scsi: ufs: core: Don't perform UFS clkscaling during host async scan

When preparing for UFS clock scaling, the UFS driver will quiesce all
sdevs queues in the UFS SCSI host tagset list and then unquiesce them in
ufshcd_clock_scaling_unprepare(). If the UFS SCSI host async scan is in
progress at this time, some LUs may be added to the tagset list between
UFS clkscale prepare and unprepare. This can cause two issues:

1. During clock scaling, there may be I/O requests issued through new
added queues that have not been quiesced, leading to task abort issue.

2. These new added queues that have not been quiesced will be unquiesced
as well when UFS clkscale is unprepared, resulting in warning prints.

Therefore, use the mutex lock scan_mutex in
ufshcd_clock_scaling_prepare() and ufshcd_clock_scaling_unprepare() to
protect it.

Co-developed-by: Can Guo <[e-mail]>
Signed-off-by: Can Guo <[e-mail]>
Signed-off-by: Ziqi Chen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Suggested-by: Bart Van Assche <[e-mail]>
Reviewed-by: Bart Van Assche <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/ufs/core/ufshcd.c

···
 	 * make sure that there are no outstanding requests when
 	 * clock scaling is in progress
 	 */
+	mutex_lock(&hba->host->scan_mutex);
 	blk_mq_quiesce_tagset(&hba->host->tag_set);
 	mutex_lock(&hba->wb_mutex);
 	down_write(&hba->clk_scaling_lock);
···
 		up_write(&hba->clk_scaling_lock);
 		mutex_unlock(&hba->wb_mutex);
 		blk_mq_unquiesce_tagset(&hba->host->tag_set);
+		mutex_unlock(&hba->host->scan_mutex);
 		goto out;
 	}
 
···
 	mutex_unlock(&hba->wb_mutex);
 
 	blk_mq_unquiesce_tagset(&hba->host->tag_set);
+	mutex_unlock(&hba->host->scan_mutex);
 	ufshcd_release(hba);
 }