Re: [PATCH 09/12] sd: convert to the atomic queue limits API

[John Garry <john.g.garry@oracle.com>]

On 29/05/2024 06:04, Christoph Hellwig wrote:
> Assign all queue limits through a local queue_limits variable and
> queue_limits_commit_update so that we can't race updating them from
> multiple places, and free the queue when updating them so that
> in-progress I/O submissions don't see half-updated limits.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   drivers/scsi/sd.c     | 126 ++++++++++++++++++++++++------------------
>   drivers/scsi/sd.h     |   6 +-
>   drivers/scsi/sd_zbc.c |  15 ++---
>   3 files changed, 84 insertions(+), 63 deletions(-)
> 
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 2d08b69154b995..03e67936b27928 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -101,12 +101,13 @@ MODULE_ALIAS_SCSI_DEVICE(TYPE_ZBC);
>   
>   #define SD_MINORS	16
>   
> -static void sd_config_discard(struct scsi_disk *, unsigned int);
> -static void sd_config_write_same(struct scsi_disk *);
> +static void sd_config_discard(struct scsi_disk *sdkp, struct queue_limits *lim,
> +		unsigned int mode);

Are there any reasons why we keep forward declarations like this? 
AFAICS, this sd_config_discard forward declaration could be removed.

> +static void sd_config_write_same(struct scsi_disk *sdkp,
> +		struct queue_limits *lim);
>   static int  sd_revalidate_disk(struct gendisk *);
>   static void sd_unlock_native_capacity(struct gendisk *disk);
>   static void sd_shutdown(struct device *);
> -static void sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer);
>   static void scsi_disk_release(struct device *cdev);
>   
>   static DEFINE_IDA(sd_index_ida);
> @@ -456,7 +457,8 @@ provisioning_mode_store(struct device *dev, struct device_attribute *attr,
>   {
>   	struct scsi_disk *sdkp = to_scsi_disk(dev);
>   	struct scsi_device *sdp = sdkp->device;
> -	int mode;
> +	struct queue_limits lim;
> +	int mode, err;
>   
>   	if (!capable(CAP_SYS_ADMIN))
>   		return -EACCES;
> @@ -472,8 +474,13 @@ provisioning_mode_store(struct device *dev, struct device_attribute *attr,
>   	if (mode < 0)
>   		return -EINVAL;
>   
> -	sd_config_discard(sdkp, mode);
> -
> +	lim = queue_limits_start_update(sdkp->disk->queue);
> +	sd_config_discard(sdkp, &lim, mode);
> +	blk_mq_freeze_queue(sdkp->disk->queue);
> +	err = queue_limits_commit_update(sdkp->disk->queue, &lim);
> +	blk_mq_unfreeze_queue(sdkp->disk->queue);
> +	if (err)
> +		return err;
>   	return count;
>   }
>   static DEVICE_ATTR_RW(provisioning_mode);
> @@ -556,6 +563,7 @@ max_write_same_blocks_store(struct device *dev, struct device_attribute *attr,
>   {
>   	struct scsi_disk *sdkp = to_scsi_disk(dev);
