Added some documentation in exofs.txt, as well as a BUGS file.

For further reading, operation instructions, example scripts
and up to date infomation and code please see:
http://open-osd.orgSigned-off-by: NBoaz Harrosh <bharrosh@panasas.com>

implement export_operations and set in superblock.
It is now posible to export exofs via nfs
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>

This patch ties all operation vectors into a file system superblock
and registers the exofs file_system_type at module's load time.

* The file system control block (AKA on-disk superblock) resides in
  an object with a special ID (defined in common.h).
  Information included in the file system control block is used to
  fill the in-memory superblock structure at mount time. This object
  is created before the file system is used by mkexofs.c It contains
  information such as:
	- The file system's magic number
	- The next inode number to be allocated
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>

implementation of directory and inode operations.

* A directory is treated as a file, and essentially contains a list
  of <file name, inode #> pairs for files that are found in that
  directory. The object IDs correspond to the files' inode numbers
  and are allocated using a 64bit incrementing global counter.
* Each file's control block (AKA on-disk inode) is stored in its
  object's attributes. This applies to both regular files and other
  types (directories, device files, symlinks, etc.).
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>

OK Now we start to read and write from osd-objects. We try to
collect at most contiguous pages as possible in a single write/read.
The first page index is the object's offset.

TODO:
   In 64-bit a single bio can carry at most 128 pages.
   Add support of chaining multiple bios
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>

Generic implementation of symlink ops.
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>

implementation of the file_operations and inode_operations for
regular data files.

Most file_operations are generic vfs implementations except:
- exofs_truncate will truncate the OSD object as well
- Generic file_fsync is not good for none_bd devices so open code it
- The default for .flush in Linux is todo nothing so call exofs_fsync
  on the file.
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>

This patch includes osd infrastructure that will be used later by
the file system.

Also the declarations of constants, on disk structures,
and prototypes.

And the Kbuild+Kconfig files needed to build the exofs module.
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>