scsi: sd: Rely on the driver core for asynchronous probing

As explained during the 2018 LSF/MM session about increasing SCSI disk
probing concurrency, the problems with the current probing approach are as
follows:

 - The driver core is unaware of asynchronous SCSI LUN probing.
   wait_for_device_probe() waits for all asynchronous probes except
   asynchronous SCSI disk probes.

 - There is unnecessary serialization between sd_probe() and sd_remove().
   This can lead to a deadlock.

Hence this patch that modifies the sd driver such that it uses the driver
core framework for asynchronous probing. The async domain and
get_device()/put_device() pairs that became superfluous due to this change
are removed.

This patch does not affect the time needed for loading the scsi_debug
kernel module with parameters delay=0 and max_luns=256.

This patch depends on commit ef0ff68351be ("driver core: Probe devices
asynchronously instead of the driver") that went upstream in kernel version
v5.1-rc1.

Cc: Lee Duncan <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Luis Chamberlain <[email protected]>
Cc: Johannes Thumshirn <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Dan Williams <[email protected]>
Signed-off-by: Bart Van Assche <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>

0 files changed, 0 insertions, 0 deletions