Makefile: remove KREL

The KREL macro defined in the Makefile isn't used, although the "make -s
kernelrelease" command that is run as part of its definition causes a
non-fatal build error when the kernel is built outside its source
directory, for example, in distros such as Debian and Ubuntu:

/usr/src/linux-headers-4.9.0-3-common/scripts/Makefile.build:44: /usr/src/linux-headers-4.9.0-3-common/scripts/basic/Makefile: No such file or directory
make[4]: *** No rule to make target '/usr/src/linux-headers-4.9.0-3-common/scripts/basic/Makefile'.  Stop.
make[3]: *** [scripts_basic] Error 2

The Makefile carries on to build the module after this error.  Just
remove the KREL macro to avoid it in the first place.

exfat: Stop using CURRENT_TIME_SEC

 * This is going away in 4.12 and is not y2038 safe.
 * Use current_time(inode) and ktime_get_real_ts where appropriate.

dkms: Support building for non-current kernel.

exfat_super: Update for kernel 4.11 compatibility

In Linux kernel 4.11, the prototype of getattr function changed.

Use the new prototype and change inode acquring code, when kernel
version > 4.11.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>

fix compilation error for kernel 2.6.36.

exfat_super: Update for kernel 4.10 compatibility

If no special .readlink is required, it should be left uninitialised.

Add support for NFS

Fix leak for symbolic link in exfat_lookup

While exfat_lookup() for symbolic file, we Should not alloc memory
to EXFAT_I(inode)->target since the corredspoding exfat inode info
is still is in memory and EXFAT_I(inode)->target has not released
yet. If we do so, memory leak would happen. Therefore we only alloc
it if not null.

Reviewed-by: Ethan Wu <ethanwu@synology.com>
Signed-off-by: Chung-Chiang Cheng <cccheng@synology.com>

Support exfat capacity more than 2TB

- Change the size of num_sectors in memory to 64 bits as it is in on-disk
  structure.
- Use type 'sector_t' for all sector variables.
- Fix overflow issue of macro START_SECTOR(x)

Reviewed-by: Peter Huang <peterh@synology.com>
Signed-off-by: Chung-Chiang Cheng <cccheng@synology.com>

This fix was added to all FS drivers in 3.6.0 -rc7 and was missing here.
https://github.com/torvalds/linux/commit/8c0a85377048b64c880e76ec7368904fe46d0b94

build: Common exFAT KM build target for reuse by devices

exfat_super: Update for kernel 4.9 compatibility

The following changes have been made in kernel 4.9 that necessitate
changes

* inode_change_ok has been replaced by setattr_prepare, which takes a
dentry as its argument for security reasons

* rename's interface has changed to require an additional argument for
flags. Since we do not support rename flags, passing flags will always
return -EINVAL

Signed-off-by: Evan Anderson <evan@eaanderson.com>

Devices can still use their own build targets, or can simply
include the exfat-km.mk herein into their BoardConfig
(or call inherit-product in other device MK).

Compatible with the inline kernel building in CM13/4, and similar.

Change-Id: Ib50654d2925ac26233e1c984e079990b70383dae

Update README.md to include DKMS instructions

New file: dkms.conf

exfat: finding dentry faster

exfat_super.c: Support kernel 4.8

core: Fix -Wmisleading-indentation in ffsMountVol()

Changes introduced by commits 8387ff2577e and 6fa67e707 in the kernel
prompted this change.

Signed-off-by: Evan Anderson <evananderson@thelinuxman.us>

We don't need to read all the dentry and compare them
one by one. Skip reading the useless dentries to fast
the dentry finding speed.

Also add back the name_hash to compare it more faster.

Signed-off-by: Lianwei Wang <lianwei.wang@gmail.com>

Add support for Linux 4.7

superblock: All 3.4 kernels need end_writeback()

Change-Id: I5b0e702cf00c5f58e5db5b32bd5f8438f4203273

Update symlink support for Linux 4.5