Re: [PATCH 2/3] ide-cd: cleanup cdrom_decode_status

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Thursday 02 April 2009, Borislav Petkov wrote:
> - have (almost) equal handling of commands based solely on sense_key

I'm having a VERY hard time trying to review this patch because at
the same time that codepaths were merged if()s were replaced by switch()
which in turn resulted in change of intendation... on top of that
the patch description is very vague about this part of the changes...

We're dealing with tricky error recovery code here and it is very easy
for subtle bugs to slip in => it is very important to have the changes
easily reviewable by as many people as possible.

Sorry but this part is "almost" good and needs to be re-done.

> - carve out an ide_cd_breathe()-helper for fs write requests

This may be as well done in a pre-patch to not hold this change back
and make the main change more readable.

> - make code more readable
> 
> There should be no functional change resulting from this patch.
> 
> Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
> ---
>  drivers/ide/ide-cd.c |  238 ++++++++++++++++++++++---------------------------
>  1 files changed, 107 insertions(+), 131 deletions(-)
> 
> diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
> index a4afd90..8387dbf 100644
> --- a/drivers/ide/ide-cd.c
> +++ b/drivers/ide/ide-cd.c
> @@ -266,6 +266,38 @@ static void ide_cd_complete_failed_rq(ide_drive_t *drive, struct request *rq)
>  }
>  
>  /*
> + * Allow the drive 5 seconds to recover; some devices will return NOT_READY
> + * while flushing data from cache
> + */
> +static int ide_cd_breathe(ide_drive_t *drive, struct request *rq)
> +{
> +
> +	struct cdrom_info *info = drive->driver_data;
> +
> +	if (!rq->errors)
> +		info->write_timeout = jiffies +	ATAPI_WAIT_WRITE_BUSY;
> +
> +	rq->errors = 1;
> +
> +	if (time_after(jiffies, info->write_timeout))
> +		return 1;
> +	else {
> +		struct request_queue *q = drive->queue;
> +		unsigned long flags;
> +
> +		/*
> +		 * take a breather relying on the unplug timer to kick us again
> +		 */
> +
> +		spin_lock_irqsave(q->queue_lock, flags);
> +		blk_plug_device(q);
> +		spin_unlock_irqrestore(q->queue_lock, flags);
> +
> +		return 0;
> +	}
> +}
> +
> +/*
>   * Returns:
>   * 0: if the request should be continued.
>   * 1: if the request will be going through error recovery.
> @@ -275,14 +307,15 @@ static int cdrom_decode_status(ide_drive_t *drive, u8 stat)
>  {
>  	ide_hwif_t *hwif = drive->hwif;
>  	struct request *rq = hwif->rq;
> -	int err, sense_key;
> +	int err, sense_key, do_end_request;
>  
>  	/* get the IDE error register */
>  	err = ide_read_error(drive);
>  	sense_key = err >> 4;
>  
> -	ide_debug_log(IDE_DBG_RQ, "cmd[0]: 0x%x, rq->cmd_type: 0x%x, err: 0x%x",
> -				  rq->cmd[0], rq->cmd_type, err);
> +	ide_debug_log(IDE_DBG_RQ, "cmd: 0x%x, rq->cmd_type: 0x%x, err: 0x%x, "
> +				  "stat 0x%x",
> +				  rq->cmd[0], rq->cmd_type, err, stat);
>  
>  	if (blk_sense_request(rq)) {
>  		/*
> @@ -292,151 +325,93 @@ static int cdrom_decode_status(ide_drive_t *drive, u8 stat)
>  		 */
>  		rq->cmd_flags |= REQ_FAILED;
>  		return 2;
> -	} else if (blk_pc_request(rq) || rq->cmd_type == REQ_TYPE_ATA_PC) {
> -		/* All other functions, except for READ. */
> +	}
>  
> -		/*
> -		 * if we have an error, pass back CHECK_CONDITION as the
> -		 * scsi status byte
> -		 */
> -		if (blk_pc_request(rq) && !rq->errors)
> -			rq->errors = SAM_STAT_CHECK_CONDITION;
