Looks like it's in master-next (-31.33). See https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/bionic/commit/?h=master-next and https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/bionic/tree/block/blk-core.c?id=Ubuntu-4.15.0-31.33#n856
Looks like it's in master-next (-31.33). See https:/ /git.launchpad. net/~ubuntu- kernel/ ubuntu/ +source/ linux/+ git/bionic/ commit/ ?h=master- next and https:/ /git.launchpad. net/~ubuntu- kernel/ ubuntu/ +source/ linux/+ git/bionic/ tree/block/ blk-core. c?id=Ubuntu- 4.15.0- 31.33#n856