Re: [PATCH 3/4] scsi: increase upper limit for max_sectors

[Christoph Hellwig <hch@infradead.org>]

On Sun, May 25, 2014 at 09:43:35PM +0900, Akinobu Mita wrote:
> max_sectors in struct Scsi_Host specifies maximum number of sectors
> allowed in a single SCSI command.  The data type of max_sectors is
> unsigned short, so the maximum transfer length per SCSI command is
> limited to less than 256MB in 4096-bytes sector size. (0xffff * 4096)
> 
> This commit increases the SCSI mid level's limitation for max_sectors
> upto the block layer's limitation for max_hw_sectors by extending the
> data type of max_sectors in struct Scsi_Host and scsi_host_template,
> so that SCSI lower level drivers can specify more than 0xffff.
> 
> This change requires the scsi disk (sd) driver to handle the requests
> whose transfer length is more than 0xffff with READ_16 or WRITE_16.
> Also, this needs to prevent SG_GET_RESERVED_SIZE and SG_SET_RESERVED_SIZE
> ioctls for the scsi generic (sg) driver from integer overflow when
> converting max_sectors to bytes.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>

Looks good, but I think this should be three patches, one for the ioctl
in sg, one for the command selection in sd, and one to change the field
with in the scsi core.