[PATCH] scsi/sd: Fix capacity output to show MB/GB/TB/...

Simon Arlott
2008-08-30T21:03:18Z

The capacity printk'd in bytes is divided by 1000000,
whereas 1048576 would be more consistent with the rest
of the OS and disk-related utilities ('df' etc.).

This change replaces the (sz - (sz/625 - 974))/1950
calculation with a simple right shift to output with
five significant digits the capacity in KB, MB, GB, TB,
PB, or EB. Anything beyond this becomes too large...
---
drivers/scsi/sd.c | 62 ++++++++++++++++++++++++++++++++++------------------
1 files changed, 40 insertions(+), 22 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index e5e7d78..c47a071 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1290,6 +1290,8 @@ sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
struct scsi_sense_hdr sshdr;
int sense_valid = 0;
struct scsi_device *sdp = sdkp->device;
+ unsigned long long orig_capacity, sz;
+ char *units;

repeat:
retries = 3;
@@ -1429,30 +1431,16 @@ got_data:
*/
sector_size = 512;
}
- {
- /*
- * The msdos fs needs to know the hardware sector size
- * So I have created this table. See ll_rw_blk.c
- * Jacques Gelinas (Jacques@solucorp.qc.ca)
- */
- int hard_sector = sector_size;
- sector_t sz = (sdkp->capacity/2) * (hard_sector/256);
- struct request_queue *queue = sdp->request_queue;
- sector_t mb = sz;
-
- blk_queue_hardsect_size(queue, hard_sector);
- /* avoid 64-bit division on 32-bit platforms */
- sector_div(sz, 625);
- mb -= sz - 974;
- sector_div(mb, 1950);

- sd_printk(KERN_NOTICE, sdkp,
- "%llu %d-byte hardware sectors (%llu MB)\n",
- (unsigned long long)sdkp->capacity,
- hard_sector, (unsigned long long)mb);
- }
+ /*
+ * The msdos fs needs to know the hardware sector size
+ * So I have created this table. See ll_rw_blk.c
+ * Jacques Gelinas (Jacques@solucorp.qc.ca)
+ */
+ blk_queue_hardsect_size(sdp->request_queue, sector_size);

/* Rescale capacity to 512-byte units */
+ orig_capacity = sdkp->capacity;
if (sector_size == 4096)
sdkp->capacity <<= 3;
else if (sector_size == 2048)
@@ -1463,6 +1451,36 @@ got_data:
sdkp->capacity >>= 1;

sdkp->device->sector_size = sector_size;
+
+ /* Output device size with at most 5 digits,
+ * this assumes sz is based on a 512-byte
+ * sector size.
+ */
+ sz = sdkp->capacity;
+ if (sz >= (unsigned long long)100000*((unsigned long long)2<<40)) {
+ // 100000PB
+ sz >>= 51;
+ units = "EB";
+ } else if (sz >= (unsigned long long)100000*(2<<30)) { // 100000TB
+ sz >>= 41;
+ units = "PB";
+ } else if (sz >= (unsigned long long)100000*(2<<20)) { // 100000GB
+ sz >>= 31;
+ units = "TB";
+ } else if (sz >= 100000*(2<<10)) { // 100000MB
+ sz >>= 21;
+ units = "GB";
+ } else if (sz >= 100000*2) { // 100000KB
+ sz >>= 11;
+ units = "MB";
+ } else {
+ sz >>= 1;
+ units = "KB";
+ }
+ sd_printk(KERN_NOTICE, sdkp,
+ "%llu %d-byte hardware sectors (%llu %s)\n",
+ (unsigned long long)orig_capacity, sector_size,
+ (unsigned long long)sz, units);
}

/* called with buffer of length 512 */
--
1.5.6.5

--
Simon Arlott