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 <lduncan@suse.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 49821f1..8128165 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -86,15 +86,10 @@ unsigned int scsi_logging_level;
EXPORT_SYMBOL(scsi_logging_level);
#endif
-/* sd, scsi core and power management need to coordinate flushing async actions */
-ASYNC_DOMAIN(scsi_sd_probe_domain);
-EXPORT_SYMBOL(scsi_sd_probe_domain);
-
/*
- * Separate domain (from scsi_sd_probe_domain) to maximize the benefit of
- * asynchronous system resume operations. It is marked 'exclusive' to avoid
- * being included in the async_synchronize_full() that is invoked by
- * dpm_resume()
+ * Domain for asynchronous system resume operations. It is marked 'exclusive'
+ * to avoid being included in the async_synchronize_full() that is invoked by
+ * dpm_resume().
*/
ASYNC_DOMAIN_EXCLUSIVE(scsi_sd_pm_domain);
EXPORT_SYMBOL(scsi_sd_pm_domain);
@@ -821,7 +816,6 @@ static void __exit exit_scsi(void)
scsi_exit_devinfo();
scsi_exit_procfs();
scsi_exit_queue();
- async_unregister_domain(&scsi_sd_probe_domain);
}
subsys_initcall(init_scsi);