scsi_debug: scale virtual_gb with sector_size properly

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The scsi_debug virtual_gb feature currently assumes that the sector size is always 512 bytes and scales the capacity of virtual_gb based on that assumption.

When passed a different sector size, the capacity of the disk is scaled incorrectly higher than it should be.

For example, modprobe scsi_debug virtual_gb=1 sector_size=4096 results in an 8 GB device.

This patch scales it appropriately. I chose to scale down the sectors-per-GB value and then multiply so that if virtual_gb is changed to allow devices that can max out sector_t, it will just work.

References: https://bugzilla.novell.com/show_bug.cgi?id=535939

- ---

 drivers/scsi/scsi_debug.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

- --- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -154,6 +154,7 @@ static int scsi_debug_virtual_gb = DEF_V
static int scsi_debug_fake_rw = DEF_FAKE_RW;
static int scsi_debug_vpd_use_hostno = DEF_VPD_USE_HOSTNO; static int scsi_debug_sector_size = DEF_SECTOR_SIZE;
+static int scsi_debug_sector_size_bits = ilog2(DEF_SECTOR_SIZE);
static int scsi_debug_dix = DEF_DIX;
static int scsi_debug_dif = DEF_DIF;
static int scsi_debug_guard = DEF_GUARD;
@@ -895,9 +896,11 @@ static int resp_start_stop(struct scsi_c

static sector_t get_sdebug_capacity(void)
{
- - if (scsi_debug_virtual_gb > 0)
- - return 2048 * 1024 * (sector_t)scsi_debug_virtual_gb;
- - else
+ if (scsi_debug_virtual_gb > 0) {
+ sector_t sectors = 2 * 1024 * 1024;
+ sectors >>= (scsi_debug_sector_size_bits - 9);
+ return sectors * (sector_t)scsi_debug_virtual_gb;
+ } else
return sdebug_store_sectors;
}

@@ -2861,6 +2864,7 @@ static int __init scsi_debug_init(void)
case 1024:
case 2048:
case 4096:
+ scsi_debug_sector_size_bits = ilog2(scsi_debug_sector_size);
break;
default:
printk(KERN_ERR "scsi_debug_init: invalid sector_size %d\n",
- --
Jeff Mahoney
SuSE Labs
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