fusefs: convert debug printfs into dtrace probes
fuse(4) was heavily instrumented with debug printf statements that could
only be enabled with compile-time flags. They fell into three basic groups:
- Totally redundant with dtrace FBT probes. These I deleted.
- Print textual information, usually error messages. These I converted to SDT probes of the form fuse:fuse:FILE:trace. They work just like the old printf statements except they can be enabled at runtime with dtrace. They can be filtered by FILE and/or by priority.
- More complicated probes that print detailed information. These I converted into ad-hoc SDT probes.
Also, de-inline fuse_internal_cache_attrs. It's big enough to be a regular
function, and this way it gets a dtrace FBT probe.
This commit is a merge of r345304, r344914, r344703, and r344664 from
projects/fuse2.
Reviewed by: cem
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D19667