linux-kernel - [PATCH v1 6/6] scsi: ufs: Update the fast abort path in ufshcd

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Date:   Wed, 12 May 2021 22:55:19 -0700
From:   Can Guo <cang@...eaurora.org>
To:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, ziqichen@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        cang@...eaurora.org
Cc:     Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v1 6/6] scsi: ufs: Update the fast abort path in ufshcd_abort() for PM requests

If PM requests fail during runtime suspend/resume, RPM framework saves the
error to dev->power.runtime_error. Before the runtime_error gets cleared,
runtime PM on this specific device won't work again, leaving the device
in either suspended or active state permanently.

When task abort happens to a PM request sent during runtime suspend/resume,
even if it can be successfully aborted, RPM framework anyways saves the
(TIMEOUT) error. But we want more and we can do better - let error handling
recover and clear the runtime_error. So, let PM requests take the fast
abort path in ufshcd_abort().

Signed-off-by: Can Guo <cang@...eaurora.org>
---
 drivers/scsi/ufs/ufshcd.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index a6313cf40..2a814e2 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -2643,7 +2643,7 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
 
 	lrbp = &hba->lrb[tag];
 	if (unlikely(lrbp->in_use)) {
-		if (hba->wl_pm_op_in_progress)
+		if (cmd->request->rq_flags & RQF_PM)
 			set_host_byte(cmd, DID_BAD_TARGET);
 		else
 			err = SCSI_MLQUEUE_HOST_BUSY;
@@ -2690,7 +2690,7 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
 		 * err handler blocked for too long. So, just fail the scsi cmd
 		 * sent from PM ops, err handler can recover PM error anyways.
 		 */
-		if (hba->wl_pm_op_in_progress) {
+		if (cmd->request->rq_flags & RQF_PM) {
 			hba->force_reset = true;
 			set_host_byte(cmd, DID_BAD_TARGET);
 			goto out_compl_cmd;
@@ -6959,14 +6959,17 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
 	}
 
 	/*
-	 * 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.
+	 * This fast path guarantees the cmd always gets aborted successfully,
+	 * meanwhile it invokes the error handler. It allows contexts, which
+	 * are blocked by this cmd, to fail fast. It serves multiple purposes:
+	 * #1 To avoid unnecessary/illagal abort attempts to the W-LU.
+	 * #2 To avoid live lock between eh_work and specific contexts, i.e.,
+	 *    suspend/resume and eh_work itself.
+	 * #3 To let eh_work recover runtime PM error in case abort happens
+	 *    to cmds sent from runtime suspend/resume ops.
 	 */
-	if (lrbp->lun == UFS_UPIU_UFS_DEVICE_WLUN) {
+	if (lrbp->lun == UFS_UPIU_UFS_DEVICE_WLUN ||
+	    (cmd->request->rq_flags & RQF_PM)) {
 		ufshcd_update_evt_hist(hba, UFS_EVT_ABORT, lrbp->lun);
 		spin_lock_irqsave(host->host_lock, flags);
 		if (lrbp->cmd) {
-- 
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