Patch series "add crc64 calculation as kernel library", v5.

This patchset adds basic implementation of crc64 calculation as a Linux
kernel library.  Since bcache already does crc64 by itself, this patchset
also modifies bcache code to use the new crc64 library routine.

Currently bcache is the only user of crc64 calculation, another potential
user is bcachefs which is on the way to be in mainline kernel.  Therefore
it makes sense to make crc64 calculation to be a public library.

bcache uses crc64 as storage checksum, if a change of crc lib routines
results an inconsistent result, the unmatched checksum may make bcache
'think' the on-disk is corrupted, such a change should be avoided or
detected as early as possible.  Therefore a patch is being prepared which
adds a crc test framework, to check consistency of different calculations.

This patch (of 2):

Add the re-write crc64 calculation routines for Linux kernel.  The CRC64
polynomical arithmetic follows ECMA-182 specification, inspired by CRC
paper of Dr.  Ross N.  Williams (see
http://www.ross.net/crc/download/crc_v3.txt) and other public domain
implementations.

All the changes work in this way,
- When Linux kernel is built, host program lib/gen_crc64table.c will be
  compiled to lib/gen_crc64table and executed.
- The output of gen_crc64table execution is an array called as lookup
  table (a.k.a POLY 0x42f0e1eba9ea369) which contain 256 64-bit long
  numbers, this table is dumped into header file lib/crc64table.h.
- Then the header file is included by lib/crc64.c for normal 64bit crc
  calculation.
- Function declaration of the crc64 calculation routines is placed in
  include/linux/crc64.h

Currently bcache is the only user of crc64_be(), another potential user is
bcachefs which is on the way to be in mainline kernel.  Therefore it makes
sense to move crc64 calculation into lib/crc64.c as public code.

[colyli@suse.de: fix review comments from v4]
  Link: http://lkml.kernel.org/r/20180726053352.2781-2-colyli@suse.de
Link: http://lkml.kernel.org/r/20180718165545.1622-2-colyli@suse.deSigned-off-by: Coly Li <colyli@suse.de>
Co-developed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Michael Lyle <mlyle@lyle.org>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Noah Massey <noah.massey@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>