Sometimes gcc mysteriously doesn't inline
very small functions we expect to be inlined. See

    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122

With this .config:
http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os,
the following functions get deinlined many times.
Examples of disassembly:

<SetPageUptodate> (43 copies, 141 calls):
       55                      push   %rbp
       48 89 e5                mov    %rsp,%rbp
       f0 80 0f 08             lock orb $0x8,(%rdi)
       5d                      pop    %rbp
       c3                      retq

<PagePrivate> (10 copies, 134 calls):
       48 8b 07                mov    (%rdi),%rax
       55                      push   %rbp
       48 89 e5                mov    %rsp,%rbp
       48 c1 e8 0b             shr    $0xb,%rax
       83 e0 01                and    $0x1,%eax
       5d                      pop    %rbp
       c3                      retq

This patch fixes this via s/inline/__always_inline/.

Code size decrease after the patch is ~7k:

    text     data      bss       dec     hex filename
92125002 20826048 36417536 149368586 8e72f0a vmlinux
92118087 20826112 36417536 149361735 8e71447 vmlinux7_pageops_after
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>