On Thu, 20 Oct 2005 19:04:47 -0400 Bill Davidsen wrote: > Randy.Dunlap wrote: > > On Thu, 20 Oct 2005, Dale Blount wrote: > > > > > >>On Wed, 2005-10-19 at 22:09 -0700, Randy.Dunlap wrote: > >> > >>>On Mon, 17 Oct 2005 15:24:04 -0400 Dale Blount wrote: > >>> > >>> > >>>>Hello, > >>>> > >>>>I just added 2 external 1TB+ scsi devices to my i686 linux server > >>>>running 2.6.13.4 connected to external LSI MPT card. fdisk and df both > >>>>show the sizes correctly (see below), but I'm worried that dmesg reports > >>>>them incorrectly. > >>>> > >>>>SCSI device sda: 2460934144 512-byte hdwr sectors (160487 MB) > >>>>SCSI device sdb: 3790438400 512-byte hdwr sectors (841193 MB) > >>>> > >>>>I don't think it's as simple as a variable overflow because both > >>>>sdkp->capacity and mb look to be cast as unsigned long longs. I know a > >>>>workaround is to present less data per LUN, but I'd like to use it as > >>>>it's setup currently if possible. Is this just printing incorrectly or > >>>>will I run into trouble when the device gets more full? > >>> > >>>The casts to (unsigned long long) just fix the printk() args to match > >>>the format strings (and eliminate warnings). > >>> > >>>Looks to me like sdkp->capacity is correct. The <mb> value looks > >>>way off. Since it's just printed here for user info, I don't see > >>>how it can be a problem later on. > >>> > >> > >>That's what I was hoping, but I didn't know for sure. I figured I'd > >>better ask to make sure my data wouldn't get truncated when the disk got > >>fuller. Between my first post and now, I've tested it by filling the > >>drive with data and testing the md5sums for each file and it seems to > >>work. Other than the odd MB size reported, it seems to work just fine. > >> > >> > >>>I don't see the error just yet. Are there any other SCSI device- > >>>related messages near these? And just to confirm, but you must > >>>have CONFIG_LBD (Large Block Device) enabled, right? > >>> > >> > >>No, there are no other related messages near these other than the > >>standard vendor/versions. I did not enable CONFIG_LBD since the help > >>says "bigger than 2TB", and I partitioned the storage system to present > >>disks smaller than that. > > > > > > I guessed at CONFIG_LBD=y last night. Today I did the arithmetic > > with CONFIG_LBD=n... and found the overflow. > > > > In drivers/scsi/sd.c, approx. line #1260: > > > > sector_t sz = sdkp->capacity * (hard_sector/256); > > > > sz is 32 bits. > > capacity is 32 bits with a value of 2,460,934,144 == 0x92ae_e000. > > Then we multiply that by 2 (512 / 256)... and it overflows. > > Should be hex 1_255d_c000, but we drop the '1'. > > The rest of the calculation (with this new value) does result > > in the 160487 MB, matching your log message. > > > > I think that you can fix it (patch it) by changing that line > > to make 'sz' be type 'u64' for now. > > > > u64 sz = sdkp->capacity * (hard_sector/256); > > > > But those divides by 1250 and 1950 are still voodoo to me. > > > I think that just hides the real problem, and while that's useful to > stop the annoying numbers, the real problem is either (a) the value > calculated is wrong, (b) the size of sector_t is no longer large enough, > or (c) the type has been wrong all along and shouldn't be sector_t. > > If I understand what sector_t really is, (b) is my candidate. (b) is definitely the case with Dale's disk drive size. --- ~Randy - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
