Currently streams are only freed when:
- They have no referencing zfetch and and their I/O references
go to zero.
- They are more than 2s old and a new I/O request comes in on
the same zfetch.
This means that we will leak unreferenced streams when their zfetch
structure is freed.
This change checks the reference count on a stream at zfetch free
time. If it is zero we free it immediately. If it has remaining
references we allow the prefetch callback to free it at I/O
completion time.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Adam Moss <c@yotes.com>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes#11052
57dc5d42b1