Message-ID: <909fd3b2-19e8-8c13-6ede-cfd6051c6f1d@amazon.com>
Date:   Fri, 20 Apr 2018 14:52:41 +0200
From:   <staskins@...zon.com>
To:     Juergen Gross <jgross@...e.com>
CC:     <jakub.kicinski@...ronome.com>, <hpa@...or.com>,
        <mcroce@...hat.com>, <tglx@...utronix.de>, <ggarcia@...a.uab.cat>,
        <daniel@...earbox.net>, <x86@...nel.org>, <mingo@...hat.com>,
        <xen-devel@...ts.xenproject.org>, <axboe@...nel.dk>,
        <konrad.wilk@...cle.com>, <amir.jer.levy@...el.com>,
        <paul.durrant@...rix.com>, <stefanha@...hat.com>,
        <dsa@...ulusnetworks.com>, <boris.ostrovsky@...cle.com>,
        <linux-block@...r.kernel.org>, <wei.liu2@...rix.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <davem@...emloft.net>, <dwmw@...zon.co.uk>, <roger.pau@...rix.com>
Subject: Re: [PATCH 2/3] xen netback: add fault injection facility

On 04/20/18 13:25, Juergen Gross wrote:
> On 20/04/18 12:47, Stanislav Kinsburskii wrote:
>> diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
>> index 8918466..5cc9acd 100644
>> --- a/drivers/net/Kconfig
>> +++ b/drivers/net/Kconfig
>> @@ -465,6 +465,14 @@ config XEN_NETDEV_BACKEND
>>   	  compile this driver as a module, chose M here: the module
>>   	  will be called xen-netback.
>>   
>> +config XEN_NETDEV_BACKEND_FAULT_INJECTION
>> +	  bool "Xen net-device backend driver fault injection"
>> +	  depends on XEN_NETDEV_BACKEND
>> +	  depends on XEN_FAULT_INJECTION
>> +	  default n
>> +	  help
>> +	    Allow to inject errors to Xen backend network driver
>> +
>>   config VMXNET3
>>   	tristate "VMware VMXNET3 ethernet driver"
>>   	depends on PCI && INET
>> diff --git a/drivers/net/xen-netback/Makefile b/drivers/net/xen-netback/Makefile
>> index d49798a..28abcdc 100644
>> --- a/drivers/net/xen-netback/Makefile
>> +++ b/drivers/net/xen-netback/Makefile
>> @@ -1,3 +1,4 @@
>>   obj-$(CONFIG_XEN_NETDEV_BACKEND) := xen-netback.o
>>   
>>   xen-netback-y := netback.o xenbus.o interface.o hash.o rx.o
>> +xen-netback-$(CONFIG_XEN_NETDEV_BACKEND_FAULT_INJECTION) += netback_fi.o
>> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
>> index a46a1e9..30d676d 100644
>> --- a/drivers/net/xen-netback/common.h
>> +++ b/drivers/net/xen-netback/common.h
>> @@ -286,6 +286,9 @@ struct xenvif {
>>   
>>   #ifdef CONFIG_DEBUG_FS
>>   	struct dentry *xenvif_dbg_root;
>> +#ifdef CONFIG_XEN_NETDEV_BACKEND_FAULT_INJECTION
>> +	void *fi_info;
>> +#endif
>>   #endif
>>   
>>   	struct xen_netif_ctrl_back_ring ctrl;
>> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
>> index a27daa2..ecc416e 100644
>> --- a/drivers/net/xen-netback/netback.c
>> +++ b/drivers/net/xen-netback/netback.c
>> @@ -33,6 +33,7 @@
>>    */
>>   
>>   #include "common.h"
>> +#include "netback_fi.h"
>>   
>>   #include <linux/kthread.h>
>>   #include <linux/if_vlan.h>
>> @@ -1649,6 +1650,7 @@ static int __init netback_init(void)
>>   			PTR_ERR(xen_netback_dbg_root));
>>   #endif /* CONFIG_DEBUG_FS */
>>   
>> +	(void) xen_netbk_fi_init();
> This is the only usage of xen_netbk_fi_init(). Why don't you make it
> return void from the beginning?

Well, I could do so, of course.
My intention was to treat this as an error. But then it doesn't 
correlate to ignored debugfs directory creation error above.

