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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>

For details, see previous 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 generation of aufs objects will be updated by the branch
management (add/del branches, by later commit), and aufs will refresh
the objects based upon the generation.
In refreshing dinfos, aufs will find all ancestors of the given dentry
and store the pointers in dynamically allocated memory. I don't think it
beautiful, but I don't have any other idea.
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>

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>

A header file for both of kernelspace and userspace.

For the new file fs/aufs/Kconfig, the maximum number of branches is
customizable, and it determines the type (size) of 'aufs_bindex_t.' The
type is always 'signed.' If we made it 'unsigned,' then more branches
would be available. But generally I think 127 (default) is enough and it
won't be a big issue.

For those who wants more than 127 branches, other values are
available. But we should care the size of the internal pointer arrays,
and it is good for the performance to keep it in a page at most.
AUFS_BRANCH_MAX_511 is mainly for 64bit systems which limits the
internal array size less than 4k (511 x 8bytes < 4k). Similarly for
32bit systems, AUFS_BRANCH_MAX_1023 (1023 x 4 bytes < 4k).

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