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bpf: sockmap update/simplify memory accounting scheme

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Instead of tracking wmem_queued and sk_mem_charge by incrementing
in the verdict SK_REDIRECT paths and decrementing in the tx work
path use skb_set_owner_w and sock_writeable helpers. This solves
a few issues with the current code. First, in SK_REDIRECT inc on
sk_wmem_queued and sk_mem_charge were being done without the peers
sock lock being held. Under stress this can result in accounting
errors when tx work and/or multiple verdict decisions are working
on the peer psock.

Additionally, this cleans up the code because we can rely on the
default destructor to decrement memory accounting on kfree_skb. Also
this will trigger sk_write_space when space becomes available on
kfree_skb() which wasn't happening before and prevent __sk_free
from being called until all in-flight packets are completed.

Fixes: 174a79ff95 ("bpf: sockmap with sk redirect support")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Fastabend 2017-09-01 11:29:26 -07:00 committed by David S. Miller
parent 250b0f7831
commit 90a9631cf8
1 changed files with 7 additions and 11 deletions
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18
kernel/bpf/sockmap.c
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@ -111,7 +111,7 @@ static int smap_verdict_func(struct smap_psock *psock, struct sk_buff *skb)
static void smap_do_verdict(struct smap_psock *psock, struct sk_buff *skb)
{
struct sock *sock;
struct sock *sk;
int rc;
/* Because we use per cpu values to feed input from sock redirect
@ -123,16 +123,16 @@ static void smap_do_verdict(struct smap_psock *psock, struct sk_buff *skb)
rc = smap_verdict_func(psock, skb);
switch (rc) {
case SK_REDIRECT:
sock = do_sk_redirect_map();
sk = do_sk_redirect_map();
preempt_enable();
if (likely(sock)) {
struct smap_psock *peer = smap_psock_sk(sock);
if (likely(sk)) {
struct smap_psock *peer = smap_psock_sk(sk);
if (likely(peer &&
test_bit(SMAP_TX_RUNNING, &peer->state) &&
sk_stream_memory_free(peer->sock))) {
peer->sock->sk_wmem_queued += skb->truesize;
sk_mem_charge(peer->sock, skb->truesize);
!sock_flag(sk, SOCK_DEAD) &&
sock_writeable(sk))) {
skb_set_owner_w(skb, sk);
skb_queue_tail(&peer->rxqueue, skb);
schedule_work(&peer->tx_work);
break;
@ -282,16 +282,12 @@ start:
/* Hard errors break pipe and stop xmit */
smap_report_sk_error(psock, n ? -n : EPIPE);
clear_bit(SMAP_TX_RUNNING, &psock->state);
sk_mem_uncharge(psock->sock, skb->truesize);
psock->sock->sk_wmem_queued -= skb->truesize;
kfree_skb(skb);
goto out;
}
rem -= n;
off += n;
} while (rem);
sk_mem_uncharge(psock->sock, skb->truesize);
psock->sock->sk_wmem_queued -= skb->truesize;
kfree_skb(skb);
}
out: