Merge branch 'implement-DEVLINK_CMD_REGION_NEW'

Jacob Keller says:

====================
implement DEVLINK_CMD_REGION_NEW

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.

Links to previous discussions:
1st RFC - https://lore.kernel.org/netdev/20200130225913.1671982-1-jacob.e.keller@intel.com/
2nd RFC - https://lore.kernel.org/netdev/20200214232223.3442651-1-jacob.e.keller@intel.com/
v1 - https://lore.kernel.org/netdev/20200324223445.2077900-1-jacob.e.keller@intel.com/
v2 - https://lore.kernel.org/netdev/20200326035157.2211090-1-jacob.e.keller@intel.com/

Major changes since RFC:
* use an xarray for tracking snapshot ids, rather than an IDR
* remove support for auto-generated snapshot ids in DEVLINK_CMD_REGION_NEW

See each patch for an individual changelog per-patch
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 9 deletions

diff --git a/include/net/devlink.h b/include/net/devlink.h
index 37230e23b5b0..a1a02cd5890b 100644
--- a/include/net/devlink.h
+++ b/include/net/devlink.h
@@ -18,6 +18,7 @@
 #include <net/net_namespace.h>
 #include <net/flow_offload.h>
 #include <uapi/linux/devlink.h>
+#include <linux/xarray.h>
 
 struct devlink_ops;
 
@@ -29,13 +30,13 @@ struct devlink {
 	struct list_head resource_list;
 	struct list_head param_list;
 	struct list_head region_list;
-	u32 snapshot_id;
 	struct list_head reporter_list;
 	struct mutex reporters_lock; /* protects reporter_list */
 	struct devlink_dpipe_headers *dpipe_headers;
 	struct list_head trap_list;
 	struct list_head trap_group_list;
 	const struct devlink_ops *ops;
+	struct xarray snapshot_ids;
 	struct device *dev;
 	possible_net_t _net;
 	struct mutex lock;
@@ -496,7 +497,21 @@ enum devlink_param_generic_id {
 struct devlink_region;
 struct devlink_info_req;
 
-typedef void devlink_snapshot_data_dest_t(const void *data);
+/**
+ * struct devlink_region_ops - Region operations
+ * @name: region name
+ * @destructor: callback used to free snapshot memory when deleting
+ * @snapshot: callback to request an immediate snapshot. On success,
+ *            the data variable must be updated to point to the snapshot data.
+ *            The function will be called while the devlink instance lock is
+ *            held.
+ */
+struct devlink_region_ops {
+	const char *name;
+	void (*destructor)(const void *data);
+	int (*snapshot)(struct devlink *devlink, struct netlink_ext_ack *extack,
+			u8 **data);
+};
 
 struct devlink_fmsg;
 struct devlink_health_reporter;
@@ -963,15 +978,15 @@ void devlink_port_param_value_changed(struct devlink_port *devlink_port,
 				      u32 param_id);
 void devlink_param_value_str_fill(union devlink_param_value *dst_val,
 				  const char *src);
-struct devlink_region *devlink_region_create(struct devlink *devlink,
-					     const char *region_name,
-					     u32 region_max_snapshots,
-					     u64 region_size);
+struct devlink_region *
+devlink_region_create(struct devlink *devlink,
+		      const struct devlink_region_ops *ops,
+		      u32 region_max_snapshots, u64 region_size);
 void devlink_region_destroy(struct devlink_region *region);
-u32 devlink_region_snapshot_id_get(struct devlink *devlink);
+int devlink_region_snapshot_id_get(struct devlink *devlink, u32 *id);
+void devlink_region_snapshot_id_put(struct devlink *devlink, u32 id);
 int devlink_region_snapshot_create(struct devlink_region *region,
-				   u8 *data, u32 snapshot_id,
-				   devlink_snapshot_data_dest_t *data_destructor);
+				   u8 *data, u32 snapshot_id);
 int devlink_info_serial_number_put(struct devlink_info_req *req,
 				   const char *sn);
 int devlink_info_driver_name_put(struct devlink_info_req *req,