block: introduce BLK_STS_OFFLINE

block: introduce BLK_STS_OFFLINE

Currently, drivers reports BLK_STS_IOERR for devices that are not full
online or being removed. This behavior could cause confusion for users,
as they are not really I/O errors from the device.

Solve this issue with a new state BLK_STS_OFFLINE, which reports "device
offline error" in dmesg instead of "I/O error".

EIO is intentionally kept to not change user visible return value.

Signed-off-by: Song Liu <song@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220203192827.1370270-2-song@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>