Re: [PATCH 03/15] devlink: add operation to take an immediate snapshot

[Jiri Pirko <jiri@resnulli.us>]

Mon, Feb 03, 2020 at 09:19:23AM CET, linyunsheng@huawei.com wrote:
>On 2020/1/31 6:58, Jacob Keller wrote:
>> Add a new devlink command, DEVLINK_CMD_REGION_TAKE_SNAPSHOT. This
>> command is intended to enable userspace to request an immediate snapshot
>> of a region.
>> 
>> Regions can enable support for requestable snapshots by implementing the
>> snapshot callback function in the region's devlink_region_ops structure.
>> 
>> Implementations of this function callback should capture an immediate
>> copy of the data and return it and its destructor in the function
>> parameters. The core devlink code will generate a snapshot ID and create
>> the new snapshot while holding the devlink instance lock.
>
>Does we need a new devlink command to clear the snapshot created by
>DEVLINK_CMD_REGION_TAKE_SNAPSHOT?
>
>It seems the snapshot of a region is only destroyed when unloading
>the driver.

There is existing command to handle this:
devlink region del DEV/REGION snapshot SNAPSHOT_ID

>
>> 
>> Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
>> ---
>>  .../networking/devlink/devlink-region.rst     |  9 +++-
>>  include/net/devlink.h                         |  7 +++
>>  include/uapi/linux/devlink.h                  |  2 +
>>  net/core/devlink.c                            | 46 +++++++++++++++++++
>>  4 files changed, 62 insertions(+), 2 deletions(-)
>> 
>> diff --git a/Documentation/networking/devlink/devlink-region.rst b/Documentation/networking/devlink/devlink-region.rst
>> index 1a7683e7acb2..262249e6c3fc 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_TAKE_SNAPSHOT`` 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 +45,8 @@ 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
>> +    # Request an immediate snapshot, if supported by the region
>> +    $ devlink region snapshot pci/0000:00:05.0/cr-space
>>  
>>      # 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 4a0baa6903cb..63e954241404 100644
>> --- a/include/net/devlink.h
>> +++ b/include/net/devlink.h
>> @@ -498,9 +498,16 @@ typedef void devlink_snapshot_data_dest_t(const void *data);
>>  /**
>>   * struct devlink_region_ops - Region operations
>>   * @name: region name
>> + * @snapshot: callback to request an immediate snapshot. On success,
>> + *            the data and destructor variables must be updated. The function
>> + *            will be called while the devlink instance lock is held.
>>   */
>>  struct devlink_region_ops {
>>  	const char *name;
>> +	int (*snapshot)(struct devlink *devlink,
>> +			struct netlink_ext_ack *extack,
>> +			u8 **data,
>> +			devlink_snapshot_data_dest_t **destructor);
>>  };
>>  
>>  struct devlink_fmsg;
>> diff --git a/include/uapi/linux/devlink.h b/include/uapi/linux/devlink.h
>> index ae37fd4d194a..46643c4320b9 100644
>> --- a/include/uapi/linux/devlink.h
>> +++ b/include/uapi/linux/devlink.h
>> @@ -117,6 +117,8 @@ enum devlink_command {
>>  	DEVLINK_CMD_TRAP_GROUP_NEW,
>>  	DEVLINK_CMD_TRAP_GROUP_DEL,
>>  
>> +	DEVLINK_CMD_REGION_TAKE_SNAPSHOT,
>> +
>>  	/* add new commands above here */
>>  	__DEVLINK_CMD_MAX,
>>  	DEVLINK_CMD_MAX = __DEVLINK_CMD_MAX - 1
>> diff --git a/net/core/devlink.c b/net/core/devlink.c
>> index faf4f4c5c539..574008c536fa 100644
>> --- a/net/core/devlink.c
>> +++ b/net/core/devlink.c
>> @@ -4109,6 +4109,45 @@ static int devlink_nl_cmd_region_read_dumpit(struct sk_buff *skb,
>>  	return err;
>>  }
>>  
>> +static int devlink_nl_cmd_region_take_snapshot(struct sk_buff *skb,
>> +					       struct genl_info *info)
>> +{
>> +	struct devlink *devlink = info->user_ptr[0];
>> +	devlink_snapshot_data_dest_t *destructor;
>> +	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,
>> +				   "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;
>> +	}
>> +
>> +	err = region->ops->snapshot(devlink, info->extack, &data, &destructor);
>> +	if (err)
>> +		return err;
>> +
>> +	snapshot_id = devlink_region_snapshot_id_get_locked(devlink);
>> +	return devlink_region_snapshot_create_locked(region, data, snapshot_id,
>> +						     destructor);
>> +}
>> +
>>  struct devlink_info_req {
>>  	struct sk_buff *msg;
>>  };
>> @@ -6249,6 +6288,13 @@ static const struct genl_ops devlink_nl_ops[] = {
>>  		.flags = GENL_ADMIN_PERM,
>>  		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
>>  	},
>> +	{
>> +		.cmd = DEVLINK_CMD_REGION_TAKE_SNAPSHOT,
>> +		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
>> +		.doit = devlink_nl_cmd_region_take_snapshot,
>> +		.flags = GENL_ADMIN_PERM,
>> +		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
>> +	},
>>  	{
>>  		.cmd = DEVLINK_CMD_INFO_GET,
>>  		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
>> 
>