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Message-ID: <02874ECE860811409154E81DA85FBB58B6CF8474@FMSMSX102.amr.corp.intel.com>
Date: Thu, 30 Apr 2020 00:33:43 +0000
From: "Keller, Jacob E" <jacob.e.keller@...el.com>
To: Jakub Kicinski <kuba@...nel.org>,
"davem@...emloft.net" <davem@...emloft.net>,
"jiri@...nulli.us" <jiri@...nulli.us>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"kernel-team@...com" <kernel-team@...com>
Subject: RE: [PATCH net-next v2] devlink: let kernel allocate region
snapshot id
> -----Original Message-----
> From: netdev-owner@...r.kernel.org <netdev-owner@...r.kernel.org> On
> Behalf Of Jakub Kicinski
> Sent: Wednesday, April 29, 2020 4:38 PM
> To: davem@...emloft.net; jiri@...nulli.us
> Cc: netdev@...r.kernel.org; kernel-team@...com; Keller, Jacob E
> <jacob.e.keller@...el.com>; Jakub Kicinski <kuba@...nel.org>
> Subject: [PATCH net-next v2] devlink: let kernel allocate region snapshot id
>
> 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.
>
> The message carrying id gets sent immediately, but the
> allocation is only valid if the entire operation succeeded.
> This makes life easier, as sending the notification itself
> may fail.
I like this. Not having to plan ahead and pick a random id is pretty useful, and this helps avoid some of the race that could occur around this.
Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
Thanks,
Jake
>
> 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
>
> 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 | 10 ++-
> net/core/devlink.c | 83 ++++++++++++++++---
> .../drivers/net/netdevsim/devlink.sh | 13 +++
> 3 files changed, 91 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/networking/devlink/devlink-region.rst
> b/Documentation/networking/devlink/devlink-region.rst
> index 04e04d1ff627..b163d09a3d0d 100644
> --- a/Documentation/networking/devlink/devlink-region.rst
> +++ b/Documentation/networking/devlink/devlink-region.rst
> @@ -23,7 +23,12 @@ 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. Note that receiving the snapshot
> +information does not guarantee that the snapshot creation completed
> +successfully, user space must check the status of the operation before
> +proceeding.
>
> example usage
> -------------
> @@ -45,7 +50,8 @@ 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 1ec2e9fd8898..82703be1032e 100644
> --- a/net/core/devlink.c
> +++ b/net/core/devlink.c
> @@ -4065,10 +4065,64 @@ static int devlink_nl_cmd_region_del(struct sk_buff
> *skb,
> return 0;
> }
>
> +static int
> +devlink_nl_alloc_snapshot_id(struct devlink *devlink, struct genl_info *info,
> + struct devlink_region *region, u32 *snapshot_id)
> +{
> + struct sk_buff *msg;
> + void *hdr;
> + int err;
> +
> + 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;
> + }
> +
> + msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
> + if (!msg) {
> + err = -ENOMEM;
> + goto err_msg_alloc;
> + }
> +
> + hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
> + &devlink_nl_family, 0, DEVLINK_CMD_REGION_NEW);
> + if (!hdr) {
> + err = -EMSGSIZE;
> + goto err_put_failure;
> + }
> + err = devlink_nl_put_handle(msg, devlink);
> + if (err)
> + goto err_attr_failure;
> + err = nla_put_string(msg, DEVLINK_ATTR_REGION_NAME, region->ops-
> >name);
> + if (err)
> + goto err_attr_failure;
> + err = nla_put_u32(msg, DEVLINK_ATTR_REGION_SNAPSHOT_ID,
> *snapshot_id);
> + if (err)
> + goto err_attr_failure;
> + genlmsg_end(msg, hdr);
> +
> + err = genlmsg_reply(msg, info);
> + if (err)
> + goto err_reply;
> +
> + return 0;
> +
> +err_attr_failure:
> + genlmsg_cancel(msg, hdr);
> +err_put_failure:
> + nlmsg_free(msg);
> +err_msg_alloc:
> +err_reply:
> + __devlink_snapshot_id_decrement(devlink, *snapshot_id);
> + 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;
> @@ -4080,11 +4134,6 @@ 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) {
> @@ -4102,16 +4151,24 @@ 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_nl_alloc_snapshot_id(devlink, info,
> + region, &snapshot_id);
> + if (err)
> + return err;
> + }
>
> err = region->ops->snapshot(devlink, info->extack, &data);
> if (err)
> diff --git a/tools/testing/selftests/drivers/net/netdevsim/devlink.sh
> b/tools/testing/selftests/drivers/net/netdevsim/devlink.sh
> index 9f9741444549..ad539eccddcb 100755
> --- a/tools/testing/selftests/drivers/net/netdevsim/devlink.sh
> +++ b/tools/testing/selftests/drivers/net/netdevsim/devlink.sh
> @@ -151,6 +151,19 @@ regions_test()
>
> check_region_snapshot_count dummy post-second-delete 2
>
> + sid=$(devlink -j region new $DL_HANDLE/dummy | jq '.[][][][]')
> + check_err $? "Failed to create a new snapshot with id allocated by the
> kernel"
> +
> + check_region_snapshot_count dummy post-first-request 3
> +
> + devlink region dump $DL_HANDLE/dummy snapshot $sid >> /dev/null
> + check_err $? "Failed to dump a snapshot with id allocated by the kernel"
> +
> + devlink region del $DL_HANDLE/dummy snapshot $sid
> + check_err $? "Failed to delete snapshot with id allocated by the kernel"
> +
> + check_region_snapshot_count dummy post-first-request 2
> +
> log_test "regions test"
> }
>
> --
> 2.25.4
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