What:		/debug/aufs/si_<id>/
Date:		March 2009
Contact:	J. R. Okajima <hooanon05g@gmail.com>
Description:
		Under /debug/aufs, a directory named si_<id> is created
		per aufs mount, where <id> is a unique id generated
		internally.

What:		/debug/aufs/si_<id>/plink
Date:		Apr 2013
Contact:	J. R. Okajima <hooanon05g@gmail.com>
Description:
		It has three lines and shows the information about the
		pseudo-link. The first line is a single number
		representing a number of buckets. The second line is a
		number of pseudo-links per buckets (separated by a
		blank). The last line is a single number representing a
		total number of psedo-links.
		When the aufs mount option 'noplink' is specified, it
		will show "1\n0\n0\n".

What:		/debug/aufs/si_<id>/xib
Date:		March 2009
Contact:	J. R. Okajima <hooanon05g@gmail.com>
Description:
		It shows the consumed blocks by xib (External Inode Number
		Bitmap), its block size and file size.
		When the aufs mount option 'noxino' is specified, it
		will be empty. About XINO files, see the aufs manual.

What:		/debug/aufs/si_<id>/xi<branch-index>
Date:		March 2009
Contact:	J. R. Okajima <hooanon05g@gmail.com>
Description:
		It shows the consumed blocks by xino (External Inode Number
		Translation Table), its link count, block size and file
		size.
		Due to the file size limit, there may exist multiple
		xino files per branch.  In this case, "-N" is added to
		the filename and it corresponds to the index of the
		internal xino array.  "-0" is omitted.
		When the aufs mount option 'noxino' is specified, Those
		entries won't exist.  About XINO files, see the aufs
		manual.

What:		/debug/aufs/si_<id>/xigen
Date:		March 2009
Contact:	J. R. Okajima <hooanon05g@gmail.com>
Description:
		It shows the consumed blocks by xigen (External Inode
		Generation Table), its block size and file size.
		If CONFIG_AUFS_EXPORT is disabled, this entry will not
		be created.
		When the aufs mount option 'noxino' is specified, it
		will be empty. About XINO files, see the aufs manual.