aufs5.x-rcN-20200622.patch

diff -Naur null/Documentation/ABI/testing/debugfs-aufs linux-5.x-rcN/Documentation/ABI/testing/debugfs-aufs
--- /dev/null
+++ linux-5.x-rcN/Documentation/ABI/testing/debugfs-aufs	2020-07-09 11:04:45.296393810 +0200
@@ -0,0 +1,55 @@
+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>/xi0, xi1 ... xiN and xiN-N
+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.
diff -Naur null/Documentation/ABI/testing/sysfs-aufs linux-5.x-rcN/Documentation/ABI/testing/sysfs-aufs
--- /dev/null
+++ linux-5.x-rcN/Documentation/ABI/testing/sysfs-aufs	2020-07-09 11:04:45.296393810 +0200
@@ -0,0 +1,31 @@
+What:		/sys/fs/aufs/si_<id>/
+Date:		March 2009
+Contact:	J. R. Okajima <hooanon05g@gmail.com>
+Description:
+		Under /sys/fs/aufs, a directory named si_<id> is created
+		per aufs mount, where <id> is a unique id generated
+		internally.
+
+What:		/sys/fs/aufs/si_<id>/br0, br1 ... brN
+Date:		March 2009
+Contact:	J. R. Okajima <hooanon05g@gmail.com>
+Description:
+		It shows the abolute path of a member directory (which
+		is called branch) in aufs, and its permission.
+
+What:		/sys/fs/aufs/si_<id>/brid0, brid1 ... bridN
+Date:		July 2013
+Contact:	J. R. Okajima <hooanon05g@gmail.com>
+Description:
+		It shows the id of a member directory (which is called
+		branch) in aufs.
+
+What:		/sys/fs/aufs/si_<id>/xi_path
+Date:		March 2009
+Contact:	J. R. Okajima <hooanon05g@gmail.com>
+Description:
+		It shows the abolute path of XINO (External Inode Number
+		Bitmap, Translation Table and Generation Table) file
+		even if it is the default path.
+		When the aufs mount option 'noxino' is specified, it
+		will be empty. About XINO files, see the aufs manual.
diff -Naur null/Documentation/filesystems/aufs/design/01intro.txt linux-5.x-rcN/Documentation/filesystems/aufs/design/01intro.txt
--- /dev/null
+++ linux-5.x-rcN/Documentation/filesystems/aufs/design/01intro.txt	2020-07-09 11:04:45.296393810 +0200
@@ -0,0 +1,171 @@
+
+# Copyright (C) 2005-2020 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Introduction
+----------------------------------------
+
+aufs [ei ju: ef es] | /ey-yoo-ef-es/ | [a u f s]
+1. abbrev. for "advanced multi-layered unification filesystem".
+2. abbrev. for "another unionfs".
+3. abbrev. for "auf das" in German which means "on the" in English.
+   Ex. "Butter aufs Brot"(G) means "butter onto bread"(E).
+   But "Filesystem aufs Filesystem" is hard to understand.
+4. abbrev. for "African Urban Fashion Show".
+
+AUFS is a filesystem with features:
+- multi layered stackable unification filesystem, the member directory
+  is called as a branch.
+- branch permission and attribute, 'readonly', 'real-readonly',
+  'readwrite', 'whiteout-able', 'link-able whiteout', etc. and their
+  combination.
+- internal "file copy-on-write".
+- logical deletion, whiteout.
+- dynamic branch manipulation, adding, deleting and changing permission.
+- allow bypassing aufs, user's direct branch access.
+- external inode number translation table and bitmap which maintains the
+  persistent aufs inode number.
+- seekable directory, including NFS readdir.
+- file mapping, mmap and sharing pages.
+- pseudo-link, hardlink over branches.
+- loopback mounted filesystem as a branch.
+- several policies to select one among multiple writable branches.
+- revert a single systemcall when an error occurs in aufs.
+- and more...
+
+
+Multi Layered Stackable Unification Filesystem
+----------------------------------------------------------------------
+Most people already knows what it is.
+It is a filesystem which unifies several directories and provides a
+merged single directory. When users access a file, the access will be
+passed/re-directed/converted (sorry, I am not sure which English word is
+correct) to the real file on the member filesystem. The member
+filesystem is called 'lower filesystem' or 'branch' and has a mode
+'readonly' and 'readwrite.' And the deletion for a file on the lower
+readonly branch is handled by creating 'whiteout' on the upper writable
+branch.
+
+On LKML, there have been discussions about UnionMount (Jan Blunck,
+Bharata B Rao and Valerie Aurora) and Unionfs (Erez Zadok). They took
+different approaches to implement the merged-view.
+The former tries putting it into VFS, and the latter implements as a
+separate filesystem.
+(If I misunderstand about these implementations, please let me know and
+I shall correct it. Because it is a long time ago when I read their
+source files last time).
+
+UnionMount's approach will be able to small, but may be hard to share
+branches between several UnionMount since the whiteout in it is
+implemented in the inode on branch filesystem and always
+shared. According to Bharata's post, readdir does not seems to be
+finished yet.
+There are several missing features known in this implementations such as
+- for users, the inode number may change silently. eg. copy-up.
+- link(2) may break by copy-up.
+- read(2) may get an obsoleted filedata (fstat(2) too).
+- fcntl(F_SETLK) may be broken by copy-up.
+- unnecessary copy-up may happen, for example mmap(MAP_PRIVATE) after
+  open(O_RDWR).
+
+In linux-3.18, "overlay" filesystem (formerly known as "overlayfs") was
+merged into mainline. This is another implementation of UnionMount as a
+separated filesystem. All the limitations and known problems which
+UnionMount are equally inherited to "overlay" filesystem.
+
+Unionfs has a longer history. When I started implementing a stackable
+filesystem (Aug 2005), it already existed. It has virtual super_block,
+inode, dentry and file objects and they have an array pointing lower
+same kind objects. After contributing many patches for Unionfs, I
+re-started my project AUFS (Jun 2006).
+
+In AUFS, the structure of filesystem resembles to Unionfs, but I
+implemented my own ideas, approaches and enhancements and it became
+totally different one.
+
+Comparing DM snapshot and fs based implementation
+- the number of bytes to be copied between devices is much smaller.
+- the type of filesystem must be one and only.
+- the fs must be writable, no readonly fs, even for the lower original
+  device. so the compression fs will not be usable. but if we use