scsi: ufs: Fix a race condition between ufshcd_abort() and eh_work()

In current task abort routine, if task abort happens to the device W-LUN,
the code directly jumps to ufshcd_eh_host_reset_handler() to perform a full
reset and restore then returns FAIL or SUCCESS. Commands sent to the device
W-LUN are most likely the SSU cmds sent during UFS PM operations. If such
SSU cmd enters task abort routine when ufshcd_eh_host_reset_handler()
flushes eh_work, it will get stuck there since err_handler is serialized
with PM operations.

In order to unblock above call path, we merely clean up the lrb taken by
this cmd, queue the eh_work and return SUCCESS. Once the cmd is aborted,
the PM operation which sends out the cmd just errors out, then err_handler
shall be able to proceed with the full reset and restore.

In this scenario, the cmd is aborted even before it is actually cleared by
HW, set the lrb->in_use flag to prevent subsequent cmds, including SCSI
cmds and dev cmds, from taking the lrb released from abort. The flag shall
evetually be cleared in __ufshcd_transfer_req_compl() invoked by the full
reset and restore from err_handler.

[mkp: conflict with event logging series]

Link: https://lore.kernel.org/r/1606910644-21185-3-git-send-email-cang@codeaurora.org
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

2 files changed, 51 insertions, 15 deletions

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index b7a22a7c1aa0..d94a376bb194 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -2558,6 +2558,14 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
 		(hba->clk_gating.state != CLKS_ON));
 
 	lrbp = &hba->lrb[tag];
+	if (unlikely(lrbp->in_use)) {
+		if (hba->pm_op_in_progress)
+			set_host_byte(cmd, DID_BAD_TARGET);
+		else
+			err = SCSI_MLQUEUE_HOST_BUSY;
+		ufshcd_release(hba);
+		goto out;
+	}
 
 	WARN_ON(lrbp->cmd);
 	lrbp->cmd = cmd;
@@ -2800,6 +2808,11 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
 
 	init_completion(&wait);
 	lrbp = &hba->lrb[tag];
+	if (unlikely(lrbp->in_use)) {
+		err = -EBUSY;
+		goto out;
+	}
+
 	WARN_ON(lrbp->cmd);
 	err = ufshcd_compose_dev_cmd(hba, lrbp, cmd_type, tag);
 	if (unlikely(err))
@@ -2816,6 +2829,7 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
 
 	err = ufshcd_wait_for_dev_cmd(hba, lrbp, timeout);
 
+out:
 	ufshcd_add_query_upiu_trace(hba, tag,
 			err ? "query_complete_err" : "query_complete");
 
@@ -4980,9 +4994,11 @@ static void __ufshcd_transfer_req_compl(struct ufs_hba *hba,
 	struct scsi_cmnd *cmd;
 	int result;
 	int index;
+	bool update_scaling = false;
 
 	for_each_set_bit(index, &completed_reqs, hba->nutrs) {
 		lrbp = &hba->lrb[index];
+		lrbp->in_use = false;
 		lrbp->compl_time_stamp = ktime_get();
 		cmd = lrbp->cmd;
 		if (cmd) {
@@ -4995,15 +5011,17 @@ static void __ufshcd_transfer_req_compl(struct ufs_hba *hba,
 			/* Do not touch lrbp after scsi done */
 			cmd->scsi_done(cmd);
 			__ufshcd_release(hba);
+			update_scaling = true;
 		} else if (lrbp->command_type == UTP_CMD_TYPE_DEV_MANAGE ||
 			lrbp->command_type == UTP_CMD_TYPE_UFS_STORAGE) {
 			if (hba->dev_cmd.complete) {
 				ufshcd_add_command_trace(hba, index,
 						"dev_complete");
 				complete(hba->dev_cmd.complete);
+				update_scaling = true;
 			}
 		}
-		if (ufshcd_is_clkscaling_supported(hba))
+		if (ufshcd_is_clkscaling_supported(hba) && update_scaling)
 			hba->clk_scaling.active_reqs--;
 	}
 
