Some paths through be_exists will set the error state, others will not
There are multiple reasons that a call can fail, so clean it up a bit: all
paths now return an appropriate error code so the caller can attempt to
distinguish between a BE legitimately not existing and just having the wrong
mountpoint. The caller is expected to bubble the error through to the
internal error handler as needed.
This fixes some unfriendliness with bectl(8)'s activate subcommand, where
it might fail due to a bad mountpoint but the only message output is a
generic "failed to activate" message.
Approved by: re (gjb)
be_add_child functionality gets split out into separate places as a bonus.
A lot of places here we'll gloss over libzfs errors, because they shouldn't
be happening given the conditions that we're operating under. "Unknown
error" is what I'm intending to use for the moment to indicate an
exceptional circumstance- exceptional enough that we can't tell the consumer
did because we're not so certain that they did anything.
- File names don't necessarily need to be repeated
- Add SPDX tags
- Add a missing copyright for Kyle Kneitinger in bectl.8, originally written
by him in GSoC 2017; his standard copyright notice has been copied from
other files within the same directory to remain consistent with how he
clearly wished to portray it
