Re: [PATCH] sd: fixup capacity calculation for 4k drives

[Lee Duncan <lduncan@suse.com>]

On 03/29/2016 01:06 AM, Hannes Reinecke wrote:
> in sd_read_capacity() the sdkp->capacity field changes its meaning:
> after the call to read_capacity_XX() it carries the _unscaled_ values,
> making the comparison between the original value and the new value
> always false for drives with a sector size != 512.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---
>  drivers/scsi/sd.c | 69 +++++++++++++++++++++++++++++++------------------------
>  1 file changed, 39 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 5a5457a..0afe113 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -2046,7 +2046,7 @@ 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)
> +			    unsigned char *buffer, u64 *capacity)
>  {
>  	unsigned char cmd[16];
>  	struct scsi_sense_hdr sshdr;
> @@ -2054,8 +2054,8 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
>  	int the_result;
>  	int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
>  	unsigned int alignment;
> -	unsigned long long lba;
> -	unsigned sector_size;
> +	u64 lba;
> +	u32 sector_size;
>  
>  	if (sdp->no_read_capacity_16)
>  		return -EINVAL;
> @@ -2114,7 +2114,7 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
>  		sd_printk(KERN_ERR, sdkp, "Too big for this kernel. Use a "
>  			"kernel compiled with support for large block "
>  			"devices.\n");
> -		sdkp->capacity = 0;
> +		*capacity = 0;
>  		return -EOVERFLOW;
>  	}
>  
> @@ -2137,20 +2137,20 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
>  		sd_config_discard(sdkp, SD_LBP_WS16);
>  	}
>  
> -	sdkp->capacity = lba + 1;
> +	*capacity = lba + 1;
>  	return sector_size;
>  }
>  
>  static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
> -						unsigned char *buffer)
> +			    unsigned char *buffer, u64 *capacity)
>  {
>  	unsigned char cmd[16];
>  	struct scsi_sense_hdr sshdr;
>  	int sense_valid = 0;
>  	int the_result;
>  	int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
> -	sector_t lba;
> -	unsigned sector_size;
> +	u32 lba;
> +	u32 sector_size;
>  
>  	do {
>  		cmd[0] = READ_CAPACITY;
> @@ -2191,7 +2191,7 @@ static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
>  		/* Some buggy (usb cardreader) devices return an lba of
>  		   0xffffffff when the want to report a size of 0 (with
>  		   which they really mean no media is present) */
> -		sdkp->capacity = 0;
> +		*capacity = 0;
>  		sdkp->physical_block_size = sector_size;
>  		return sector_size;
>  	}
> @@ -2200,11 +2200,11 @@ static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
>  		sd_printk(KERN_ERR, sdkp, "Too big for this kernel. Use a "
>  			"kernel compiled with support for large block "
>  			"devices.\n");
> -		sdkp->capacity = 0;
> +		*capacity = 0;
>  		return -EOVERFLOW;
>  	}
>  
> -	sdkp->capacity = lba + 1;
> +	*capacity = (u64)lba + 1;
>  	sdkp->physical_block_size = sector_size;
>  	return sector_size;
>  }
> @@ -2230,34 +2230,38 @@ sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
>  {
>  	int sector_size;
>  	struct scsi_device *sdp = sdkp->device;
> -	sector_t old_capacity = sdkp->capacity;
> +	u64 old_capacity = sdkp->capacity, new_capacity;
>  
>  	if (sd_try_rc16_first(sdp)) {
> -		sector_size = read_capacity_16(sdkp, sdp, buffer);
> +		sector_size = read_capacity_16(sdkp, sdp, buffer,
> +					       &new_capacity);
>  		if (sector_size == -EOVERFLOW)
>  			goto got_data;
>  		if (sector_size == -ENODEV)
>  			return;
>  		if (sector_size < 0)
> -			sector_size = read_capacity_10(sdkp, sdp, buffer);
> +			sector_size = read_capacity_10(sdkp, sdp, buffer,
> +						       &new_capacity);
>  		if (sector_size < 0)
>  			return;
>  	} else {
> -		sector_size = read_capacity_10(sdkp, sdp, buffer);
> +		sector_size = read_capacity_10(sdkp, sdp, buffer,
> +					       &new_capacity);
>  		if (sector_size == -EOVERFLOW)
>  			goto got_data;
>  		if (sector_size < 0)
>  			return;
>  		if ((sizeof(sdkp->capacity) > 4) &&
> -		    (sdkp->capacity > 0xffffffffULL)) {
> +		    (new_capacity > 0xffffffffULL)) {
>  			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, buffer,
> +						       &new_capacity);
>  			if (sector_size < 0) {
>  				sd_printk(KERN_NOTICE, sdkp,
>  					"Using 0xffffffff as device size\n");
> -				sdkp->capacity = 1 + (sector_t) 0xffffffff;
> +				new_capacity = 1 + (u64) 0xffffffff;
>  				sector_size = old_sector_size;
>  				goto got_data;
>  			}
> @@ -2275,11 +2279,11 @@ sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
>  	 * the capacity.
>  	 */
>  	if (sdp->fix_capacity ||
> -	    (sdp->guess_capacity && (sdkp->capacity & 0x01))) {
> +	    (sdp->guess_capacity && (new_capacity & 0x01))) {
>  		sd_printk(KERN_INFO, sdkp, "Adjusting the sector count "
>  				"from its reported value: %llu\n",
> -				(unsigned long long) sdkp->capacity);
> -		--sdkp->capacity;
> +				(unsigned long long) new_capacity);
> +		--new_capacity;
>  	}
>  
>  got_data:
> @@ -2301,7 +2305,7 @@ got_data:
>  		 * would be relatively trivial to set the thing up.
>  		 * For this reason, we leave the thing in the table.
>  		 */
> -		sdkp->capacity = 0;
> +		new_capacity = 0;
>  		/*
>  		 * set a bogus sector size so the normal read/write
>  		 * logic in the block layer will eventually refuse any
> @@ -2312,6 +2316,19 @@ got_data:
>  	}
>  	blk_queue_logical_block_size(sdp->request_queue, sector_size);
>  
> +	/*
> +	 * Note: up to this point new_capacity carries the
> +	 * _unscaled_ capacity. So rescale capacity to 512-byte units.
> +	 */
> +	if (sector_size == 4096)
> +		sdkp->capacity = new_capacity << 3;
> +	else if (sector_size == 2048)
> +		sdkp->capacity = new_capacity << 2;
> +	else if (sector_size == 1024)
> +		sdkp->capacity = new_capacity << 1;
> +	else
> +		sdkp->capacity = new_capacity;
> +
>  	{
>  		char cap_str_2[10], cap_str_10[10];
>  
> @@ -2337,14 +2354,6 @@ got_data:
>  	if (sdkp->capacity > 0xffffffff)
>  		sdp->use_16_for_rw = 1;
>  
> -	/* Rescale capacity to 512-byte units */
> -	if (sector_size == 4096)
> -		sdkp->capacity <<= 3;
> -	else if (sector_size == 2048)
> -		sdkp->capacity <<= 2;
> -	else if (sector_size == 1024)
> -		sdkp->capacity <<= 1;
> -
>  	blk_queue_physical_block_size(sdp->request_queue,
>  				      sdkp->physical_block_size);
>  	sdkp->device->sector_size = sector_size;
> 

Reviewed-by: Lee Duncan <lduncan@suse.com>