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mptcp: try harder to borrow memory from subflow under pressure

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If the host is under sever memory pressure, and RX forward
memory allocation for the msk fails, we try to borrow the
required memory from the ingress subflow.

The current attempt is a bit flaky: if skb->truesize is less
than SK_MEM_QUANTUM, the ssk will not release any memory, and
the next schedule will fail again.

Instead, directly move the required amount of pages from the
ssk to the msk, if available

Fixes: 9c3f94e168 ("mptcp: add missing memory scheduling in the rx path")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2021-06-10 15:59:40 -07:00 committed by David S. Miller
parent 22488e4550
commit 72f961320d
1 changed files with 6 additions and 4 deletions
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10
net/mptcp/protocol.c
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@ -280,11 +280,13 @@ static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
/* try to fetch required memory from subflow */
if (!sk_rmem_schedule(sk, skb, skb->truesize)) {
if (ssk->sk_forward_alloc < skb->truesize)
goto drop;
__sk_mem_reclaim(ssk, skb->truesize);
if (!sk_rmem_schedule(sk, skb, skb->truesize))
int amount = sk_mem_pages(skb->truesize) << SK_MEM_QUANTUM_SHIFT;
if (ssk->sk_forward_alloc < amount)
goto drop;
ssk->sk_forward_alloc -= amount;
sk->sk_forward_alloc += amount;
}
/* the skb map_seq accounts for the skb offset: