[LTP] [PATCH] mbind_range() vma merge

[<ca...@re...>]

This is a reproducer from mainline commit
9d8cebd4bcd7c3878462fdfda34bbcdeb4df7ef4:

"Strangely, current mbind() doesn't merge vma with neighbor vma although
it's possible.  Unfortunately, many vma can reduce performance..."

Signed-off-by: CAI Qian <ca...@re...>
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