[PATCH] scsi: sd: Revert "Rework asynchronous resume support"

* [PATCH] scsi: sd: Revert "Rework asynchronous resume support"
@ 2022-08-16 17:26 Bart Van Assche
  2022-08-16 18:00 ` John Garry
                   ` (2 more replies)
  0 siblings, 3 replies; 12+ messages in thread
From: Bart Van Assche @ 2022-08-16 17:26 UTC (permalink / raw)
  To: Martin K . Petersen
  Cc: linux-scsi, Bart Van Assche, Damien Le Moal, Hannes Reinecke,
	Geert Uytterhoeven, gzhqyz, James E.J. Bottomley

Although patch "Rework asynchronous resume support" eliminates the delay
for some ATA disks after resume, it causes resume of ATA disks to fail
on other setups. See also:
* "Resume process hangs for 5-6 seconds starting sometime in 5.16"
  (https://bugzilla.kernel.org/show_bug.cgi?id=215880).
* Geert's regression report
  (https://lore.kernel.org/linux-scsi/alpine.DEB.2.22.394.2207191125130.1006766@ramsan.of.borg/).

This is what I understand about this issue:
* During resume, ata_port_pm_resume() starts the SCSI error handler.
  This changes the SCSI host state into SHOST_RECOVERY and causes
  scsi_queue_rq() to return BLK_STS_RESOURCE.
* sd_resume() calls sd_start_stop_device() for ATA devices. That
  function in turn calls sd_submit_start() which tries to submit a START
  STOP UNIT command. That command can only be submitted after the SCSI
  error handler has changed the SCSI host state back to SHOST_RUNNING.
* The SCSI error handler runs on its own thread and calls
  schedule_work(&(ap->scsi_rescan_task)). That causes
  ata_scsi_dev_rescan() to be called from the context of a kernel
  workqueue. That call hangs in blk_mq_get_tag(). I'm not sure why -
  maybe because all available tags have been allocated by
  sd_submit_start() calls (this is a guess).

Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: gzhqyz@gmail.com
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reported-by: gzhqyz@gmail.com
Fixes: 88f1669019bd ("scsi: sd: Rework asynchronous resume support"; v6.0-rc1~114^2~68)
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/sd.c | 84 ++++++++++-------------------------------------
 drivers/scsi/sd.h |  5 ---
 2 files changed, 18 insertions(+), 71 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 8f79fa6318fe..eb76ba055021 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -103,7 +103,6 @@ static void sd_config_discard(struct scsi_disk *, unsigned int);
 static void sd_config_write_same(struct scsi_disk *);
 static int  sd_revalidate_disk(struct gendisk *);
 static void sd_unlock_native_capacity(struct gendisk *disk);
-static void sd_start_done_work(struct work_struct *work);
 static int  sd_probe(struct device *);
 static int  sd_remove(struct device *);
 static void sd_shutdown(struct device *);
@@ -3471,7 +3470,6 @@ static int sd_probe(struct device *dev)
 	sdkp->max_retries = SD_MAX_RETRIES;
 	atomic_set(&sdkp->openers, 0);
 	atomic_set(&sdkp->device->ioerr_cnt, 0);
-	INIT_WORK(&sdkp->start_done_work, sd_start_done_work);
 
 	if (!sdp->request_queue->rq_timeout) {
 		if (sdp->type != TYPE_MOD)
@@ -3594,69 +3592,12 @@ static void scsi_disk_release(struct device *dev)
 	kfree(sdkp);
 }
 
