Upon inspection of our code, I noticed that we assume that
__alloc_percpu() cannot fail, and while it probably never has failed in
practice, technically, it can fail, so we should handle that.
Additionally, we incorrectly assume that `taskq_create()` in
spl_kmem_cache_init() cannot fail. The same remark applies to it.
Lastly, `spl-init()` failures should always return negative error
values, but in some places, we are returning positive 1, which is
incorrect. We change those values to their correct error codes.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes#13847