Pull ACCESS_ONCE() rule tightening from Christian Borntraeger:
 "Tighten rules for ACCESS_ONCE

  This series tightens the rules for ACCESS_ONCE to only work on scalar
  types.  It also contains the necessary fixups as indicated by build
  bots of linux-next.  Now everything is in place to prevent new
  non-scalar users of ACCESS_ONCE and we can continue to convert code to
  READ_ONCE/WRITE_ONCE"

* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux:
  kernel: Fix sparse warning for ACCESS_ONCE
  next: sh: Fix compile error
  kernel: tighten rules for ACCESS ONCE
  mm/gup: Replace ACCESS_ONCE with READ_ONCE
  x86/spinlock: Leftover conversion ACCESS_ONCE->READ_ONCE
  x86/xen/p2m: Replace ACCESS_ONCE with READ_ONCE
  ppc/hugetlbfs: Replace ACCESS_ONCE with READ_ONCE
  ppc/kvm: Replace ACCESS_ONCE with READ_ONCE

This allows the get_user_pages_fast slow path to release the mmap_sem
before blocking.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 927609d622a3 ("kernel: tighten rules for ACCESS ONCE") results in a
compile failure for sh builds with CONFIG_X2TLB enabled.

arch/sh/mm/gup.c: In function 'gup_get_pte':
arch/sh/mm/gup.c:20:2: error: invalid initializer
make[1]: *** [arch/sh/mm/gup.o] Error 1

Replace ACCESS_ONCE with READ_ONCE to fix the problem.

Fixes: 927609d622a3 ("kernel: tighten rules for ACCESS ONCE")
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

This patch avoids fuse hangs on sh4 by flushing the cache on
get_user_pages_fast().  This is not necessary a good thing to do, but
get_user_pages() does this, so get_user_pages_fast() should too.

Please note the patch for mips arch that addresses the similar problem:
  https://kernel.googlesource.com/pub/scm/linux/kernel/git/ralf/linux/+/linux-3.4.50%5E!/#F0

They basically simply disable get_user_pages_fast() at all, using a
fall-back to get_user_pages().  But my fix is different, it adds an
explicit cache flushes.

Signed-off-by: Stas Sergeev <stsp@users.sourceforge.net>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Kamal Dasu <kdasu.kdev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Implement get_user_pages_fast without locking in the fastpath on sh.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>