• Jacob Keller's avatar
    devlink: track snapshot id usage count using an xarray · 12102436
    Jacob Keller authored
    Each snapshot created for a devlink region must have an id. These ids
    are supposed to be unique per "event" that caused the snapshot to be
    created. Drivers call devlink_region_snapshot_id_get to obtain a new id
    to use for a new event trigger. The id values are tracked per devlink,
    so that the same id number can be used if a triggering event creates
    multiple snapshots on different regions.
    
    There is no mechanism for snapshot ids to ever be reused. Introduce an
    xarray to store the count of how many snapshots are using a given id,
    replacing the snapshot_id field previously used for picking the next id.
    
    The devlink_region_snapshot_id_get() function will use xa_alloc to
    insert an initial value of 1 value at an available slot between 0 and
    U32_MAX.
    
    The new __devlink_snapshot_id_increment() and
    __devlink_snapshot_id_decrement() functions will be used to track how
    many snapshots currently use an id.
    
    Drivers must now call devlink_snapshot_id_put() in order to release
    their reference of the snapshot id after adding region snapshots.
    
    By tracking the total number of snapshots using a given id, it is
    possible for the decrement() function to erase the id from the xarray
    when it is not in use.
    
    With this method, a snapshot id can become reused again once all
    snapshots that referred to it have been deleted via
    DEVLINK_CMD_REGION_DEL, and the driver has finished adding snapshots.
    
    This work also paves the way to introduce a mechanism for userspace to
    request a snapshot.
    Signed-off-by: default avatarJacob Keller <jacob.e.keller@intel.com>
    Reviewed-by: default avatarJiri Pirko <jiri@mellanox.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    12102436
dev.c 29.5 KB