On Thu, 12 Feb 2015 15:25:08 -0800 James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > On Thu, 2015-02-12 at 15:01 -0800, akpm@xxxxxxxxxxxxxxxxxxxx wrote: > > From: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> > > Subject: lib/string_helpers.c:string_get_size(): remove redundant prefixes > > > > While 3c9f3681d0b4 "[SCSI] lib: add generic helper to print sizes rounded > > to the correct SI range" says that Z and Y are included in preparation for > > 128 bit computers, they just waste .text currently. If and when we get > > u128, string_get_size needs updating anyway (and ISO needs to come up with > > four more prefixes). > > This is rubbish. It's nothing to do with 128 bits. This is to do with > disk sizes linux gets attached to. The current largest device clusters > are Petabytes ... I think we may have some exabyte ones somewhere in the > Academic community, so it's by no means inconcievable we'll have > Zettabyte ones within a few years. The SCSI standard, with 4k blocks > supports up to 2^76, which is well into Zettabytes. We obviously run > off the mmap possibilities a lot sooner, because of the byte offsets, > but that's fixable. Someone will probably start first by passing blocks > into that interface not bytes, so we'd like it not to be based on > assumptions that think 2^64 is the largest possible value. I don't get it. As the man says, this is presently dead code and string_get_size() will need to be changed to work for disks larger than 2^64 bytes. That change may be to take a u128 or it may be as you suggest: replace the `u64 size' with `u64 size, u64 units' which is effectively the same thing. > > Also there's no need to include and test for the NULL sentinel; once we > > reach "E" size is at most 18. [The test is also wrong; it should be > > units_str[units][i+1]; if we've reached NULL we're already doomed.] > > So fix the bug, don't set us up to run off the end of the array. And > please consult the community which keeps track of this rather than > trying to get it into Linux without review. That seems a bit harsh - you've been cc'ed on this every step of the way. -- 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