>>   	return 0;
>>   
>>   failed_init:
>> @@ -1659,6 +1661,7 @@ module_init(netback_init);
>>   
>>   static void __exit netback_fini(void)
>>   {
>> +	xen_netbk_fi_fini();
>>   #ifdef CONFIG_DEBUG_FS
>>   	if (!IS_ERR_OR_NULL(xen_netback_dbg_root))
>>   		debugfs_remove_recursive(xen_netback_dbg_root);
>> diff --git a/drivers/net/xen-netback/netback_fi.c b/drivers/net/xen-netback/netback_fi.c
>> new file mode 100644
>> index 0000000..47541d0
>> --- /dev/null
>> +++ b/drivers/net/xen-netback/netback_fi.c
>> @@ -0,0 +1,119 @@
>> +/*
>> + * Fault injection interface for Xen backend network driver
>> + *
>> + * Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
>> + *
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public License version 2
>> + * as published by the Free Software Foundation; or, when distributed
>> + * separately from the Linux kernel or incorporated into other
>> + * software packages, subject to the following license:
> SPDX again.

Will fix.

>
>> + *
>> + * Permission is hereby granted, free of charge, to any person obtaining a copy
>> + * of this source file (the "Software"), to deal in the Software without
>> + * restriction, including without limitation the rights to use, copy, modify,
>> + * merge, publish, distribute, sublicense, and/or sell copies of the Software,
>> + * and to permit persons to whom the Software is furnished to do so, subject to
>> + * the following conditions:
>> + *
>> + * The above copyright notice and this permission notice shall be included in
>> + * all copies or substantial portions of the Software.
>> + *
>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
>> + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
>> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
>> + * IN THE SOFTWARE.
>> + */
>> +
>> +#include "common.h"
>> +
>> +#include <linux/debugfs.h>
>> +
>> +#include <xen/fault_inject.h>
>> +#include "netback_fi.h"
>> +
>> +static struct dentry *vif_fi_dir;
>> +
>> +static const char *xenvif_fi_names[] = {
>> +};
>> +
>> +struct xenvif_fi {
>> +	struct dentry *dir;
>> +	struct xen_fi *faults[XENVIF_FI_MAX];
>> +};
>> +
>> +int xen_netbk_fi_init(void)
>> +{
>> +	vif_fi_dir = xen_fi_dir_create("xen-netback");
>> +	if (!vif_fi_dir)
>> +		return -ENOMEM;
>> +	return 0;
>> +}
>> +
>> +void xen_netbk_fi_fini(void)
>> +{
>> +	debugfs_remove_recursive(vif_fi_dir);
>> +}
>> +
>> +void xenvif_fi_fini(struct xenvif *vif)
>> +{
>> +	struct xenvif_fi *vfi = vif->fi_info;
>> +	int fi;
>> +
>> +	if (!vif->fi_info)
>> +		return;
>> +
>> +	vif->fi_info = NULL;
>> +
>> +	for (fi = 0; fi < XENVIF_FI_MAX; fi++)
>> +		xen_fi_del(vfi->faults[fi]);
>> +	debugfs_remove_recursive(vfi->dir);
>> +	kfree(vfi);
>> +}
>> +
>> +int xenvif_fi_init(struct xenvif *vif)
>> +{
>> +	struct dentry *parent;
>> +	struct xenvif_fi *vfi;
>> +	int fi, err = -ENOMEM;
>> +
>> +	parent = vif_fi_dir;
>> +	if (!parent)
>> +		return -ENOMEM;
>> +
>> +	vfi = kmalloc(sizeof(*vfi), GFP_KERNEL);
>> +	if (!vfi)
>> +		return -ENOMEM;
>> +
>> +	vfi->dir = debugfs_create_dir(vif->dev->name, parent);
>> +	if (!vfi->dir)
>> +		goto err_dir;
>> +
>> +	for (fi = 0; fi < XENVIF_FI_MAX; fi++) {
>> +		vfi->faults[fi] = xen_fi_dir_add(vfi->dir,
>> +				xenvif_fi_names[fi]);
> How does this work? xenvif_fi_names[] is an empty array and this is the
> only reference to it. Who is allocating the memory for that array?

Well, it works in the way one adds a var to enum (which is used as a key 
later) and a corresponding string into the array (which is used as a 
name for the fault directory in sysfs).

>> +		if (!vfi->faults[fi])
>> +			goto err_fault;
>> +	}
>> +
>> +	vif->fi_info = vfi;
>> +	return 0;
>> +
>> +err_fault:
>> +	for (; fi > 0; fi--)
>> +		xen_fi_del(vfi->faults[fi]);
> What about vfi->faults[0] ?

Thanks! Will fix.


>> +	debugfs_remove_recursive(vfi->dir);
>> +err_dir:
>> +	kfree(vfi);
>> +	return err;
>> +}
>> +
>> +bool xenvif_should_fail(struct xenvif *vif, xenvif_fi_t type)
>> +{
>> +	struct xenvif_fi *vfi = vif->fi_info;
>> +
>> +	return xen_should_fail(vfi->faults[type]);
>> +}
>> diff --git a/drivers/net/xen-netback/netback_fi.h b/drivers/net/xen-netback/netback_fi.h
>> new file mode 100644
>> index 0000000..895c6a6
>> --- /dev/null
>> +++ b/drivers/net/xen-netback/netback_fi.h
>> @@ -0,0 +1,35 @@
>> +#ifndef _XEN_NETBACK_FI_H
>> +#define _XEN_NETBACK_FI_H
>> +
>> +struct xen_fi;
> Why?

Ditto.

>> +
>> +typedef enum {
>> +	XENVIF_FI_MAX
>> +} xenvif_fi_t;
> It would have helped if you had added some users of the stuff you are
> adding here. This enum just looks weird this way.
>
it in pla
Yeah... Probably I should mark this thing as a RFC.

>> +
>> +#ifdef CONFIG_XEN_NETDEV_BACKEND_FAULT_INJECTION
>> +
>> +int xen_netbk_fi_init(void);
>> +void xen_netbk_fi_fini(void);
>> +
>> +void xenvif_fi_fini(struct xenvif *vif);
>> +int xenvif_fi_init(struct xenvif *vif);
>> +
>> +bool xenvif_should_fail(struct xenvif *vif, xenvif_fi_t type);
>> +
>> +#else
>> +
>> +static inline int xen_netbk_fi_init(void) { return 0; }
>> +static inline void xen_netbk_fi_fini(void) { }
>> +
>> +static inline void xenvif_fi_fini(struct xenvif *vif) { }
>> +static inline int xenvif_fi_init(struct xenvif *vif) { return 0; }
>> +
>> +static inline bool xenvif_should_fail(struct xenvif *vif, xenvif_fi_t type)
>> +{
>> +	return false;
>> +}
>> +
>> +#endif /* CONFIG_XEN_NETDEV_BACKEND_FAULT_INJECTION */
>> +
>> +#endif /* _XEN_NETBACK_FI_H */
>> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
>> index e1aef25..c775ee0 100644
>> --- a/drivers/net/xen-netback/xenbus.c
>> +++ b/drivers/net/xen-netback/xenbus.c
>> @@ -21,6 +21,7 @@
>>   #include "common.h"
>>   #include <linux/vmalloc.h>
>>   #include <linux/rtnetlink.h>
>> +#include "netback_fi.h"
>>   
>>   struct backend_info {
>>   	struct xenbus_device *dev;
>> @@ -502,6 +503,7 @@ static void backend_disconnect(struct backend_info *be)
>>   #ifdef CONFIG_DEBUG_FS
>>   		xenvif_debugfs_delif(vif);
>>   #endif /* CONFIG_DEBUG_FS */
>> +		xenvif_fi_fini(vif);
>>   		xenvif_disconnect_data(vif);
>>   
>>   		/* At this point some of the handlers may still be active
>> @@ -1024,6 +1026,10 @@ static void connect(struct backend_info *be)
>>   		}
>>   	}
>>   
>> +	err = xenvif_fi_init(be->vif);
>> +	if (err)
>> +		goto err;
>> +
>>   #ifdef CONFIG_DEBUG_FS
>>   	xenvif_debugfs_addif(be->vif);
>>   #endif /* CONFIG_DEBUG_FS */
>>
> Without any user of that infrastructure I really can't say whether I
> want this.
>

The code we are using this faults for is not yet sent (we have it in plans).
Probably I'll send it once again after this code using it is sent.
Thanks anyway!

> Juergen
>

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