Commit b4b9e355 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds

netvm: set PF_MEMALLOC as appropriate during SKB processing

In order to make sure pfmemalloc packets receive all memory needed to
proceed, ensure processing of pfmemalloc SKBs happens under PF_MEMALLOC.
This is limited to a subset of protocols that are expected to be used for
writing to swap.  Taps are not allowed to use PF_MEMALLOC as these are
expected to communicate with userspace processes which could be paged out.

[a.p.zijlstra@chello.nl: Ideas taken from various patches]
[jslaby@suse.cz: Lock imbalance fix]
Signed-off-by: 's avatarMel Gorman <mgorman@suse.de>
Acked-by: 's avatarDavid S. Miller <davem@davemloft.net>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0614002b
......@@ -754,8 +754,13 @@ static inline __must_check int sk_add_backlog(struct sock *sk, struct sk_buff *s
return 0;
}
extern int __sk_backlog_rcv(struct sock *sk, struct sk_buff *skb);
static inline int sk_backlog_rcv(struct sock *sk, struct sk_buff *skb)
{
if (sk_memalloc_socks() && skb_pfmemalloc(skb))
return __sk_backlog_rcv(sk, skb);
return sk->sk_backlog_rcv(sk, skb);
}
......
......@@ -3155,6 +3155,23 @@ void netdev_rx_handler_unregister(struct net_device *dev)
}
EXPORT_SYMBOL_GPL(netdev_rx_handler_unregister);
/*
* Limit the use of PFMEMALLOC reserves to those protocols that implement
* the special handling of PFMEMALLOC skbs.
*/
static bool skb_pfmemalloc_protocol(struct sk_buff *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):
return true;
default:
return false;
}
}
static int __netif_receive_skb(struct sk_buff *skb)
{
struct packet_type *ptype, *pt_prev;
......@@ -3164,14 +3181,27 @@ static int __netif_receive_skb(struct sk_buff *skb)
bool deliver_exact = false;
int ret = NET_RX_DROP;
__be16 type;
unsigned long pflags = current->flags;
net_timestamp_check(!netdev_tstamp_prequeue, skb);
trace_netif_receive_skb(skb);
/*
* PFMEMALLOC skbs are special, they should
* - be delivered to SOCK_MEMALLOC sockets only
* - stay away from userspace
* - have bounded memory usage
*
* Use PF_MEMALLOC as this saves us from propagating the allocation
* context down to all allocation sites.
*/
if (sk_memalloc_socks() && skb_pfmemalloc(skb))
current->flags |= PF_MEMALLOC;
/* if we've gotten here through NAPI, check netpoll */
if (netpoll_receive_skb(skb))
return NET_RX_DROP;
goto out;
orig_dev = skb->dev;
......@@ -3191,7 +3221,7 @@ another_round:
if (skb->protocol == cpu_to_be16(ETH_P_8021Q)) {
skb = vlan_untag(skb);
if (unlikely(!skb))
goto out;
goto unlock;
}
#ifdef CONFIG_NET_CLS_ACT
......@@ -3201,6 +3231,9 @@ another_round:
}
#endif
if (sk_memalloc_socks() && skb_pfmemalloc(skb))
goto skip_taps;
list_for_each_entry_rcu(ptype, &ptype_all, list) {
if (!ptype->dev || ptype->dev == skb->dev) {
if (pt_prev)
......@@ -3209,13 +3242,18 @@ another_round:
}
}
skip_taps:
#ifdef CONFIG_NET_CLS_ACT
skb = handle_ing(skb, &pt_prev, &ret, orig_dev);
if (!skb)
goto out;
goto unlock;
ncls:
#endif
if (sk_memalloc_socks() && skb_pfmemalloc(skb)
&& !skb_pfmemalloc_protocol(skb))
goto drop;
rx_handler = rcu_dereference(skb->dev->rx_handler);
if (vlan_tx_tag_present(skb)) {
if (pt_prev) {
......@@ -3225,7 +3263,7 @@ ncls:
if (vlan_do_receive(&skb, !rx_handler))
goto another_round;
else if (unlikely(!skb))
goto out;
goto unlock;
}
if (rx_handler) {
......@@ -3235,7 +3273,7 @@ ncls:
}
switch (rx_handler(&skb)) {
case RX_HANDLER_CONSUMED:
goto out;
goto unlock;
case RX_HANDLER_ANOTHER:
goto another_round;
case RX_HANDLER_EXACT:
......@@ -3268,6 +3306,7 @@ ncls:
else
ret = pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
} else {
drop:
atomic_long_inc(&skb->dev->rx_dropped);
kfree_skb(skb);
/* Jamal, now you will not able to escape explaining
......@@ -3276,8 +3315,10 @@ ncls:
ret = NET_RX_DROP;
}
out:
unlock:
rcu_read_unlock();
out:
tsk_restore_flags(current, pflags, PF_MEMALLOC);
return ret;
}
......
......@@ -298,6 +298,22 @@ void sk_clear_memalloc(struct sock *sk)
}
EXPORT_SYMBOL_GPL(sk_clear_memalloc);
int __sk_backlog_rcv(struct sock *sk, struct sk_buff *skb)
{
int ret;
unsigned long pflags = current->flags;
/* these should have been dropped before queueing */
BUG_ON(!sock_flag(sk, SOCK_MEMALLOC));
current->flags |= PF_MEMALLOC;
ret = sk->sk_backlog_rcv(sk, skb);
tsk_restore_flags(current, pflags, PF_MEMALLOC);
return ret;
}
EXPORT_SYMBOL(__sk_backlog_rcv);
#if defined(CONFIG_CGROUPS)
#if !defined(CONFIG_NET_CLS_CGROUP)
int net_cls_subsys_id = -1;
......
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