Re: udf: Suspicious values in udf_statfs()

[Jan Kara <jack@suse.cz>]

On Thu 16-01-20 16:30:19, Pali Rohár wrote:
> On Monday 13 January 2020 13:08:51 Jan Kara wrote:
> > > Second one:
> > > 
> > > 	buf->f_files = (lvidiu != NULL ? (le32_to_cpu(lvidiu->numFiles) +
> > > 					  le32_to_cpu(lvidiu->numDirs)) : 0)
> > > 			+ buf->f_bfree;
> > > 
> > > What f_files entry should report? Because result of sum of free blocks
> > > and number of files+directories does not make sense for me.
> > 
> > This is related to the fact that we return 'f_bfree' as the number of 'free
> > file nodes' in 'f_ffree'. And tools generally display f_files-f_ffree as
> > number of used inodes. In other words we treat every free block also as a
> > free 'inode' and report it in total amount of 'inodes'. I know this is not
> > very obvious but IMHO it causes the least confusion to users reading df(1)
> > output.
> 
> So current code which returns sum of free blocks and number of
> files+directories is correct. Could be this information about statvfs
> f_files somewhere documented? Because this is not really obvious nor for
> userspace applications which use statvfs() nor for kernel filesystem
> drivers.

Well, I can certainly add a comment to udf_statfs(). Documenting in some
manpage might be worth it but I'm not 100% sure where - maybe directly in
the statfs(2) to the NOTES section? Also note that this behavior is not
unique to UDF - e.g. XFS also does the same.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR