netdev - Re: [PATCH net-next v2] devlink: use kvzalloc() to allocate devlink instance resources

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Date: Wed, 27 Mar 2024 11:15:08 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Jian Wen <wenjianhn@...il.com>
CC: <jiri@...lanox.com>, <edumazet@...gle.com>, <davem@...emloft.net>, "Jian
 Wen" <wenjian1@...omi.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2] devlink: use kvzalloc() to allocate devlink
 instance resources

From: Jian Wen <wenjianhn@...il.com>
Date: Wed, 27 Mar 2024 16:21:28 +0800

> During live migration of a virtual machine, the SR-IOV VF need to be
> re-registered. It may fail when the memory is badly fragmented.
> 
> The related log is as follows.
> 
> Mar  1 18:54:12  kernel: hv_netvsc 6045bdaa-c0d1-6045-bdaa-c0d16045bdaa eth0: VF slot 1 added
> ...
> Mar  1 18:54:13  kernel: kworker/0:0: page allocation failure: order:7, mode:0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null),cpuset=/,mems_allowed=0
> Mar  1 18:54:13  kernel: CPU: 0 PID: 24006 Comm: kworker/0:0 Tainted: G            E     5.4...x86_64 #1
> Mar  1 18:54:13  kernel: Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090008  12/07/2018
> Mar  1 18:54:13  kernel: Workqueue: events work_for_cpu_fn
> Mar  1 18:54:13  kernel: Call Trace:
> Mar  1 18:54:13  kernel: dump_stack+0x8b/0xc8
> Mar  1 18:54:13  kernel: warn_alloc+0xff/0x170
> Mar  1 18:54:13  kernel: __alloc_pages_slowpath+0x92c/0xb2b
> Mar  1 18:54:13  kernel: ? get_page_from_freelist+0x1d4/0x1140
> Mar  1 18:54:13  kernel: __alloc_pages_nodemask+0x2f9/0x320
> Mar  1 18:54:13  kernel: alloc_pages_current+0x6a/0xb0
> Mar  1 18:54:13  kernel: kmalloc_order+0x1e/0x70
> Mar  1 18:54:13  kernel: kmalloc_order_trace+0x26/0xb0
> Mar  1 18:54:13  kernel: ? __switch_to_asm+0x34/0x70
> Mar  1 18:54:13  kernel: __kmalloc+0x276/0x280
> Mar  1 18:54:13  kernel: ? _raw_spin_unlock_irqrestore+0x1e/0x40
> Mar  1 18:54:13  kernel: devlink_alloc+0x29/0x110
> Mar  1 18:54:13  kernel: mlx5_devlink_alloc+0x1a/0x20 [mlx5_core]
> Mar  1 18:54:13  kernel: init_one+0x1d/0x650 [mlx5_core]
> Mar  1 18:54:13  kernel: local_pci_probe+0x46/0x90
> Mar  1 18:54:13  kernel: work_for_cpu_fn+0x1a/0x30
> Mar  1 18:54:13  kernel: process_one_work+0x16d/0x390
> Mar  1 18:54:13  kernel: worker_thread+0x1d3/0x3f0
> Mar  1 18:54:13  kernel: kthread+0x105/0x140
> Mar  1 18:54:13  kernel: ? max_active_store+0x80/0x80
> Mar  1 18:54:13  kernel: ? kthread_bind+0x20/0x20
> Mar  1 18:54:13  kernel: ret_from_fork+0x3a/0x50
> 
> Changes since v1:
> - Use struct_size(devlink, priv, priv_size) as suggested by Alexander Lobakin
> 
> Signed-off-by: Jian Wen <wenjian1@...omi.com>

Since it actually fixes a bug splat, you may want to send it with prefix
"net" instead of "net-next" and add a "Fixes:" tag here blaming the
first commit which added Devlink instance allocation. Let's see what
others think.

> ---
>  net/devlink/core.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/net/devlink/core.c b/net/devlink/core.c
> index 7f0b093208d7..f49cd83f1955 100644
> --- a/net/devlink/core.c
> +++ b/net/devlink/core.c
> @@ -314,7 +314,7 @@ static void devlink_release(struct work_struct *work)
>  	mutex_destroy(&devlink->lock);
>  	lockdep_unregister_key(&devlink->lock_key);
>  	put_device(devlink->dev);
> -	kfree(devlink);
> +	kvfree(devlink);
>  }
>  
>  void devlink_put(struct devlink *devlink)
> @@ -420,7 +420,7 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops,
>  	if (!devlink_reload_actions_valid(ops))
>  		return NULL;
>  
> -	devlink = kzalloc(sizeof(*devlink) + priv_size, GFP_KERNEL);
> +	devlink = kvzalloc(struct_size(devlink, priv, priv_size), GFP_KERNEL);
>  	if (!devlink)
>  		return NULL;
>  
> @@ -455,7 +455,7 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops,
>  	return devlink;
>  
>  err_xa_alloc:
> -	kfree(devlink);
> +	kvfree(devlink);
>  	return NULL;
>  }
>  EXPORT_SYMBOL_GPL(devlink_alloc_ns);

Thanks,
Olek