Merge branch 'akpm' (Andrew's patch-bomb)

* emailed from Andrew Morton <akpm@linux-foundation.org>: (21 patches)
  mm/memblock: fix overlapping allocation when doubling reserved array
  c/r: prctl: Move PR_GET_TID_ADDRESS to a proper place
  pidns: find_new_reaper() can no longer switch to init_pid_ns.child_reaper
  pidns: guarantee that the pidns init will be the last pidns process reaped
  fault-inject: avoid call to random32() if fault injection is disabled
  Viresh has moved
  get_maintainer: Fix --help warning
  mm/memory.c: fix kernel-doc warnings
  mm: fix kernel-doc warnings
  mm: correctly synchronize rss-counters at exit/exec
  mm, thp: print useful information when mmap_sem is unlocked in zap_pmd_range
  h8300: use the declarations provided by <asm/sections.h>
  h8300: fix use of extinct _sbss and _ebss
  xtensa: use the declarations provided by <asm/sections.h>
  xtensa: use "test -e" instead of bashism "test -a"
  xtensa: replace xtensa-specific _f{data,text} by _s{data,text}
  memcg: fix use_hierarchy css_is_ancestor oops regression
  mm, oom: fix and cleanup oom score calculations
  nilfs2: ensure proper cache clearing for gc-inodes
  thp: avoid atomic64_read in pmd_read_atomic for 32bit PAE
  ...

1 files changed, 10 insertions, 0 deletions

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 6f2b45a9b6b..ff4947b7a97 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -484,6 +484,16 @@ static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd)
 	/*
 	 * The barrier will stabilize the pmdval in a register or on
 	 * the stack so that it will stop changing under the code.
+	 *
+	 * When CONFIG_TRANSPARENT_HUGEPAGE=y on x86 32bit PAE,
+	 * pmd_read_atomic is allowed to return a not atomic pmdval
+	 * (for example pointing to an hugepage that has never been
+	 * mapped in the pmd). The below checks will only care about
+	 * the low part of the pmd with 32bit PAE x86 anyway, with the
+	 * exception of pmd_none(). So the important thing is that if
+	 * the low part of the pmd is found null, the high part will
+	 * be also null or the pmd_none() check below would be
+	 * confused.
 	 */
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	barrier();