fs: ext4: fix symlink read function ...

From U-Boot commit:

| commit 37f2388
| Author: Ronald Zachariah <rozachar@cisco.com>
| Date:   Thu Apr 28 07:08:34 2016 +0200
|
|     fs: ext4: fix symlink read function
|
|     The function ext4fs_read_symlink was unable to handle a symlink
|     which had target name of exactly 60 characters.
|
|     Signed-off-by: Ronald Zachariah <rozachar@cisco.com>
|     Signed-off-by: Stefan Roese <sr@denx.de>
|     Reviewed-by: Stephen Warren <swarren@nvidia.com>
|     Cc: Tom Rini <trini@konsulko.com>

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

fs: ext4: make locally used ext4fs_get_indir_block() static ...

The patch fixes this compiler's warning:

      CC      fs/ext4/ext4_common.o
    fs/ext4/ext4_common.c:130:5: warning: no previous prototype for
    'ext4fs_get_indir_block' [-Wmissing-prototypes]
     int ext4fs_get_indir_block(struct ext2fs_node *node, struct
    ext4fs_indir_block *indir, int blkno)
         ^

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>

drop <stddef.h> includes ...

The compilers stddef.h should not be included. We declare all types
ourselves.

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

fs: rename inode member of struct filep to priv ...

Because that's what it is. 'inode' will become confusing
once we support real inodes.

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

fs: ext4: le32_to_cpu() used on a 16-bit field ...

From U-Boot commit:

| commit 8b415f7
| Author: Rommel Custodio <sessyargc+uboot@gmail.com>
| Date:   Sun Jul 21 10:53:25 2013 +0200
|
|     ext4fs: le32_to_cpu() used on a 16-bit field
|
|     Fix reading ext4_extent_header struture on BE machines.  Some 16 bit
|     fields where converted to 32 bit fields, due to the byte swap on BE
|     machines the containing value was corrupted. Therefore reading ext4
|     filesystems on BE machines where broken before.
|
|     Signed-off-by: Rommel Custodio <sessyargc+uboot@gmail.com>
|     [sent via git-send-email; rework commit message]
|     Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
|     Reviewed-by: Simon Glass <sjg@chromium.org>
|     Tested-by: Simon Glass <sjg@chromium.org>
|     Tested-by: Lukasz Majewski <l.majewski@samsung.com>

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

fs: ext4: use EXT2_BLOCK_SIZE instead of fs->blksz ...

From U-Boot commit:

| commit 4701732
| Author: Ionut Nicu <ioan.nicu.ext@nsn.com>
| Date:   Mon Jan 13 11:59:24 2014 +0100
|
|     ext4fs: use EXT2_BLOCK_SIZE instead of fs->blksz
|
|     Using fs->blksz in ext4fs_get_extent_block() is not
|     correct since fs->blksz is not initialized on the
|     read path. Use EXT2_BLOCK_SIZE() instead which will
|     produce the desired output.
|
|     Signed-off-by: Ionut Nicu <ioan.nicu.ext@nsn.com>
|     Signed-off-by: Mathias Rulf <mathias.rulf@nsn.com>

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

fs: ext4: fix "invalid extent block" error ...

From U-Boot commit:

| commit b5bbac1
| Author: Ionut Nicu <ioan.nicu.ext@nsn.com>
| Date:   Mon Jan 13 12:00:08 2014 +0100
|
|     ext4fs: fix "invalid extent block" error
|
|     For files where we actually have extent indexes following
|     an extent header (ext_block->eh_depth != 0), the do/while
|     loop from ext4fs_get_extent_block() does not select the
|     proper extent index structure.
|
|     For example, if we have:
|
|     ext_block->eh_depth = 1
|     ext_block->eh_entries = 1
|     fileblock = 0
|     index[0].ei_block = 0
|
|     the do/while loop will exit with i set to 0 and the
|     ext4fs_get_extent_block() function will return 0, even if
|     there was a valid extent index structure following the
|     header.
|
|     Signed-off-by: Ionut Nicu <ioan.nicu.ext@nsn.com>
|     Signed-off-by: Mathias Rulf <mathias.rulf@nsn.com>

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

fs: cleanup backingstore handling ...

All filesystem drivers which need a backingstore device do the same
ignoring of '/dev/' in the backingstore followed by a cdev_open. Add a
helper function for it and let the core handle the cdev. As a side
effect this makes sure that fsdev->cdev is also set when a device is
mounted without the leading '/dev/' which was previously ignored
by the mount code.

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

ext4: switch debug and printf to dev_xxx ...

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.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>