>   	struct scsi_device *sdp = sdkp->device;
> +	struct queue_limits lim;
>   	unsigned long max;
>   	int err;
>   
> @@ -577,8 +585,13 @@ max_write_same_blocks_store(struct device *dev, struct device_attribute *attr,
>   		sdkp->max_ws_blocks = max;
>   	}
>   
> -	sd_config_write_same(sdkp);
> -
> +	lim = queue_limits_start_update(sdkp->disk->queue);
> +	sd_config_write_same(sdkp, &lim);
> +	blk_mq_freeze_queue(sdkp->disk->queue);
> +	err = queue_limits_commit_update(sdkp->disk->queue, &lim);
> +	blk_mq_unfreeze_queue(sdkp->disk->queue);
> +	if (err)
> +		return err;
>   	return count;
>   }
>   static DEVICE_ATTR_RW(max_write_same_blocks);
> @@ -827,17 +840,15 @@ static void sd_disable_discard(struct scsi_disk *sdkp)
>   	blk_queue_max_discard_sectors(sdkp->disk->queue, 0);
>   }
>   
> -static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
> +static void sd_config_discard(struct scsi_disk *sdkp, struct queue_limits *lim,
> +		unsigned int mode)
>   {
> -	struct request_queue *q = sdkp->disk->queue;
>   	unsigned int logical_block_size = sdkp->device->sector_size;
>   	unsigned int max_blocks = 0;
>   
> -	q->limits.discard_alignment =
> -		sdkp->unmap_alignment * logical_block_size;
> -	q->limits.discard_granularity =
> -		max(sdkp->physical_block_size,
> -		    sdkp->unmap_granularity * logical_block_size);
> +	lim->discard_alignment = sdkp->unmap_alignment * logical_block_size;
> +	lim->discard_granularity = max(sdkp->physical_block_size,
> +			sdkp->unmap_granularity * logical_block_size);
>   	sdkp->provisioning_mode = mode;
>   
>   	switch (mode) {
> @@ -875,7 +886,8 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
>   		break;
>   	}
>   
> -	blk_queue_max_discard_sectors(q, max_blocks * (logical_block_size >> 9));
> +	lim->max_hw_discard_sectors = max_blocks *
> +		(logical_block_size >> SECTOR_SHIFT);
>   }
>   
>   static void *sd_set_special_bvec(struct request *rq, unsigned int data_len)
> @@ -1010,9 +1022,9 @@ static void sd_disable_write_same(struct scsi_disk *sdkp)
>   	blk_queue_max_write_zeroes_sectors(sdkp->disk->queue, 0);
>   }
>   
> -static void sd_config_write_same(struct scsi_disk *sdkp)
> +static void sd_config_write_same(struct scsi_disk *sdkp,
> +		struct queue_limits *lim)
>   {
> -	struct request_queue *q = sdkp->disk->queue;
>   	unsigned int logical_block_size = sdkp->device->sector_size;
>   
>   	if (sdkp->device->no_write_same) {
> @@ -1066,8 +1078,8 @@ static void sd_config_write_same(struct scsi_disk *sdkp)
>   	}
>   
>   out:
> -	blk_queue_max_write_zeroes_sectors(q, sdkp->max_ws_blocks *
> -					 (logical_block_size >> 9));
> +	lim->max_write_zeroes_sectors =
> +		sdkp->max_ws_blocks * (logical_block_size >> 9);

