fs: ext4: Switch to dentry cache implementation ...

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ext4: Update ext2/3/4 superblock, group descriptor and inode structures ...

This is an adoption of the U-Boot commit

| commit 3ee2f97
| Author: Stefan Brüns <stefan.bruens@rwth-aachen.de>
| Date:   Sat Sep 17 02:10:06 2016 +0200
|
|     ext4: Update ext2/3/4 superblock, group descriptor and inode structures
|
|     Most importantly, the superblock provides the used group descriptor size,
|     which is required for the EXT4_FEATURE_INCOMPAT_64BIT.
|
|     Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ext4: drop unused and misdefined INODE_SIZE_FILESYSTEM macro ...

Nota bene sblock.inode_size actually has __le16 type.

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ext4: use kernel names for byte swaps ...

This is an adoption of the U-Boot commit

| commit 7f101be
| Author: Michael Walle <michael@walle.cc>
| Date:   Mon Aug 29 10:46:44 2016 +0200
|
|     ext4: use kernel names for byte swaps
|
|     Instead of __{be,le}{16,32}_to_cpu use {be,le}{16,32}_to_cpu.
|
|     Signed-off-by: Michael Walle <michael@walle.cc>

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ext4: change structure fields to __le/__be types ...

This is an adoption of the U-Boot commit

| commit 2a0b7a9
| Author: Michael Walle <michael@walle.cc>
| Date:   Mon Aug 29 10:46:43 2016 +0200
|
|     ext4: change structure fields to __le/__be types
|
|     Change all the types of ext2/4 fields to little endian types and all the
|     JBD fields to big endian types. Now we can use sparse (make C=1) to check
|     for statements where we need byteswaps.
|
|     Signed-off-by: Michael Walle <michael@walle.cc>

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

fs: import magic.h from Linux kernel ...

include/linux/magic.h provides MAGIC numbers for various
file systems.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

fs: implement initial ext4 support from U-Boot ...

The ext4 implementation has been taken from U-Boot with some
changes:

- No global variables to allow for multiple filesystems to
  be mounted and multiple files to be open.
- remove fs internal link following and use the barebox link
  implementation.
- remove write support. This is incomplete in U-Boot, so I decided
  to skip this for now.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>