Patch "scsi: ufs: Stop using the clock scaling lock in the error handler" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    scsi: ufs: Stop using the clock scaling lock in the error handler

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     scsi-ufs-stop-using-the-clock-scaling-lock-in-the-er.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 27b50d4b8710b7699b07650ac8a87bc590e814e0
Author: Bart Van Assche <bvanassche@xxxxxxx>
Date:   Fri Dec 3 15:19:48 2021 -0800

    scsi: ufs: Stop using the clock scaling lock in the error handler
    
    [ Upstream commit 5675c381ea51360b4968b78f23aefda73e3de90d ]
    
    Instead of locking and unlocking the clock scaling lock, surround the
    command queueing code with an RCU reader lock and call synchronize_rcu().
    This patch prepares for removal of the clock scaling lock.
    
    Link: https://lore.kernel.org/r/20211203231950.193369-16-bvanassche@xxxxxxx
    Tested-by: Bean Huo <beanhuo@xxxxxxxxxx>
    Reviewed-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
    Reviewed-by: Bean Huo <beanhuo@xxxxxxxxxx>
    Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
    Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
    Stable-dep-of: 1a5665fc8d7a ("scsi: ufs: core: WLUN suspend SSU/enter hibern8 fail recovery")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index a428b8145dcc..6dd341674110 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -2700,6 +2700,12 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
 	if (!down_read_trylock(&hba->clk_scaling_lock))
 		return SCSI_MLQUEUE_HOST_BUSY;
 
+	/*
+	 * Allows the UFS error handler to wait for prior ufshcd_queuecommand()
+	 * calls.
+	 */
+	rcu_read_lock();
+
 	switch (hba->ufshcd_state) {
 	case UFSHCD_STATE_OPERATIONAL:
 	case UFSHCD_STATE_EH_SCHEDULED_NON_FATAL:
@@ -2766,7 +2772,10 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
 	}
 
 	ufshcd_send_command(hba, tag);
+
 out:
+	rcu_read_unlock();
+
 	up_read(&hba->clk_scaling_lock);
 
 	if (ufs_trigger_eh()) {
@@ -5952,8 +5961,7 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
 	}
 	ufshcd_scsi_block_requests(hba);
 	/* Drain ufshcd_queuecommand() */
-	down_write(&hba->clk_scaling_lock);
-	up_write(&hba->clk_scaling_lock);
+	synchronize_rcu();
 	cancel_work_sync(&hba->eeh_work);
 }