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Message-ID: <89fcf83b-7253-297a-3cf6-4caa89332cf1@intel.com>
Date: Fri, 1 May 2020 14:32:20 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net,
jiri@...nulli.us
Cc: netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH net-next v3 2/3] devlink: let kernel allocate region
snapshot id
On 4/30/2020 10:57 AM, Jakub Kicinski wrote:
> Currently users have to choose a free snapshot id before
> calling DEVLINK_CMD_REGION_NEW. This is potentially racy
> and inconvenient.
>
> Make the DEVLINK_ATTR_REGION_SNAPSHOT_ID optional and try
> to allocate id automatically. Send a message back to the
> caller with the snapshot info.
>
> Example use:
> $ devlink region new netdevsim/netdevsim1/dummy
> netdevsim/netdevsim1/dummy: snapshot 1
>
> $ id=$(devlink -j region new netdevsim/netdevsim1/dummy | \
> jq '.[][][][]')
> $ devlink region dump netdevsim/netdevsim1/dummy snapshot $id
> [...]
> $ devlink region del netdevsim/netdevsim1/dummy snapshot $id
>
> v3:
> - send the notification only once snapshot creation completed.
> v2:
> - don't wrap the line containing extack;
> - add a few sentences to the docs.
>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
> .../networking/devlink/devlink-region.rst | 7 +-
> net/core/devlink.c | 69 +++++++++++++++----
> .../drivers/net/netdevsim/devlink.sh | 13 ++++
> 3 files changed, 74 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/networking/devlink/devlink-region.rst b/Documentation/networking/devlink/devlink-region.rst
> index 04e04d1ff627..daf35427fce1 100644
> --- a/Documentation/networking/devlink/devlink-region.rst
> +++ b/Documentation/networking/devlink/devlink-region.rst
> @@ -23,7 +23,9 @@ 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.
> +in its ``devlink_region_ops`` structure. If snapshot id is not set in
> +the ``DEVLINK_CMD_REGION_NEW`` request kernel will allocate one and send
> +the snapshot information to user space.
>
> example usage
> -------------
> @@ -45,7 +47,8 @@ example usage
> $ devlink region del pci/0000:00:05.0/cr-space snapshot 1
>
> # Request an immediate snapshot, if supported by the region
> - $ devlink region new pci/0000:00:05.0/cr-space snapshot 5
> + $ devlink region new pci/0000:00:05.0/cr-space
> + 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/net/core/devlink.c b/net/core/devlink.c
> index 92afb85bad89..4df947fb90d9 100644
> --- a/net/core/devlink.c
> +++ b/net/core/devlink.c
> @@ -4082,10 +4082,41 @@ static int devlink_nl_cmd_region_del(struct sk_buff *skb,
> return 0;
> }
>
> +static int
> +devlink_nl_snapshot_id_notify(struct devlink *devlink, struct genl_info *info,
> + struct devlink_region *region, u32 snapshot_id)
> +{
> + struct devlink_snapshot *snapshot;
> + struct sk_buff *msg;
> + int err;
> +
> + snapshot = devlink_region_snapshot_get_by_id(region, snapshot_id);
> + if (WARN_ON(!snapshot))
> + return -EINVAL;
> +
> + msg = devlink_nl_region_notify_build(region, snapshot,
> + DEVLINK_CMD_REGION_NEW,
> + info->snd_portid, info->snd_seq);
> + err = PTR_ERR_OR_ZERO(msg);
> + if (err)
> + goto err_notify;
> +
> + err = genlmsg_reply(msg, info);
> + if (err)
> + goto err_notify;
> +
> + return 0;
> +
> +err_notify:
> + devlink_region_snapshot_del(region, snapshot);
> + return err;
> +}
> +
> static int
> devlink_nl_cmd_region_new(struct sk_buff *skb, struct genl_info *info)
> {
> struct devlink *devlink = info->user_ptr[0];
> + struct nlattr *snapshot_id_attr;
> struct devlink_region *region;
> const char *region_name;
> u32 snapshot_id;
> @@ -4097,11 +4128,6 @@ devlink_nl_cmd_region_new(struct sk_buff *skb, struct genl_info *info)
> return -EINVAL;
> }
>
> - if (!info->attrs[DEVLINK_ATTR_REGION_SNAPSHOT_ID]) {
> - NL_SET_ERR_MSG_MOD(info->extack, "No snapshot id provided");
> - return -EINVAL;
> - }
> -
> region_name = nla_data(info->attrs[DEVLINK_ATTR_REGION_NAME]);
> region = devlink_region_get_by_name(devlink, region_name);
> if (!region) {
> @@ -4119,16 +4145,25 @@ devlink_nl_cmd_region_new(struct sk_buff *skb, struct genl_info *info)
> return -ENOSPC;
> }
>
> - snapshot_id = nla_get_u32(info->attrs[DEVLINK_ATTR_REGION_SNAPSHOT_ID]);
> + snapshot_id_attr = info->attrs[DEVLINK_ATTR_REGION_SNAPSHOT_ID];
> + if (snapshot_id_attr) {
> + snapshot_id = nla_get_u32(snapshot_id_attr);
>
> - 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;
> - }
> + 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;
> + }
>
> - err = __devlink_snapshot_id_insert(devlink, snapshot_id);
> - if (err)
> - return err;
> + err = __devlink_snapshot_id_insert(devlink, snapshot_id);
> + if (err)
> + return err;
> + } else {
> + err = __devlink_region_snapshot_id_get(devlink, &snapshot_id);
> + if (err) {
> + NL_SET_ERR_MSG_MOD(info->extack, "Failed to allocate a new snapshot id");
> + return err;
> + }
> + }
>
> err = region->ops->snapshot(devlink, info->extack, &data);
> if (err)
> @@ -4138,6 +4173,14 @@ devlink_nl_cmd_region_new(struct sk_buff *skb, struct genl_info *info)
> if (err)
> goto err_snapshot_create;
>
> + if (!snapshot_id_attr) {
> + /* destroys the snapshot on failure */
> + err = devlink_nl_snapshot_id_notify(devlink, info,
> + region, snapshot_id);
> + if (err)
> + return err;
> + }
> +
Does it make sense to report back the snapshot in all cases? I guess no,
since the caller knows the id, and it doesn't really simplify anything
to display this if you know the id already. Ok.
Thanks for this, I really like how this simplifies creating a snapshot!
-Jake
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