netdev - Re: [net-next v2 10/11] netdevsim: support taking immediate snapshot via devlink

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Date:   Thu, 26 Mar 2020 10:00:27 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jacob Keller <jacob.e.keller@...el.com>
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>
Subject: Re: [net-next v2 10/11] netdevsim: support taking immediate snapshot
 via devlink

Thu, Mar 26, 2020 at 04:51:56AM CET, jacob.e.keller@...el.com wrote:
>Implement the .snapshot region operation for the dummy data region. This
>enables a region snapshot to be taken upon request via the new
>DEVLINK_CMD_REGION_SNAPSHOT command.
>
>Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
>---
> drivers/net/netdevsim/dev.c                   | 30 ++++++++++++++-----
> .../drivers/net/netdevsim/devlink.sh          | 10 +++++++
> 2 files changed, 33 insertions(+), 7 deletions(-)
>
>diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c
>index 53ec891659eb..ffc295c7653e 100644
>--- a/drivers/net/netdevsim/dev.c
>+++ b/drivers/net/netdevsim/dev.c
>@@ -39,24 +39,39 @@ static struct dentry *nsim_dev_ddir;
> 
> #define NSIM_DEV_DUMMY_REGION_SIZE (1024 * 32)
> 
>+static int
>+nsim_dev_take_snapshot(struct devlink *devlink, struct netlink_ext_ack *extack,
>+		       u8 **data)
>+{
>+	void *dummy_data;
>+
>+	dummy_data = kmalloc(NSIM_DEV_DUMMY_REGION_SIZE, GFP_KERNEL);
>+	if (!dummy_data)
>+		return -ENOMEM;
>+
>+	get_random_bytes(dummy_data, NSIM_DEV_DUMMY_REGION_SIZE);
>+
>+	*data = dummy_data;
>+
>+	return 0;
>+}
>+
> static ssize_t nsim_dev_take_snapshot_write(struct file *file,
> 					    const char __user *data,
> 					    size_t count, loff_t *ppos)
> {
> 	struct nsim_dev *nsim_dev = file->private_data;
> 	struct devlink *devlink = priv_to_devlink(nsim_dev);
>-	void *dummy_data;
>+	u8 *dummy_data;
> 	int err;
> 	u32 id;
> 
>-	dummy_data = kmalloc(NSIM_DEV_DUMMY_REGION_SIZE, GFP_KERNEL);
>-	if (!dummy_data)
>-		return -ENOMEM;
>-
>-	get_random_bytes(dummy_data, NSIM_DEV_DUMMY_REGION_SIZE);
>+	err = nsim_dev_take_snapshot(devlink, NULL, &dummy_data);
>+	if (err)
>+		return err;
> 
> 	err = devlink_region_snapshot_id_get(devlink, &id);
>-	if (err)
>+	if (err) {

Hmm, this looks odd. How does the code compile before this patch is
applied?


> 		pr_err("Failed to get snapshot id\n");
> 		return err;
> 	}
>@@ -350,6 +365,7 @@ static void nsim_devlink_param_load_driverinit_values(struct devlink *devlink)
> static const struct devlink_region_ops dummy_region_ops = {
> 	.name = "dummy",
> 	.destructor = &kfree,
>+	.snapshot = nsim_dev_take_snapshot,
> };
> 
> static int nsim_dev_dummy_region_init(struct nsim_dev *nsim_dev,
>diff --git a/tools/testing/selftests/drivers/net/netdevsim/devlink.sh b/tools/testing/selftests/drivers/net/netdevsim/devlink.sh
>index 025a84c2ab5a..32cb2a159c70 100755
>--- a/tools/testing/selftests/drivers/net/netdevsim/devlink.sh
>+++ b/tools/testing/selftests/drivers/net/netdevsim/devlink.sh
>@@ -141,6 +141,16 @@ regions_test()
> 
> 	check_region_snapshot_count dummy post-first-delete 2
> 
>+	devlink region new $DL_HANDLE/dummy snapshot 25
>+	check_err $? "Failed to create a new snapshot with id 25"
>+
>+	check_region_snapshot_count dummy post-first-request 3
>+
>+	devlink region del $DL_HANDLE/dummy snapshot 25
>+	check_err $? "Failed to delete snapshot with id 25"
>+
>+	check_region_snapshot_count dummy post-second-delete 2
>+
> 	log_test "regions test"
> }
> 
>-- 
>2.24.1
>