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 <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

block/blk-core.c

@@ -164,6 +164,7 @@ static const struct {
 	[BLK_STS_RESOURCE]	= { -ENOMEM,	"kernel resource" },
 	[BLK_STS_DEV_RESOURCE]	= { -EBUSY,	"device resource" },
 	[BLK_STS_AGAIN]		= { -EAGAIN,	"nonblocking retry" },
+	[BLK_STS_OFFLINE]	= { -EIO,	"device offline" },
 
 	/* device mapper special case, should not leak out: */
 	[BLK_STS_DM_REQUEUE]	= { -EREMCHG, "dm internal retry" },

include/linux/blk_types.h

@@ -153,6 +153,13 @@ typedef u8 __bitwise blk_status_t;
  */
 #define BLK_STS_ZONE_ACTIVE_RESOURCE	((__force blk_status_t)16)
 
+/*
+ * BLK_STS_OFFLINE is returned from the driver when the target device is offline
+ * or is being taken offline. This could help differentiate the case where a
+ * device is intentionally being shut down from a real I/O error.
+ */
+#define BLK_STS_OFFLINE		((__force blk_status_t)17)
+
 /**
  * blk_path_error - returns true if error may be path related
  * @error: status the request was completed with