Would it be ok to use SECTOR_SHIFT here? A similar change is made in 
sd_config_discard(), above

>   }
>   
>   static blk_status_t sd_setup_flush_cmnd(struct scsi_cmnd *cmd)
> @@ -2523,7 +2535,7 @@ static void read_capacity_error(struct scsi_disk *sdkp, struct scsi_device *sdp,
>   #define READ_CAPACITY_RETRIES_ON_RESET	10
>   
>   static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
> -						unsigned char *buffer)
> +		struct queue_limits *lim, unsigned char *buffer)
>   {
>   	unsigned char cmd[16];
>   	struct scsi_sense_hdr sshdr;
> @@ -2597,7 +2609,7 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
>   
>   	/* Lowest aligned logical block */
>   	alignment = ((buffer[14] & 0x3f) << 8 | buffer[15]) * sector_size;
> -	blk_queue_alignment_offset(sdp->request_queue, alignment);
> +	lim->alignment_offset = alignment;
>   	if (alignment && sdkp->first_scan)
>   		sd_printk(KERN_NOTICE, sdkp,
>   			  "physical block alignment offset: %u\n", alignment);
> @@ -2608,7 +2620,7 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
>   		if (buffer[14] & 0x40) /* LBPRZ */
>   			sdkp->lbprz = 1;
>   
> -		sd_config_discard(sdkp, SD_LBP_WS16);
> +		sd_config_discard(sdkp, lim, SD_LBP_WS16);
>   	}
>   
>   	sdkp->capacity = lba + 1;
> @@ -2711,13 +2723,14 @@ static int sd_try_rc16_first(struct scsi_device *sdp)
>    * read disk capacity
>    */
>   static void
> -sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
> +sd_read_capacity(struct scsi_disk *sdkp, struct queue_limits *lim,
> +		unsigned char *buffer)
>   {
>   	int sector_size;
>   	struct scsi_device *sdp = sdkp->device;
>   
>   	if (sd_try_rc16_first(sdp)) {
> -		sector_size = read_capacity_16(sdkp, sdp, buffer);
> +		sector_size = read_capacity_16(sdkp, sdp, lim, buffer);
>   		if (sector_size == -EOVERFLOW)
>   			goto got_data;
>   		if (sector_size == -ENODEV)
> @@ -2737,7 +2750,7 @@ sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
>   			int old_sector_size = sector_size;
>   			sd_printk(KERN_NOTICE, sdkp, "Very big device. "
>   					"Trying to use READ CAPACITY(16).\n");
> -			sector_size = read_capacity_16(sdkp, sdp, buffer);
> +			sector_size = read_capacity_16(sdkp, sdp, lim, buffer);
>   			if (sector_size < 0) {
>   				sd_printk(KERN_NOTICE, sdkp,
>   					"Using 0xffffffff as device size\n");
> @@ -2796,9 +2809,8 @@ sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
>   		 */
>   		sector_size = 512;
>   	}
> -	blk_queue_logical_block_size(sdp->request_queue, sector_size);
> -	blk_queue_physical_block_size(sdp->request_queue,
> -				      sdkp->physical_block_size);
> +	lim->logical_block_size = sector_size;
> +	lim->physical_block_size = sdkp->physical_block_size;
>   	sdkp->device->sector_size = sector_size;
>   
>   	if (sdkp->capacity > 0xffffffff)
> @@ -3220,11 +3232,11 @@ static unsigned int sd_discard_mode(struct scsi_disk *sdkp)
>   	return SD_LBP_DISABLE;
>   }
>   
> -/**
> - * sd_read_block_limits - Query disk device for preferred I/O sizes.
> - * @sdkp: disk to query
> +/*
> + * Query disk device for preferred I/O sizes.
>    */
> -static void sd_read_block_limits(struct scsi_disk *sdkp)
> +static void sd_read_block_limits(struct scsi_disk *sdkp,
> +		struct queue_limits *lim)
>   {
>   	struct scsi_vpd *vpd;
>   
> @@ -3258,7 +3270,7 @@ static void sd_read_block_limits(struct scsi_disk *sdkp)
>   			sdkp->unmap_alignment =
>   				get_unaligned_be32(&vpd->data[32]) & ~(1 << 31);
>   
> -		sd_config_discard(sdkp, sd_discard_mode(sdkp));
> +		sd_config_discard(sdkp, lim, sd_discard_mode(sdkp));
>   	}
>   
>    out:
> @@ -3278,10 +3290,10 @@ static void sd_read_block_limits_ext(struct scsi_disk *sdkp)
>   }
>   
>   /**

