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    Subject[PATCH 19/29] netvm: skb processing
    In order to make sure emergency packets receive all memory needed to proceed
    ensure processing of emergency skbs happens under PF_MEMALLOC.

    Use the (new) sk_backlog_rcv() wrapper to ensure this for backlog processing.

    Skip taps, since those are user-space again.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    include/net/sock.h | 4 ++++
    net/core/dev.c | 42 +++++++++++++++++++++++++++++++++++++-----
    net/core/sock.c | 19 +++++++++++++++++++
    3 files changed, 60 insertions(+), 5 deletions(-)

    Index: linux-2.6-git/net/core/dev.c
    ===================================================================
    --- linux-2.6-git.orig/net/core/dev.c 2007-02-14 12:16:03.000000000 +0100
    +++ linux-2.6-git/net/core/dev.c 2007-02-14 12:28:33.000000000 +0100
    @@ -1767,10 +1767,23 @@ int netif_receive_skb(struct sk_buff *sk
    struct net_device *orig_dev;
    int ret = NET_RX_DROP;
    __be16 type;
    + unsigned long pflags = current->flags;
    +
    + /* Emergency skb are special, they should
    + * - be delivered to SOCK_VMIO sockets only
    + * - stay away from userspace
    + * - have bounded memory usage
    + *
    + * Use PF_MEMALLOC as a poor mans memory pool - the grouping kind.
    + * This saves us from propagating the allocation context down to all
    + * allocation sites.
    + */
    + if (skb_emergency(skb))
    + current->flags |= PF_MEMALLOC;

    /* if we've gotten here through NAPI, check netpoll */
    if (skb->dev->poll && netpoll_rx(skb))
    - return NET_RX_DROP;
    + goto out;

    if (!skb->tstamp.off_sec)
    net_timestamp(skb);
    @@ -1781,7 +1794,7 @@ int netif_receive_skb(struct sk_buff *sk
    orig_dev = skb_bond(skb);

    if (!orig_dev)
    - return NET_RX_DROP;
    + goto out;

    __get_cpu_var(netdev_rx_stat).total++;

    @@ -1799,6 +1812,9 @@ int netif_receive_skb(struct sk_buff *sk
    }
    #endif

    + if (skb_emergency(skb))
    + goto skip_taps;
    +
    list_for_each_entry_rcu(ptype, &ptype_all, list) {
    if (!ptype->dev || ptype->dev == skb->dev) {
    if (pt_prev)
    @@ -1807,6 +1823,7 @@ int netif_receive_skb(struct sk_buff *sk
    }
    }

    +skip_taps:
    #ifdef CONFIG_NET_CLS_ACT
    if (pt_prev) {
    ret = deliver_skb(skb, pt_prev, orig_dev);
    @@ -1819,15 +1836,27 @@ int netif_receive_skb(struct sk_buff *sk

    if (ret == TC_ACT_SHOT || (ret == TC_ACT_STOLEN)) {
    kfree_skb(skb);
    - goto out;
    + goto unlock;
    }

    skb->tc_verd = 0;
    ncls:
    #endif

    + if (skb_emergency(skb))
    + switch(skb->protocol) {
    + case __constant_htons(ETH_P_ARP):
    + case __constant_htons(ETH_P_IP):
    + case __constant_htons(ETH_P_IPV6):
    + case __constant_htons(ETH_P_8021Q):
    + break;
    +
    + default:
    + goto drop;
    + }
    +
    if (handle_bridge(&skb, &pt_prev, &ret, orig_dev))
    - goto out;
    + goto unlock;

    type = skb->protocol;
    list_for_each_entry_rcu(ptype, &ptype_base[ntohs(type)&15], list) {
    @@ -1842,6 +1871,7 @@ ncls:
    if (pt_prev) {
    ret = pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
    } else {
    +drop:
    kfree_skb(skb);
    /* Jamal, now you will not able to escape explaining
    * me how you were going to use this. :-)
    @@ -1849,8 +1879,10 @@ ncls:
    ret = NET_RX_DROP;
    }

    -out:
    +unlock:
    rcu_read_unlock();
    +out:
    + current->flags = pflags;
    return ret;
    }

    Index: linux-2.6-git/include/net/sock.h
    ===================================================================
    --- linux-2.6-git.orig/include/net/sock.h 2007-02-14 12:32:03.000000000 +0100
    +++ linux-2.6-git/include/net/sock.h 2007-02-14 12:32:37.000000000 +0100
    @@ -510,10 +510,14 @@ static inline void sk_add_backlog(struct
    skb->next = NULL;
    }

    +#ifndef CONFIG_NETVM
    static inline int sk_backlog_rcv(struct sock *sk, struct sk_buff *skb)
    {
    return sk->sk_backlog_rcv(sk, skb);
    }
    +#else
    +extern int sk_backlog_rcv(struct sock *sk, struct sk_buff *skb);
    +#endif

    #define sk_wait_event(__sk, __timeo, __condition) \
    ({ int rc; \
    Index: linux-2.6-git/net/core/sock.c
    ===================================================================
    --- linux-2.6-git.orig/net/core/sock.c 2007-02-14 12:32:07.000000000 +0100
    +++ linux-2.6-git/net/core/sock.c 2007-02-14 12:37:11.000000000 +0100
    @@ -332,6 +332,25 @@ int sk_clear_vmio(struct sock *sk)
    }
    EXPORT_SYMBOL_GPL(sk_clear_vmio);

    +#ifdef CONFIG_NETVM
    +int sk_backlog_rcv(struct sock *sk, struct sk_buff *skb)
    +{
    + if (skb_emergency(skb)) {
    + int ret;
    + unsigned long pflags = current->flags;
    + /* these should have been dropped before queueing */
    + BUG_ON(!sk_has_vmio(sk));
    + current->flags |= PF_MEMALLOC;
    + ret = sk->sk_backlog_rcv(sk, skb);
    + current->flags = pflags;
    + return ret;
    + }
    +
    + return sk->sk_backlog_rcv(sk, skb);
    +}
    +EXPORT_SYMBOL(sk_backlog_rcv);
    +#endif
    +
    static int sock_set_timeout(long *timeo_p, char __user *optval, int optlen)
    {
    struct timeval tv;
    --

    -
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