Pages isolated for migration are accounted with the vmstat counters
NR_ISOLATE_[ANON|FILE].  Callers of migrate_pages() are expected to
increment these counters when pages are isolated from the LRU.  Once the
pages have been migrated, they are put back on the LRU or freed and the
isolated count is decremented.

Memory failure is not properly accounting for pages it isolates causing
the NR_ISOLATED counters to be negative.  On SMP builds, this goes
unnoticed as negative counters are treated as 0 due to expected per-cpu
drift.  On UP builds, the counter is treated by too_many_isolated() as a
large value causing processes to enter D state during page reclaim or
compaction.  This patch accounts for pages isolated by memory failure
correctly.

[mel@csn.ul.ie: rewrote changelog]
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>