Re: [PATCH net-next v2] netlink: add tracepoint at NL_SET_ERR_MSG

On Wed, Feb 03, 2021 at 10:48:16PM -0300, Marcelo Ricardo Leitner wrote:

From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Often userspace won't request the extack information, or they don't log it
because of log level or so, and even when they do, sometimes it's not
enough to know exactly what caused the error.

Netlink extack is the standard way of reporting erros with descriptive
error messages. With a trace point on it, we then can know exactly where
the error happened, regardless of userspace app. Also, we can even see if
the err msg was overwritten.

The wrapper do_trace_netlink_extack() is because trace points shouldn't be
called from .h files, as trace points are not that small, and the function
call to do_trace_netlink_extack() on the macros is not protected by
tracepoint_enabled() because the macros are called from modules, and this
would require exporting some trace structs. As this is error path, it's
better to export just the wrapper instead.

v2: removed leftover tracepoint declaration

Whoops, missed a blank line here.
Please just let me know if I should send a new one.
Thanks.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>