[PATCH iproute2-next] devlink: support direct region read requests

[PATCH iproute2-next] devlink: support direct region read requests

[Jacob Keller]

The kernel has gained support for reading from regions without needing to
create a snapshot. To use this support, the DEVLINK_ATTR_REGION_DIRECT
attribute must be added to the command.

For the "read" command, if the user did not specify a snapshot, add the new
attribute to request a direct read. The "dump" command will still require a
snapshot. While technically a dump could be performed without a snapshot it
is not guaranteed to be atomic unless the region size is no larger than
256 bytes.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
This depends on https://lore.kernel.org/netdev/20221128203647.1198669-1-jacob.e.keller@intel.com/T/#t

 devlink/devlink.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/devlink/devlink.c b/devlink/devlink.c
index 8aefa101b2f8..5057b09505ef 100644
--- a/devlink/devlink.c
+++ b/devlink/devlink.c
@@ -8535,11 +8535,15 @@ static int cmd_region_read(struct dl *dl)
 	int err;
 
 	err = dl_argv_parse(dl, DL_OPT_HANDLE_REGION | DL_OPT_REGION_ADDRESS |
-			    DL_OPT_REGION_LENGTH | DL_OPT_REGION_SNAPSHOT_ID,
-			    0);
+			    DL_OPT_REGION_LENGTH,
+			    DL_OPT_REGION_SNAPSHOT_ID);
 	if (err)
 		return err;
 
+	/* If user didn't provide a snapshot id, perform a direct read */
+	if (!(dl->opts.present & DL_OPT_REGION_SNAPSHOT_ID))
+		mnl_attr_put(nlh, DEVLINK_ATTR_REGION_DIRECT, 0, NULL);
+
 	nlh = mnlu_gen_socket_cmd_prepare(&dl->nlg, DEVLINK_CMD_REGION_READ,
 			       NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP);
 

base-commit: 2ed09c3bf8aca185b2f3eb369ae435503f9b9826
-- 
2.38.1.420.g319605f8f00e

Re: [PATCH iproute2-next] devlink: support direct region read requests

[David Ahern]

> diff --git a/devlink/devlink.c b/devlink/devlink.c
> index 8aefa101b2f8..5057b09505ef 100644
> --- a/devlink/devlink.c
> +++ b/devlink/devlink.c
> @@ -8535,11 +8535,15 @@ static int cmd_region_read(struct dl *dl)
>  	int err;
>  
>  	err = dl_argv_parse(dl, DL_OPT_HANDLE_REGION | DL_OPT_REGION_ADDRESS |
> -			    DL_OPT_REGION_LENGTH | DL_OPT_REGION_SNAPSHOT_ID,
> -			    0);
> +			    DL_OPT_REGION_LENGTH,
> +			    DL_OPT_REGION_SNAPSHOT_ID);
>  	if (err)
>  		return err;
>  
> +	/* If user didn't provide a snapshot id, perform a direct read */
> +	if (!(dl->opts.present & DL_OPT_REGION_SNAPSHOT_ID))
> +		mnl_attr_put(nlh, DEVLINK_ATTR_REGION_DIRECT, 0, NULL);
> +
>  	nlh = mnlu_gen_socket_cmd_prepare(&dl->nlg, DEVLINK_CMD_REGION_READ,
>  			       NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP);
>  
> 
> base-commit: 2ed09c3bf8aca185b2f3eb369ae435503f9b9826
> -- 
> 2.38.1.420.g319605f8f00e
> 

This introduces a compile warning:

devlink.c: In function ‘dl_cmd’:
devlink.c:8613:3: warning: ‘nlh’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 8613 |   mnl_attr_put(nlh, DEVLINK_ATTR_REGION_DIRECT, 0, NULL);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
devlink.c:8602:19: note: ‘nlh’ was declared here

and always add maintainers to iproute2 patches.