Re: [PATCH 00/10] implement DEVLINK_CMD_REGION_NEW

[Jiri Pirko <jiri@resnulli.us>]

Tue, Mar 24, 2020 at 11:34:35PM CET, jacob.e.keller@intel.com wrote:
>This series adds support for the DEVLINK_CMD_REGION_NEW operation, used to
>enable userspace requesting a snapshot of a region on demand.
>
>This can be useful to enable adding regions for a driver for which there is
>no trigger to create snapshots. By making this a core part of devlink, there
>is no need for the drivers to use a separate channel such as debugfs.
>
>The primary intent for this kind of region is to expose device information
>that might be useful for diagnostics and information gathering.
>
>The first few patches refactor regions to support a new ops structure for
>extending the available operations that regions can perform. This includes
>converting the destructor into an op from a function argument.
>
>Next, patches refactor the snapshot id allocation to use an xarray which
>tracks the number of current snapshots using a given id. This is done so
>that id lifetime can be determined, and ids can be released when no longer
>in use.
>
>Without this change, snapshot ids remain used forever, until the snapshot_id
>count rolled over UINT_MAX.
>
>Finally, code to enable the previously unused DEVLINK_CMD_REGION_NEW is
>added. This code enforces that the snapshot id is always provided, unlike
>previous revisions of this series.
>
>Finally, a patch is added to enable using this new command via the .snapshot
>callback in both netdevsim and the ice driver.
>
>For the ice driver, a new "nvm-flash" region is added, which will enable
>read access to the NVM flash contents. The intention for this is to allow
>diagnostics tools to gather information about the device. By using a
>snapshot and gathering the NVM contents all at once, the contents can be
>atomic.
>
>General changes since the v2 RFC:
>* Use an xarray instead of IDRs
>* Rebase onto net-next now that the initial ice devlink patches landed.
>
>Patch specific changes:
>* devlink: add functions to take snapshot while locked
>
>  Split this into two patches, so that an explanation of why the
>  devlink_region_snapshot_id_get is still extracted, even though only one
>  caller will remain.

It is much more convenient for reviewing purposes to have the changelog
per-patch.


>
>* devlink: track snapshot ids using an IDR and refcounts
>
>  Convert to using an xarray storing the total number of snapshots directly,
>  rather than an IDR with a refcount structure. This significantly
>  simplifies the code, and avoids the complication of a NULL refcount.
>
>* devlink: implement DEVLINK_CMD_REGION_NEW
>
>  As suggested by Jiri, remove the ability for DEVLINK_CMD_REGION_NEW to
>  dynamically generate IDs. Instead, always require a snapshot id. This
>  aligns with DEVLINK_CMD_REGION_DEL, and helps reduce confusion.
>
>  Refactor this patch to use the xarray instead of the IDR, as in the
>  previous patch.
>
>  Clean up and remove unnecessary new lines on NL_SET_ERR_MSG_MOD
>
>* ice: add a devlink region to dump shadow RAM contents
>
>  Remove the code for immediate region read, as this will be worked on in a
>  separate series following this one.
>
>Jacob Keller (10):
>  devlink: prepare to support region operations
>  devlink: convert snapshot destructor callback to region op
>  devlink: trivial: fix tab in function documentation
>  devlink: add function to take snapshot while locked
>  devlink: extract snapshot id allocation to helper function
>  devlink: convert snapshot id getter to return an error
>  devlink: track snapshot id usage count using an xarray
>  devlink: implement DEVLINK_CMD_REGION_NEW
>  netdevsim: support taking immediate snapshot via devlink
>  ice: add a devlink region for dumping NVM contents
>
> .../networking/devlink/devlink-region.rst     |   8 +
> Documentation/networking/devlink/ice.rst      |  26 ++
> drivers/net/ethernet/intel/ice/ice.h          |   2 +
> drivers/net/ethernet/intel/ice/ice_devlink.c  |  99 +++++
> drivers/net/ethernet/intel/ice/ice_devlink.h  |   3 +
> drivers/net/ethernet/intel/ice/ice_main.c     |   4 +
> drivers/net/ethernet/mellanox/mlx4/crdump.c   |  32 +-
> drivers/net/netdevsim/dev.c                   |  41 +-
> include/net/devlink.h                         |  31 +-
> net/core/devlink.c                            | 354 +++++++++++++++---
> .../drivers/net/netdevsim/devlink.sh          |  15 +
> 11 files changed, 538 insertions(+), 77 deletions(-)
>
>-- 
>2.24.1
>