below is not a kernel doc comment

> - * sd_read_block_characteristics - Query block dev. characteristics
> - * @sdkp: disk to query
> + * Query block dev. characteristics
>    */
> -static void sd_read_block_characteristics(struct scsi_disk *sdkp)
> +static void sd_read_block_characteristics(struct scsi_disk *sdkp,
> +		struct queue_limits *lim)
>   {
>   	struct request_queue *q = sdkp->disk->queue;
>   	struct scsi_vpd *vpd;
> @@ -3307,29 +3319,26 @@ static void sd_read_block_characteristics(struct scsi_disk *sdkp)
>   
>   #ifdef CONFIG_BLK_DEV_ZONED /* sd_probe rejects ZBD devices early otherwise */
>   	if (sdkp->device->type == TYPE_ZBC) {
> -		/*
> -		 * Host-managed.
> -		 */
> -		disk_set_zoned(sdkp->disk);
> +		lim->zoned = true;
>   
>   		/*
>   		 * Per ZBC and ZAC specifications, writes in sequential write
>   		 * required zones of host-managed devices must be aligned to
>   		 * the device physical block size.
>   		 */
> -		blk_queue_zone_write_granularity(q, sdkp->physical_block_size);
> +		lim->zone_write_granularity = sdkp->physical_block_size;
>   	} else {
>   		/*
>   		 * Host-aware devices are treated as conventional.
>   		 */
> -		WARN_ON_ONCE(blk_queue_is_zoned(q));
> +		lim->zoned = false;
>   	}
>   #endif /* CONFIG_BLK_DEV_ZONED */
>   
>   	if (!sdkp->first_scan)
>   		return;
>   
> -	if (blk_queue_is_zoned(q))
> +	if (lim->zoned)
>   		sd_printk(KERN_NOTICE, sdkp, "Host-managed zoned block device\n");
>   	else if (sdkp->zoned == 1)
>   		sd_printk(KERN_NOTICE, sdkp, "Host-aware SMR disk used as regular disk\n");
> @@ -3605,8 +3614,10 @@ static int sd_revalidate_disk(struct gendisk *disk)
>   	struct scsi_device *sdp = sdkp->device;
>   	struct request_queue *q = sdkp->disk->queue;
>   	sector_t old_capacity = sdkp->capacity;
> +	struct queue_limits lim;
>   	unsigned char *buffer;
>   	unsigned int dev_max;
> +	int err;
>   
>   	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp,
>   				      "sd_revalidate_disk\n"));
> @@ -3627,12 +3638,14 @@ static int sd_revalidate_disk(struct gendisk *disk)
>   
>   	sd_spinup_disk(sdkp);
>   
> +	lim = queue_limits_start_update(sdkp->disk->queue);
> +
>   	/*
>   	 * Without media there is no reason to ask; moreover, some devices
>   	 * react badly if we do.
>   	 */
>   	if (sdkp->media_present) {
> -		sd_read_capacity(sdkp, buffer);
> +		sd_read_capacity(sdkp, &lim, buffer);
>   		/*
>   		 * Some USB/UAS devices return generic values for mode pages
>   		 * until the media has been accessed. Trigger a READ operation
> @@ -3651,10 +3664,10 @@ static int sd_revalidate_disk(struct gendisk *disk)
>   
>   		if (scsi_device_supports_vpd(sdp)) {
>   			sd_read_block_provisioning(sdkp);
> -			sd_read_block_limits(sdkp);
> +			sd_read_block_limits(sdkp, &lim);
>   			sd_read_block_limits_ext(sdkp);
> -			sd_read_block_characteristics(sdkp);
> -			sd_zbc_read_zones(sdkp, buffer);
> +			sd_read_block_characteristics(sdkp, &lim);
> +			sd_zbc_read_zones(sdkp, &lim, buffer);
>   			sd_read_cpr(sdkp);
>   		}
>   
> @@ -3683,28 +3696,33 @@ static int sd_revalidate_disk(struct gendisk *disk)
>   	q->limits.max_dev_sectors = logical_to_sectors(sdp, dev_max);


is setting q->limits.max_dev_sectors directly proper?

>   
>   	if (sd_validate_min_xfer_size(sdkp))
> -		blk_queue_io_min(sdkp->disk->queue,
> -				 logical_to_bytes(sdp, sdkp->min_xfer_blocks));
> +		lim.io_min = logical_to_bytes(sdp, sdkp->min_xfer_blocks);
>   	else
> -		blk_queue_io_min(sdkp->disk->queue, 0);
> +		lim.io_min = 0;
>   
>   	/*
>   	 * Limit default to SCSI host optimal sector limit if set. There may be
>   	 * an impact on performance for when the size of a request exceeds this
>   	 * host limit.
>   	 */
> -	q->limits.io_opt = sdp->host->opt_sectors << SECTOR_SHIFT;
> +	lim.io_opt = sdp->host->opt_sectors << SECTOR_SHIFT;
>   	if (sd_validate_opt_xfer_size(sdkp, dev_max)) {
> -		q->limits.io_opt = min_not_zero(q->limits.io_opt,
> +		lim.io_opt = min_not_zero(lim.io_opt,
>   				logical_to_bytes(sdp, sdkp->opt_xfer_blocks));
>   	}
>   
>   	sdkp->first_scan = 0;
>   
>   	set_capacity_and_notify(disk, logical_to_sectors(sdp, sdkp->capacity));
> -	sd_config_write_same(sdkp);
> +	sd_config_write_same(sdkp, &lim);
>   	kfree(buffer);
>