devlink: use kvzalloc() to allocate devlink instance resources

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.

    kernel: hv_netvsc 6045bdaa-c0d1-6045-bdaa-c0d16045bdaa eth0: VF slot 1 added
...
    kernel: kworker/0:0: page allocation failure: order:7, mode:0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null),cpuset=/,mems_allowed=0
    kernel: CPU: 0 PID: 24006 Comm: kworker/0:0 Tainted: G            E     5.4...x86_64 #1
    kernel: Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090008  12/07/2018
    kernel: Workqueue: events work_for_cpu_fn
    kernel: Call Trace:
    kernel: dump_stack+0x8b/0xc8
    kernel: warn_alloc+0xff/0x170
    kernel: __alloc_pages_slowpath+0x92c/0xb2b
    kernel: ? get_page_from_freelist+0x1d4/0x1140
    kernel: __alloc_pages_nodemask+0x2f9/0x320
    kernel: alloc_pages_current+0x6a/0xb0
    kernel: kmalloc_order+0x1e/0x70
    kernel: kmalloc_order_trace+0x26/0xb0
    kernel: ? __switch_to_asm+0x34/0x70
    kernel: __kmalloc+0x276/0x280
    kernel: ? _raw_spin_unlock_irqrestore+0x1e/0x40
    kernel: devlink_alloc+0x29/0x110
    kernel: mlx5_devlink_alloc+0x1a/0x20 [mlx5_core]
    kernel: init_one+0x1d/0x650 [mlx5_core]
    kernel: local_pci_probe+0x46/0x90
    kernel: work_for_cpu_fn+0x1a/0x30
    kernel: process_one_work+0x16d/0x390
    kernel: worker_thread+0x1d3/0x3f0
    kernel: kthread+0x105/0x140
    kernel: ? max_active_store+0x80/0x80
    kernel: ? kthread_bind+0x20/0x20
    kernel: ret_from_fork+0x3a/0x50
Signed-off-by: Jian Wen <wenjian1@xiaomi.com>
Link: https://lore.kernel.org/r/20240327082128.942818-1-wenjian1@xiaomi.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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);