On 01/21/2013 10:03 AM, Kevin Wolf wrote: > Am 21.01.2013 17:27, schrieb Eric Blake: >> On 01/21/2013 07:25 AM, Federico Simoncelli wrote: >>> This patch adds the support for reporting the highest offset in use by >>> an image. This is particularly useful after a conversion (or a rebase) >>> where the destination is a block device in order to find the actual >>> amount of space in use.
>>> + if (result.highest_offset > 0) { >>> + printf("Highest offset in use: %" PRId64 "\n", >>> result.highest_offset); >> >> This output message feels off by one. Either you need to subtract 1 >> from res->highest_offset to get the address of the last used byte, or >> you need to document it as the first unused byte, or instead of calling >> it 'highest offset', you should call it 'used bytes' (except that with >> sparse files, it's hard to argue that all earlier bytes were 'used'). > > Good point. I think the number is what we wanted, and what users are > interested in is probably "used bytes" rather than "first unused byte". > Maybe we can find a better word for "used" (it has the same problem in > all three contexts), but I can't think of one off the top of my head. "Allocation" alone isn't good (because of sparse files, not all earlier bytes are allocated). But maybe "Offset of unallocated tail: ..." works, to make it clear that there may be other unallocated portions earlier, but that all bytes at the listed offset and beyond are unallocated. For a file that is completely allocated, or even for a sparse file but with no unallocated tail, the value would be the same as the file capacity. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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