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XINO and XIB files are to maintain the inode numbers in aufs
(cf. struct.txt and aufs manual in aufs-util.git).

XINO file contains just a sequence of the inode numbers, and their
offset in the file is real_inum x sizeof(inum).  So the size is limited
by s_maxbytes of the filesystem where XINO file is located.  In order to
support the larger inum, aufs stores XINO files as an internal array.

Sometimes the size of XINO file can be a problem, ie. too big,
particularly when XINO files are located on tmpfs. In this case, another
separate patch tmpfs-ino.patch in aufs4-standalone.git is recommended
(as well as vfs-ino.patch). The patch makes tmpfs to maintain inode
number within itself and suppress its discontiguous distribution.

See also the document in next commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

Aufs uses the workqueue both synchronously and asynchronously.
For sync-use-case, aufs uses its own specific wkq since doesn't want to
be disturbed by other tasks on the system. For async-use-case, aufs uses
the system global workqueue.
Aufs has to prevent itself to being unmounted during the async-task is
queued.

See also the document in this commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

The branch object is managed by the sbinfo object as an element of its
internal array. The iinfo and dinfo objects contain the branch id, and
it will be used to implement the correct order in branch management
(add/del).

See also the documents in this commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

The generation of iinfo and dinfo inherit sbinfo's.
Also iinfo generation tracks the branch inode's generation to test the
matching after the branch management.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

The structure is very similar to aufs inode info (in previous commit).
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

Print various info about aufs inode. This feature is enabled when
CONFIG_AUFS_DEBUG and the module parameter 'debug' are set.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

This parameter is available only when CONFIG_AUFS_DEBUG is enabled, and
its default value is 0. Setting 1 will enable the various verifications
and debug outputs.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

This is a very old debugging routine for rw_semaphore I was using
privately and less meaningful to other people. It was (probably) before
LOCKDEP feature was introduced, but now it is based upon LOCKDEP. This
is compiled when CONFIG_AUFS_DEBUG is enabled.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

See the documents in this commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

Very basic, simple and stupid wrappers for kmalloc family.
It tries kfree_ruc() as possible, with hoping a better performance.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>