> +	/* if we got an error, pass CHECK_CONDITION as the scsi status byte */
> +	if (blk_pc_request(rq) && !rq->errors)
> +		rq->errors = SAM_STAT_CHECK_CONDITION;
>  
> -		/* check for tray open */
> -		if (sense_key == NOT_READY) {
> -			cdrom_saw_media_change(drive);
> -		} else if (sense_key == UNIT_ATTENTION) {
> -			/* check for media change */
> +	if (blk_noretry_request(rq))
> +			do_end_request = 1;
> +
> +	switch (sense_key) {
> +	case NOT_READY:
> +		if (blk_fs_request(rq) && (rq_data_dir(rq) == WRITE)) {
> +			if (!ide_cd_breathe(drive, rq))
> +				return 1;
> +		} else {
>  			cdrom_saw_media_change(drive);
> -			return 0;
> -		} else if (sense_key == ILLEGAL_REQUEST &&
> -			   rq->cmd[0] == GPCMD_START_STOP_UNIT) {
> -			/*
> -			 * Don't print error message for this condition--
> -			 * SFF8090i indicates that 5/24/00 is the correct
> -			 * response to a request to close the tray if the
> -			 * drive doesn't have that capability.
> -			 * cdrom_log_sense() knows this!
> -			 */
> -		} else if (!(rq->cmd_flags & REQ_QUIET)) {
> -			/* otherwise, print an error */
> -			ide_dump_status(drive, "packet command error", stat);
> +			printk(KERN_ERR PFX "%s: tray open\n", drive->name);
>  		}
> +		do_end_request = 1;
> +		break;
>  
> -		rq->cmd_flags |= REQ_FAILED;
> +	case UNIT_ATTENTION:
> +		cdrom_saw_media_change(drive);
> +		if (blk_pc_request(rq) || rq->cmd_type == REQ_TYPE_ATA_PC)
> +			return 0;
> +		break;
>  
> +	case ILLEGAL_REQUEST:
> +	case DATA_PROTECT:
>  		/*
> -		 * instead of playing games with moving completions around,
> -		 * remove failed request completely and end it when the
> -		 * request sense has completed
> +		 * Don't print error message for this condition since SFF8090i
> +		 * indicates that 5/24/00 is the correct response to a request
> +		 * to close the tray if the drive doesn't have that capability.
> +		 *
> +		 * cdrom_log_sense() knows this!
>  		 */
> -		goto end_request;
> -
> -	} else if (blk_fs_request(rq)) {
> -		int do_end_request = 0;
> -
> -		/* handle errors from READ and WRITE requests */
> -
> -		if (blk_noretry_request(rq))
> +		if (rq->cmd[0] != GPCMD_START_STOP_UNIT) {
> +			ide_dump_status(drive, "command error", stat);
>  			do_end_request = 1;
> +		}
> +		break;
>  
> -		if (sense_key == NOT_READY) {
> -			/* tray open */
> -			if (rq_data_dir(rq) == READ) {
> -				cdrom_saw_media_change(drive);
> -
> -				/* fail the request */
> -				printk(KERN_ERR PFX "%s: tray open\n",
> -						drive->name);
> -				do_end_request = 1;
> -			} else {
> -				struct cdrom_info *info = drive->driver_data;
> +	case MEDIUM_ERROR:
> +		/*
> +		 * No point in re-trying a zillion times on a bad sector. If we
> +		 * got here the error is not correctable.
> +		 */
> +		ide_dump_status(drive, "media error (bad sector)", stat);
> +		do_end_request = 1;
> +		break;
>  
> -				/*
> -				 * Allow the drive 5 seconds to recover, some
> -				 * devices will return this error while flushing
> -				 * data from cache.
> -				 */
> -				if (!rq->errors)
> -					info->write_timeout = jiffies +
> -							ATAPI_WAIT_WRITE_BUSY;
> -				rq->errors = 1;
> -				if (time_after(jiffies, info->write_timeout))
> -					do_end_request = 1;
> -				else {
> -					struct request_queue *q = drive->queue;
> -					unsigned long flags;
> -
> -					/*
> -					 * take a breather relying on the unplug
> -					 * timer to kick us again
> -					 */
> -					spin_lock_irqsave(q->queue_lock, flags);
> -					blk_plug_device(q);
