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Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>
(cherry picked from commit 56b4b776c84f364384971c4cdfd66b4a2f0696d4)

Print the current data status for debugging.
The trigger key is a module parameter and you can freely change. The
default is 'a' of course.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

Simple checks when the module is loaded.
This feature is compiled when CONFIG_AUFS_DEBUG is enabled.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

This commit is just to prepare for the succeeding commit, and split to
suppress the size of a single commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

The structure is very similar to iinfo and dinfo (in previous commits).
This commit is for non-dir files. For a directory, see later commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

As a result of branch management, the virtual inode may point a
different real inode from it used to. And aufs has to maintain its
address_space_operations, since its definition may affect the
behaviour.
I know some people (including grsec-patch) doesn't like a non-const
address_space_operations, but in order to keep the consistency of the
behaviour, the correct address_space_operations is important.

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

To create/delete/rename files including copy-up, aufs acquires several
locks on the branch fs internally. These lock/unlock operations are
consolidated into struct au_pin in this commit.
au_pin handles
- LOCKDEP class
- re-validate/verify
- suspend/resume HNOTIFY

See also lookup.txt in later commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

As mentioned earlier, sometimes the size of XINO file is a problem.
Aufs has a feature to truncate it asynchronously using workqueue. But it
may not be so effective in some cases, and you may want to stop
discontiguous distribution of the inode numbers on branch fs.
See also the log in another commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

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>

Print various info about aufs branch and superblock. This feature is
enabled when CONFIG_AUFS_DEBUG and the module parameter 'debug' are set.
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 inode and dentry infos (in previous
commits), but the internal array is for 'struct au_branch' instead of
'superblock.' Additionally the lifetime of 'struct au_sbinfo' is managed
by kobject since it will be connected to sysfs by later commit.
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>

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>