ARM: fix some printk formats & Blacklist GCC 4.8.0 to GCC 4.8.2

We fix some printk formats for ptrdiff_t quantities which cause GCC
4.9 to complain, and we also blacklist known buggy GCC 4.8.x compilers
as their miscompilation is serious enough to cause filesystem
corruption, even through many distros have fixed their versions"

* 'fixes' of git://ftp.arm.linux.org.uk/~rmk/linux-arm:
ARM: fix some printk formats
ARM: Blacklist GCC 4.8.0 to GCC 4.8.2 - PR58854
ARM: 8180/1: mm: implement no-highmem fast path in kmap_atomic_pfn()

Since CONFIG_HIGHMEM got enabled on ARMv5 Kirkwood, we have noticed a
very significant drop in networking performance. The test were
conducted on an OpenBlocks A7 board. Without this patch, the outgoing
performance measured with iperf are:

- highmem OFF, TSO OFF   544 Mbit/s
- highmem OFF, TSO ON	  942 Mbit/s
- highmem ON,  TSO OFF   306 Mbit/s
- highmem ON,  TSO ON    246 Mbit/s

On this Kirkwood platform, the L2 cache is a Feroceon cache, and with
this cache, all the range operations have to be done on virtual
addresses and not physical addresses. Therefore, whenever
CONFIG_HIGHMEM is enabled, the cache maintenance operations call
kmap_atomic_pfn() and kunmap_atomic().

However, kmap_atomic_pfn() does not implement the same fast path for
non-highmem pages as the one implemented in kmap_atomic(), and this is
one of the reason for the performance drop. While this patch does not
fully restore the performances, it clearly improves them a lot:

      	      	        without patch  with patch

- highmem ON, TSO OFF   306 Mbit/s     387 Mbit/s
- highmem ON, TSO ON    246 Mbit/s     434 Mbit/s

We're still far from the !CONFIG_HIGHMEM performances, but it does
improve a bit the situation.

Thanks a lot to Ezequiel Garcia and Gregory Clement for all the
testing work around this topic.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
switch do_fsync() to fget_light()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>