Subject: Re: [RFC PATCH v2 14/22] devlink: implement DEVLINK_CMD_REGION_NEW

From: Jiri Pirko <[email-masked]>
Date: Mon, 2 Mar 2020 18:41:06 +0100

Sat, Feb 15, 2020 at 12:22:13AM CET, [email-masked] wrote:
>Implement support for the DEVLINK_CMD_REGION_NEW command for creating
>snapshots. This new command parallels the existing
>DEVLINK_CMD_REGION_DEL.
>
>In order for DEVLINK_CMD_REGION_NEW to work for a region, the new
>".snapshot" operation must be implemented in the region's ops structure.
>
>The desired snapshot id may be provided. If the requested id is already
>in use, an error will be reported. If no id is provided one will be
>selected in the same way as a triggered snapshot.
>
>In either case, the reference count for that id will be incremented
>in the snapshot IDR.
>
>Signed-off-by: Jacob Keller <[email-masked]>
>---
> .../networking/devlink/devlink-region.rst     | 12 +++-
> include/net/devlink.h                         |  6 ++
> net/core/devlink.c                            | 72 +++++++++++++++++++
> 3 files changed, 88 insertions(+), 2 deletions(-)
>
>diff --git a/Documentation/networking/devlink/devlink-region.rst b/Documentation/networking/devlink/devlink-region.rst
>index 1a7683e7acb2..a24faf2b6b7a 100644
>--- a/Documentation/networking/devlink/devlink-region.rst
>+++ b/Documentation/networking/devlink/devlink-region.rst
>@@ -20,6 +20,11 @@ address regions that are otherwise inaccessible to the user.
> Regions may also be used to provide an additional way to debug complex error
> states, but see also :doc:`devlink-health`
> 
>+Regions may optionally support capturing a snapshot on demand via the
>+``DEVLINK_CMD_REGION_NEW`` netlink message. A driver wishing to allow
>+requested snapshots must implement the ``.snapshot`` callback for the region
>+in its ``devlink_region_ops`` structure.
>+
> example usage
> -------------
> 
>@@ -40,8 +45,11 @@ example usage
>     # Delete a snapshot using:
>     $ devlink region del pci/0000:00:05.0/cr-space snapshot 1
> 
>-    # Trigger (request) a snapshot be taken:
>-    $ devlink region trigger pci/0000:00:05.0/cr-space

Odd. It is actually "devlink region dump". There is no trigger.

>+    # Request an immediate snapshot, if supported by the region
>+    $ devlink region new pci/0000:00:05.0/cr-space

Without ID? I would personally require snapshot id always. Without it,
it looks like you are creating region.

>+
>+    # Request an immediate snapshot with a specific id
>+    $ devlink region new pci/0000:00:05.0/cr-space snapshot 5
> 
>     # Dump a snapshot:
>     $ devlink region dump pci/0000:00:05.0/fw-health snapshot 1
>diff --git a/include/net/devlink.h b/include/net/devlink.h
>index 3a5ff6bea143..3cd0ff2040b2 100644
>--- a/include/net/devlink.h
>+++ b/include/net/devlink.h
>@@ -498,10 +498,16 @@ struct devlink_info_req;
>  * struct devlink_region_ops - Region operations
>  * @name: region name
>  * @destructor: callback used to free snapshot memory when deleting
>+ * @snapshot: callback to request an immediate snapshot. On success,
>+ *            the data variable must be updated to point to the snapshot data.
>+ *            The function will be called while the devlink instance lock is
>+ *            held.
>  */
> struct devlink_region_ops {
> 	const char *name;
> 	void (*destructor)(const void *data);
>+	int (*snapshot)(struct devlink *devlink, struct netlink_ext_ack *extack,
>+			u8 **data);

Please have the same type here and for destructor. "u8 *" I guess.

> };
> 
> struct devlink_fmsg;
>diff --git a/net/core/devlink.c b/net/core/devlink.c
>index 9571063846cc..b5d1b21e5178 100644
>--- a/net/core/devlink.c
>+++ b/net/core/devlink.c
>@@ -4045,6 +4045,71 @@ static int devlink_nl_cmd_region_del(struct sk_buff *skb,
> 	return 0;
> }
> 
>+static int
>+devlink_nl_cmd_region_new(struct sk_buff *skb, struct genl_info *info)
>+{
>+	struct devlink *devlink = info->user_ptr[0];
>+	struct devlink_region *region;
>+	const char *region_name;
>+	u32 snapshot_id;
>+	u8 *data;
>+	int err;
>+
>+	if (!info->attrs[DEVLINK_ATTR_REGION_NAME]) {
>+		NL_SET_ERR_MSG_MOD(info->extack, "No region name provided");
>+		return -EINVAL;
>+	}
>+
>+	region_name = nla_data(info->attrs[DEVLINK_ATTR_REGION_NAME]);
>+	region = devlink_region_get_by_name(devlink, region_name);
>+	if (!region) {
>+		NL_SET_ERR_MSG_MOD(info->extack,

In devlink.c, please don't wrap here.

>+				   "The requested region does not exist");
>+		return -EINVAL;
>+	}
>+
>+	if (!region->ops->snapshot) {
>+		NL_SET_ERR_MSG_MOD(info->extack,
>+				   "The requested region does not support taking an immediate snapshot");
>+		return -EOPNOTSUPP;
>+	}
>+
>+	if (region->cur_snapshots == region->max_snapshots) {
>+		NL_SET_ERR_MSG_MOD(info->extack,
>+				   "The region has reached the maximum number of stored snapshots");
>+		return -ENOMEM;
>+	}
>+
>+	if (info->attrs[DEVLINK_ATTR_REGION_SNAPSHOT_ID]) {
>+		/* __devlink_region_snapshot_create will take care of
>+		 * inserting the snapshot id into the IDR if necessary.
>+		 */
>+		snapshot_id = nla_get_u32(info->attrs[DEVLINK_ATTR_REGION_SNAPSHOT_ID]);
>+
>+		if (devlink_region_snapshot_get_by_id(region, snapshot_id)) {
>+			NL_SET_ERR_MSG_MOD(info->extack,
>+					   "The requested snapshot id is already in use");
>+			return -EEXIST;
>+		}
>+	} else {
>+		snapshot_id = __devlink_region_snapshot_id_get(devlink);
>+	}
>+
>+	err = region->ops->snapshot(devlink, info->extack, &data);

Don't you put the "id"? Looks like a leak.

>+	if (err)
>+		return err;
>+
>+	err = __devlink_region_snapshot_create(region, data, snapshot_id);
>+	if (err)
>+		goto err_free_snapshot_data;
>+
>+	return 0;
>+
>+err_free_snapshot_data:
>+	region->ops->destructor(data);
>+	return err;
>+}
>+
> static int devlink_nl_cmd_region_read_chunk_fill(struct sk_buff *msg,
> 						 struct devlink *devlink,
> 						 u8 *chunk, u32 chunk_size,
>@@ -6358,6 +6423,13 @@ static const struct genl_ops devlink_nl_ops[] = {
> 		.flags = GENL_ADMIN_PERM,
> 		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
> 	},
>+	{
>+		.cmd = DEVLINK_CMD_REGION_NEW,
>+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
>+		.doit = devlink_nl_cmd_region_new,
>+		.flags = GENL_ADMIN_PERM,
>+		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
>+	},
> 	{
> 		.cmd = DEVLINK_CMD_REGION_DEL,
> 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
>-- 
>2.25.0.368.g28a2d05eebfb
>