> -					spin_unlock_irqrestore(q->queue_lock, flags);
> -
> -					return 1;
> -				}
> -			}
> -		} else if (sense_key == UNIT_ATTENTION) {
> -			/* media change */
> -			cdrom_saw_media_change(drive);
> +	case BLANK_CHECK:
> +		/* disk appears blank ?? */
> +		ide_dump_status(drive, "media error (blank)", stat);
> +		do_end_request = 1;
> +		break;
>  
> -			/*
> -			 * Arrange to retry the request but be sure to give up
> -			 * if we've retried too many times.
> -			 */
> -			if (++rq->errors > ERROR_MAX)
> -				do_end_request = 1;
> -		} else if (sense_key == ILLEGAL_REQUEST ||
> -			   sense_key == DATA_PROTECT) {
> -			/*
> -			 * No point in retrying after an illegal request or data
> -			 * protect error.
> -			 */
> -			ide_dump_status(drive, "command error", stat);
> -			do_end_request = 1;
> -		} else if (sense_key == MEDIUM_ERROR) {
> -			/*
> -			 * No point in re-trying a zillion times on a bad
> -			 * sector. If we got here the error is not correctable.
> -			 */
> -			ide_dump_status(drive, "media error (bad sector)",
> -					stat);
> -			do_end_request = 1;
> -		} else if (sense_key == BLANK_CHECK) {
> -			/* disk appears blank ?? */
> -			ide_dump_status(drive, "media error (blank)", stat);
> -			do_end_request = 1;
> -		} else if ((err & ~ATA_ABORTED) != 0) {
> +	default:
> +		if (err & ~ATA_ABORTED) {
>  			/* go to the default handler for other errors */
>  			ide_error(drive, "cdrom_decode_status", stat);
>  			return 1;
> -		} else if ((++rq->errors > ERROR_MAX)) {
> -			/* we've racked up too many retries, abort */
> -			do_end_request = 1;
>  		}
>  
> -		/*
> -		 * End a request through request sense analysis when we have
> -		 * sense data. We need this in order to perform end of media
> -		 * processing.
> -		 */
> -		if (do_end_request)
> -			goto end_request;
> +		if (!(rq->cmd_flags & REQ_QUIET)) {
> +			ide_dump_status(drive, "command error", stat);
> +			blk_dump_rq_flags(rq, PFX "failing rq");
> +		}
> +		do_end_request = 1;
> +		break;
> +	}
>  
> -		/*
> -		 * If we got a CHECK_CONDITION status, queue
> -		 * a request sense command.
> -		 */
> -		if (stat & ATA_ERR)
> -			cdrom_queue_request_sense(drive, NULL, NULL);
> -		return 1;
> -	} else {
> -		blk_dump_rq_flags(rq, PFX "bad rq");
> -		return 2;
> +	/* we've racked up too many retries, abort */
> +	if (++rq->errors > ERROR_MAX)
> +		do_end_request = 1;
> +
> +	if (do_end_request) {
> +		rq->cmd_flags |= REQ_FAILED;
> +		goto end_request;
>  	}
>  
> +	/* If we got a CHECK_CONDITION status, queue a request sense command. */
> +	if (stat & ATA_ERR)
> +		cdrom_queue_request_sense(drive, NULL, NULL);
> +
> +	return 1;
> +
>  end_request:
>  	if (stat & ATA_ERR) {
>  		struct request_queue *q = drive->queue;
> @@ -614,14 +589,15 @@ static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
>  	struct request *rq = hwif->rq;
>  	ide_expiry_t *expiry = NULL;
>  	int dma_error = 0, dma, thislen, uptodate = 0;
> -	int write = (rq_data_dir(rq) == WRITE) ? 1 : 0, rc, nsectors;
> +	int write, uninitialized_var(rc), nsectors;

Why is uninitialized_var() here now?

>  	int sense = blk_sense_request(rq);
>  	unsigned int timeout;
>  	u16 len;
>  	u8 ireason, stat;
>  
> -	ide_debug_log(IDE_DBG_PC, "cmd[0]: 0x%x, write: 0x%x",
> -				  rq->cmd[0], write);
> +	write = (rq_data_dir(rq) == WRITE) ? 1 : 0;
> 
> +	ide_debug_log(IDE_DBG_PC, "cmd: 0x%x, write: 0x%x", rq->cmd[0], write);
>  
>  	/* check for errors */
>  	dma = drive->dma;