On 30/08/08 18:45, Matthew Wilcox wrote: > On Sat, Aug 30, 2008 at 12:24:50PM -0500, James Bottomley wrote: >> No, this is wrong. By mandated standards the manufacturers are allowed >> to calculate MB by dividing by 10^6. This is a fiddle to allow them to >> make their drives look slightly bigger. However, we want the printed >> information to match that written on the drive, so in this printk, we >> use the manufacturer standard for calculation (and then do everything >> else in bytes so we don't have to bother with it ever again). It's unlikely to match what's on the drive, "1000204886016" isn't 1TB by any standard. > I was looking at this code recently because it looks really bizarre when > you create a half-petabyte filesystem: > > $ sudo insmod drivers/ata/ata_ram.ko capacity=1099511627776 preallocate=0 > > [12095.028093] ata7.00: 1099511627776 sectors, multi 0: LBA48 NCQ (depth 31/32) > [12095.028093] ata7.00: configured for UDMA/133 > [12095.041915] scsi 7:0:0:0: Direct-Access ATA Linux RAM Drive 0.01 PQ: 0 ANSI: 5 > [12095.041915] sd 7:0:0:0: [sdc] Very big device. Trying to use READ CAPACITY(16). > [12095.041915] sd 7:0:0:0: [sdc] 1099511627776 512-byte hardware sectors (562949953 MB) > [12095.041915] sd 7:0:0:0: [sdc] Write Protect is off > [12095.041915] sd 7:0:0:0: [sdc] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA This looks useful for testing this... do you have an updated version? > 1. Avoiding 64-bit divisions is _so_ last decade. We have > linux/math64.h, we should use it. > > 2. We should report in GB or TB when appropriate. The exact definition > of 'appropriate' is going to vary from person to person. Might I > suggest that we should report between two and four significant digits. > eg 9543 MB is ok, 10543 MB should be 10 GB. I've gone with five digits, it switches to GB at ~98GB, and to TB at ~98TB etc. > 3. I hate myself for saying this ... but maybe we should be using the > horrific MiB/GiB/TiB instead of MB/GB/TB. Somehow this stuff got into net-tools (ifconfig) too, so I have a patch to remove it from my systems. > 4. I've been far too busy to write said patch. Simon, would you mind > doing the honours? Sure, patch will follow this email... it can only go as far as 8192EB and then there's not enough space to store more than 2^64 512-byte sectors. (And if you only modify drivers/scsi/sd.c, the kernel make system won't recompile sd.o!) -- Simon Arlott -- To unsubscribe from this list: 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