-/* Process sense data after a START command finished. */
-static void sd_start_done_work(struct work_struct *work)
-{
-	struct scsi_disk *sdkp = container_of(work, typeof(*sdkp),
-					      start_done_work);
-	struct scsi_sense_hdr sshdr;
-	int res = sdkp->start_result;
-
-	if (res == 0)
-		return;
-
-	sd_print_result(sdkp, "Start/Stop Unit failed", res);
-
-	if (res < 0)
-		return;
-
-	if (scsi_normalize_sense(sdkp->start_sense_buffer,
-				 sdkp->start_sense_len, &sshdr))
-		sd_print_sense_hdr(sdkp, &sshdr);
-}
-
-/* A START command finished. May be called from interrupt context. */
-static void sd_start_done(struct request *req, blk_status_t status)
-{
-	const struct scsi_cmnd *scmd = blk_mq_rq_to_pdu(req);
-	struct scsi_disk *sdkp = scsi_disk(req->q->disk);
-
-	sdkp->start_result = scmd->result;
-	WARN_ON_ONCE(scmd->sense_len > SCSI_SENSE_BUFFERSIZE);
-	sdkp->start_sense_len = scmd->sense_len;
-	memcpy(sdkp->start_sense_buffer, scmd->sense_buffer,
-	       ARRAY_SIZE(sdkp->start_sense_buffer));
-	WARN_ON_ONCE(!schedule_work(&sdkp->start_done_work));
-}
-
-/* Submit a START command asynchronously. */
-static int sd_submit_start(struct scsi_disk *sdkp, u8 cmd[], u8 cmd_len)
-{
-	struct scsi_device *sdev = sdkp->device;
-	struct request_queue *q = sdev->request_queue;
-	struct request *req;
-	struct scsi_cmnd *scmd;
-
-	req = scsi_alloc_request(q, REQ_OP_DRV_IN, BLK_MQ_REQ_PM);
-	if (IS_ERR(req))
-		return PTR_ERR(req);
-
-	scmd = blk_mq_rq_to_pdu(req);
-	scmd->cmd_len = cmd_len;
-	memcpy(scmd->cmnd, cmd, cmd_len);
-	scmd->allowed = sdkp->max_retries;
-	req->timeout = SD_TIMEOUT;
-	req->rq_flags |= RQF_PM | RQF_QUIET;
-	req->end_io = sd_start_done;
-	blk_execute_rq_nowait(req, /*at_head=*/true);
-
-	return 0;
-}
-
 static int sd_start_stop_device(struct scsi_disk *sdkp, int start)
 {
 	unsigned char cmd[6] = { START_STOP };	/* START_VALID */
+	struct scsi_sense_hdr sshdr;
 	struct scsi_device *sdp = sdkp->device;
+	int res;
 
 	if (start)
 		cmd[4] |= 1;	/* START */
@@ -3667,10 +3608,23 @@ static int sd_start_stop_device(struct scsi_disk *sdkp, int start)
 	if (!scsi_device_online(sdp))
 		return -ENODEV;
 
-	/* Wait until processing of sense data has finished. */
-	flush_work(&sdkp->start_done_work);
+	res = scsi_execute(sdp, cmd, DMA_NONE, NULL, 0, NULL, &sshdr,
+			SD_TIMEOUT, sdkp->max_retries, 0, RQF_PM, NULL);
+	if (res) {
+		sd_print_result(sdkp, "Start/Stop Unit failed", res);
+		if (res > 0 && scsi_sense_valid(&sshdr)) {
+			sd_print_sense_hdr(sdkp, &sshdr);
+			/* 0x3a is medium not present */
+			if (sshdr.asc == 0x3a)
+				res = 0;
+		}
+	}
 
-	return sd_submit_start(sdkp, cmd, sizeof(cmd));
+	/* SCSI error codes must not go to the generic layer */
+	if (res)
+		return -EIO;
+
+	return 0;
 }
 
 /*
@@ -3697,8 +3651,6 @@ static void sd_shutdown(struct device *dev)
 		sd_printk(KERN_NOTICE, sdkp, "Stopping disk\n");
 		sd_start_stop_device(sdkp, 0);
 	}
-
-	flush_work(&sdkp->start_done_work);
 }
 
 static int sd_suspend_common(struct device *dev, bool ignore_stop_errors)
diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index b89187761d61..5eea762f84d1 100644
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -150,11 +150,6 @@ struct scsi_disk {
 	unsigned	urswrz : 1;
 	unsigned	security : 1;
 	unsigned	ignore_medium_access_errors : 1;
-
-	int		start_result;
-	u32		start_sense_len;
-	u8		start_sense_buffer[SCSI_SENSE_BUFFERSIZE];
-	struct work_struct start_done_work;
 };
 #define to_scsi_disk(obj) container_of(obj, struct scsi_disk, disk_dev)
 

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