misc/148471: fdisk prompts with negative partition size

[Daniel Feenberg]

>Number:         148471
>Category:       misc
>Synopsis:       fdisk prompts with negative partition size
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Jul 09 15:50:02 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Daniel Feenberg
>Release:        8.0-Release p2
>Organization:
National Bureau of Economic Research
>Environment:
FreeBSD bulk4 8.0-RELEASE-p2 FreeBSD 8.0-RELEASE-p2 #0: Tue Jan  5 16:02:27 UTC 2010     root at i386-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  i386
>Description:
With one of the new 2TB Samsung SATA drives with a 3ware controller (in single drive mode), fdisk reacts in a bizarre manner.

Although it seems to extract the proper drive characteristics:

> parameters extracted from in-core disklabel are:
> cylinders=243151 heads=255 sectors/track=63 (16065 blks/cyl)

When I modify parition 1 and accept all defaults, it suggests a negative value for size:

> Do you want to change it? [n] y
> 
> The static data for the slice 1 has been reinitialized to:
> sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
>     start 63, size 3906220752 (1907334 Meg), flag 80 (active)
>         beg: cyl 0/ head 1/ sector 1;
>         end: cyl 462/ head 254/ sector 63
> Supply a decimal value for "sysid (165=FreeBSD)" [165]
> Supply a decimal value for "start" [63]
> Supply a decimal value for "size" [-388746544]
> Explicitly specify beg/end address ? [n]
> sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
>     start 63, size 3906220752 (1907334 Meg), flag 80 (active)
>         beg: cyl 0/ head 1/ sector 1;
>         end: cyl 462/ head 254/ sector 63
> Are we happy with this entry? [n] y

Notice that the suggested value for size is -388746544 and the suggested end
cylinder is 462 - both of which are implausible and inconsistent.

Here is the info from dmesg about the drive:

>How-To-Repeat:
Obtain 2TB Samsung drive (and possibly 3Ware controller) and run 

  fdisk -i /dev/...

accepting all defaults as one defines a new partion.

Note that this problem did not arise with 300GB drives on the same controller and an earlier version of FreeBSD.
>Fix:
Beyond my knowledge, but I can guess the problem comes from 32 bit integers, and perhaps upgrading to 64 bit FreeBSD would solve the problem for me. However, the bizarre behavior is a bug - if fdisk can't deal with the disk or controller it could say so explicitly.

>Release-Note:
>Audit-Trail:
>Unformatted:
 >a2 at twa0 bus 0 target 2 lun 0
 da2: <AMCC 9500S-8    DISK 2.06> Fixed Direct Access SCSI-3 device