcc_sklist_lock);
}
-static struct sk_buff *alloc_tx(struct atm_vcc *vcc, unsigned int size)
+static bool vcc_tx_ready(struct atm_vcc *vcc, unsigned int size)
{
- struct sk_buff *skb;
struct sock *sk = sk_atm(vcc);
if (sk_wmem_alloc_get(sk) && !atm_may_send(vcc, size)) {
pr_debug("Sorry: wmem_alloc = %d, size = %d, sndbuf = %d\n",
sk_wmem_alloc_get(sk), size, sk->sk_sndbuf);
- return NULL;
+ return false;
}
- while (!(skb = alloc_skb(size, GFP_KERNEL)))
- schedule();
- pr_debug("%d += %d\n", sk_wmem_alloc_get(sk), skb->truesize);
- atomic_add(skb->truesize, &sk->sk_wmem_alloc);
- return skb;
+ return true;
}
static void vcc_sock_destruct(struct sock *sk)
@@ -606,7 +601,7 @@ int vcc_sendmsg(struct socket *sock, struct msghdr *m,
size_t size)
eff = (size+3) & ~3; /* align to word boundary */
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
error = 0;
- while (!(skb = alloc_tx(vcc, eff))) {
+ while (!vcc_tx_ready(vcc, eff)) {
if (m->msg_flags & MSG_DONTWAIT) {
error = -EAGAIN;
break;
@@ -628,6 +623,13 @@ int vcc_sendmsg(struct socket *sock, struct msghdr *m,
size_t size)
finish_wait(sk_sleep(sk), &wait);
if (error)
goto out;
+
+ skb = alloc_skb(eff, GFP_KERNEL);
+ if (!skb)
+ goto out;
+ pr_debug("%d += %d\n", sk_wmem_alloc_get(sk), skb->truesize);
+ atomic_add(skb->truesize, &sk->sk_wmem_alloc);
+
skb->dev = NULL; /* for paths shared with net_device interfaces */
ATM_SKB(skb)->atm_options = vcc->atm_options;
if (!copy_from_iter_full(skb_put(skb, size), size, &m->msg_iter)) {
--
Ueimor
