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Date: Mon, 3 Feb 2020 16:19:23 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Jacob Keller <jacob.e.keller@...el.com>, <netdev@...r.kernel.org>
CC: <jiri@...nulli.us>, <valex@...lanox.com>, <lihong.yang@...el.com>
Subject: Re: [PATCH 03/15] devlink: add operation to take an immediate
snapshot
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.
>
> Signed-off-by: Jacob Keller <jacob.e.keller@...el.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,
>
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