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

[Vlastimil Babka <vbabka@suse.cz>]

On 8/16/22 19:26, Bart Van Assche wrote:
> 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>

Reported-and-tested-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  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)
>