[PATCH v5 0/3] mm: fixes of tlb_flush_pending

[Nadav Amit <namit@vmware.com>]

These three patches address tlb_flush_pending issues. The first one address
a race when accessing tlb_flush_pending and is the important one.

The next two patch addresses Andrew Morton question regarding the barriers.
This patch is not really related to the first one: the atomic operations
atomic_read() and atomic_inc() do not act as a memory barrier, and
replacing existing barriers with smp_mb__after_atomic() did not seem
beneficial. Yet, while reviewing the memory barriers around the use of
tlb_flush_pending, few issues were identified.

v4 -> v5:
 - Fixing embarrassing build mistake (0day)

v3 -> v4:
 - Change function names to indicate they inc/dec and not set/clear
   (Sergey)
 - Avoid additional barriers, and instead revert the patch that accessed
   mm_tlb_flush_pending without a lock (Mel)

v2 -> v3:
 - Do not init tlb_flush_pending if it is not defined without (Sergey)
 - Internalize memory barriers to mm_tlb_flush_pending (Minchan) 

v1 -> v2:
 - Explain the implications of the implications of the race (Andrew)
 - Mark the patch that address the race as stable (Andrew)
 - Add another patch to clean the use of barriers (Andrew)

Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>


Nadav Amit (3):
  mm: migrate: prevent racy access to tlb_flush_pending
  mm: migrate: fix barriers around tlb_flush_pending
  Revert "mm: numa: defer TLB flush for THP migration as long as
    possible"

 include/linux/mm_types.h | 45 ++++++++++++++++++++++++++++++++-------------
 kernel/fork.c            |  2 +-
 mm/debug.c               |  2 +-
 mm/huge_memory.c         |  7 +++++++
 mm/migrate.c             |  6 ------
 mm/mprotect.c            |  4 ++--
 6 files changed, 43 insertions(+), 23 deletions(-)

-- 
2.11.0

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