@@ -6426,8 +6444,12 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba,
 
 	init_completion(&wait);
 	lrbp = &hba->lrb[tag];
-	WARN_ON(lrbp->cmd);
+	if (unlikely(lrbp->in_use)) {
+		err = -EBUSY;
+		goto out;
+	}
 
+	WARN_ON(lrbp->cmd);
 	lrbp->cmd = NULL;
 	lrbp->sense_bufflen = 0;
 	lrbp->sense_buffer = NULL;
@@ -6499,6 +6521,7 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba,
 		}
 	}
 
+out:
 	blk_put_request(req);
 out_unlock:
 	up_read(&hba->clk_scaling_lock);
@@ -6749,18 +6772,6 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
 		BUG();
 	}
 
-	/*
-	 * Task abort to the device W-LUN is illegal. When this command
-	 * will fail, due to spec violation, scsi err handling next step
-	 * will be to send LU reset which, again, is a spec violation.
-	 * To avoid these unnecessary/illegal step we skip to the last error
-	 * handling stage: reset and restore.
-	 */
-	if (lrbp->lun == UFS_UPIU_UFS_DEVICE_WLUN) {
-		ufshcd_update_evt_hist(hba, UFS_EVT_ABORT, lrbp->lun);
-		return ufshcd_eh_host_reset_handler(cmd);
-	}
-
 	ufshcd_hold(hba, false);
 	reg = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL);
 	/* If command is already aborted/completed, return SUCCESS */
@@ -6781,7 +6792,7 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
 	 * to reduce repeated printouts. For other aborted requests only print
 	 * basic details.
 	 */
-	scsi_print_command(hba->lrb[tag].cmd);
+	scsi_print_command(cmd);
 	if (!hba->req_abort_count) {
 		ufshcd_update_evt_hist(hba, UFS_EVT_ABORT, tag);
 		ufshcd_print_evt_hist(hba);
@@ -6800,6 +6811,29 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
 		goto cleanup;
 	}
 
+	/*
+	 * Task abort to the device W-LUN is illegal. When this command
+	 * will fail, due to spec violation, scsi err handling next step
+	 * will be to send LU reset which, again, is a spec violation.
+	 * To avoid these unnecessary/illegal steps, first we clean up
+	 * the lrb taken by this cmd and mark the lrb as in_use, then
+	 * queue the eh_work and bail.
+	 */
+	if (lrbp->lun == UFS_UPIU_UFS_DEVICE_WLUN) {
+		ufshcd_update_evt_hist(hba, UFS_EVT_ABORT, lrbp->lun);
+		spin_lock_irqsave(host->host_lock, flags);
+		if (lrbp->cmd) {
+			__ufshcd_transfer_req_compl(hba, (1UL << tag));
+			__set_bit(tag, &hba->outstanding_reqs);
+			lrbp->in_use = true;
+			hba->force_reset = true;
+			ufshcd_schedule_eh_work(hba);
+		}
+
+		spin_unlock_irqrestore(host->host_lock, flags);
+		goto out;
+	}
+
 	/* Skip task abort in case previous aborts failed and report failure */
 	if (lrbp->req_abort_skip)
 		err = -EIO;
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index 1d4d3f80caa0..08c8a591e6b0 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -193,6 +193,7 @@ struct ufs_pm_lvl_states {
  * @crypto_key_slot: the key slot to use for inline crypto (-1 if none)
  * @data_unit_num: the data unit number for the first block for inline crypto
  * @req_abort_skip: skip request abort task flag
+ * @in_use: indicates that this lrb is still in use
  */
 struct ufshcd_lrb {
 	struct utp_transfer_req_desc *utr_descriptor_ptr;
@@ -222,6 +223,7 @@ struct ufshcd_lrb {
 #endif
 
 	bool req_abort_skip;
+	bool in_use;
 };
 
 /**