For async page writeback, we do not need to wait for the page to be on
disk before returning to the caller; it's enough that the data from the
dirty page be on the DMU and in the in-memory ZIL, just like any other
write.
So, if this is not a syncing write, don't add a callback to the itx, and
instead just unlock the page immediately.
(This is effectively the same concept used for FreeBSD in d323fbf49c).
Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Closes#17584Closes#14290
b9c45fe68c