I could swear we had the sizes right but I'll have another look at this.

What raid type did you test this with?

On Sun, Dec 19, 2010 at 02:17:46PM +0100, Andreas Bartelt wrote:
quoted text
> Hello,
> 
> I've noticed that the size of softraid(4) disks is one sector too large.
> 
> In the following description, the native disk is sd4c (which is of type 
> RAID), and the corresponding virtual softraid(4) disk will be sd5. I 
> will assume that sd5 is of discipline CRYPTO, but the problem should be 
> the same for all disciplines.
> 
> The size for sd5 gets eventually stored in struct sr_metadata as 
> sd_meta->ssdi.ssd_size in function sr_crypto_create 
> (dev/softraid_crypto.c). Its value gets initially calculated in function 
> sr_meta_native_probe (dev/softraid.c):
> size = DL_GETPSIZE(&label.d_partitions[part]) - SR_DATA_OFFSET;
> where SR_DATA_OFFSET = 528
> 
> If the size (as shown via disklabel(8)) of the underlying disk sd4c is 
> 'n', the variable 'size' will be calculated as 'n - 528'. However, 
> according to disklabel(8), the resulting softraid(4) disk sd5c will be 
> of size 'n - 528 + 1'. I think this is because function scsi_size in 
> scsi/scsi_base.c returns 'max_addr + 1' where max_addr corresponds to 
> sd_meta->ssdi.ssd_size.
> 
> For example, newfs(8) on /dev/rsd5c tries to write to the last sector of 
> sd5 (first wtfs call in mkfs.c) which is one sector beyond the native 
> disk size of sd4. This gives an error if label sd4c was used as the 
> native device. It results in a kernel panic in case another label of sd4 
> was used as the underlying native device (i.e., sd4a).
> 
> The attached diff fixes the problem for all newly created softraid volumes.
> 
> TODO: fixing the problem for existing softraid(4) volumes would require 
> to update sd_meta->ssdi.ssd_size to the correct size (and probably some 
> other metadata for consistency).
> 
> Best regards
> Andreas
> Index: softraid.c
> ===================================================================
> RCS file: /usr/cvsync/cvs/src/sys/dev/softraid.c,v
> retrieving revision 1.216
> diff -u -r1.216 softraid.c
> --- softraid.c	6 Nov 2010 23:01:56 -0000	1.216
> +++ softraid.c	19 Dec 2010 13:01:14 -0000
> @@ -1386,7 +1386,7 @@
>  		goto unwind;
>  	}
>  
> -	size = DL_GETPSIZE(&label.d_partitions[part]) - SR_DATA_OFFSET;
> +	size = DL_GETPSIZE(&label.d_partitions[part]) - SR_DATA_OFFSET - 1;
>  	if (size <= 0) {
>  		DNPRINTF(SR_D_META, "%s: %s partition too small\n", DEVNAME(sc),
>  		    devname);