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Revision 6e474083f3daf3a3546737f5d7d502ad12eb257c authored by Wei Xu on 01 December 2017, 10:10:36 UTC, committed by David S. Miller on 03 December 2017, 02:31:03 UTC 
vhost: fix skb leak in handle_rx()
 
Matthew found a roughly 40% tcp throughput regression with commit
c67df11f(vhost_net: try batch dequing from skb array) as discussed
in the following thread:
https://www.mail-archive.com/netdev@vger.kernel.org/msg187936.html

Eventually we figured out that it was a skb leak in handle_rx()
when sending packets to the VM. This usually happens when a guest
can not drain out vq as fast as vhost fills in, afterwards it sets
off the traffic jam and leaks skb(s) which occurs as no headcount
to send on the vq from vhost side.

This can be avoided by making sure we have got enough headcount
before actually consuming a skb from the batched rx array while
transmitting, which is simply done by moving checking the zero
headcount a bit ahead.

Signed-off-by: Wei Xu <wexu@redhat.com>
Reported-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent fa935ca
Raw File
sa1100_cerf.c 
// SPDX-License-Identifier: GPL-2.0
/*
 * drivers/pcmcia/sa1100_cerf.c
 *
 * PCMCIA implementation routines for CerfBoard
 * Based off the Assabet.
 *
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/gpio.h>

#include <mach/hardware.h>
#include <asm/mach-types.h>
#include <asm/irq.h>
#include <mach/cerf.h>
#include "sa1100_generic.h"

#define CERF_SOCKET	1

static int cerf_pcmcia_hw_init(struct soc_pcmcia_socket *skt)
{
	int ret;

	ret = gpio_request_one(CERF_GPIO_CF_RESET, GPIOF_OUT_INIT_LOW, "CF_RESET");
	if (ret)
		return ret;

	skt->stat[SOC_STAT_CD].gpio = CERF_GPIO_CF_CD;
	skt->stat[SOC_STAT_CD].name = "CF_CD";
	skt->stat[SOC_STAT_BVD1].gpio = CERF_GPIO_CF_BVD1;
	skt->stat[SOC_STAT_BVD1].name = "CF_BVD1";
	skt->stat[SOC_STAT_BVD2].gpio = CERF_GPIO_CF_BVD2;
	skt->stat[SOC_STAT_BVD2].name = "CF_BVD2";
	skt->stat[SOC_STAT_RDY].gpio = CERF_GPIO_CF_IRQ;
	skt->stat[SOC_STAT_RDY].name = "CF_IRQ";

	return 0;
}

static void cerf_pcmcia_hw_shutdown(struct soc_pcmcia_socket *skt)
{
	gpio_free(CERF_GPIO_CF_RESET);
}

static int
cerf_pcmcia_configure_socket(struct soc_pcmcia_socket *skt,
			     const socket_state_t *state)
{
	switch (state->Vcc) {
	case 0:
	case 50:
	case 33:
		break;

	default:
		printk(KERN_ERR "%s(): unrecognized Vcc %u\n",
			__func__, state->Vcc);
		return -1;
	}

	gpio_set_value(CERF_GPIO_CF_RESET, !!(state->flags & SS_RESET));

	return 0;
}

static struct pcmcia_low_level cerf_pcmcia_ops = { 
	.owner			= THIS_MODULE,
	.hw_init		= cerf_pcmcia_hw_init,
	.hw_shutdown		= cerf_pcmcia_hw_shutdown,
	.socket_state		= soc_common_cf_socket_state,
	.configure_socket	= cerf_pcmcia_configure_socket,
};

int pcmcia_cerf_init(struct device *dev)
{
	int ret = -ENODEV;

	if (machine_is_cerf())
		ret = sa11xx_drv_pcmcia_probe(dev, &cerf_pcmcia_ops, CERF_SOCKET, 1);

	return ret;
}
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