Actual usage of files in ubifs

[Richard Weinberger]

Am Montag, 11. September 2017, 17:44:09 CEST schrieb Artem Bityutskiy:
> > Good point. I was solely thinking along the lines of how much space
> > the
> > actual file occupied, not considering metadata. That would be a good
> > starting point. I'm guessing that for moderate file sizes the
> > metadata
> > would be relatively small compared to the file itself?
> 
> I would think a "slow" version of this would not be that hard to
> implement - walk the index and sum up node sizes. Subtract header sizes
> if you do not want metadata.
> 
> I am not sure what would be the API? Do other FSes implement something
> like this?

I think a "show MTD usage by inode" should be implementable via debugfs.
Maybe, after a discussion on linux-fsdevel a per-file ioctl().

But first I'd like to know more about the use-case and where to draw the 
border.
e.g. If a file as xattrs, do you also account them? UBIFS modules xattrs
via inodes. So, they have a rather huge space overhead.

Thanks,
//richard

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