On 5/12/21 3:10 PM, James Bottomley wrote:
On Wed, 2021-05-12 at 13:08 -0700, Bart Van Assche wrote:
This patch series renames scsi_get_lba() into scsi_get_pos(). The
name of scsi_get_lba() is confusing since it does not return an LBA
but instead the start offset divided by 512.
OK, I'll bite: given the logical block size for all drives is 512 why
is logical block address not the start offset in bytes divided by 512?
My understanding is that LBA = logical block address = (start offset in
bytes) / (logical block size) and also that the Linux kernel supports
logical block sizes between 512 bytes and 4 KiB. From drivers/scsi/sd.c
(sector_size represents the logical block size):
if (sector_size != 512 &&
sector_size != 1024 &&
sector_size != 2048 &&
sector_size != 4096) {
sd_printk(KERN_NOTICE, sdkp,
"Unsupported sector size %d.\n",
sector_size);
/*
* The user might want to re-format the drive with
* a supported sectorsize. Once this happens, it
* would be relatively trivial to set the thing up.
* For this reason, we leave the thing in the table.
*/
sdkp->capacity = 0;
/*
* set a bogus sector size so the normal read/write
* logic in the block layer will eventually refuse any
* request on this device without tripping over power
* of two sector size assumptions
*/
sector_size = 512;
}
Thanks,
Bart.
