[COMMON] mm: gup: drain pagevec if FOLL_CMA is set

[COMMON] mm: gup: drain pagevec if FOLL_CMA is set

Some users of get_user_pages() give FOLL_CMA not to pin CMA pages.
However a CMA page may not be migrated even though FOLL_CMA is set
because it is not in LRU but in per-cpu pagevec.
The previous approach to solve this problem is the invocation of
migrate_prep_local() that drains the pagevec of the local CPU. It was
the only choice in if it is called in __need_migrate_cma_page(). It is
because __need_migrate_cma_page() is called under a spinlock of page
table is held. This approach unfortunately does not drain pagevecs of
other CPUs and makes CMA fail to allocate physically contiguous memory
at last.
We need a different approach to get over the problem: clearing pagevec
of all CPUs if FOLL_CMA is set unconditionally. It degrades the
performance of get_user_pages() with FOLL_CMA if no CMA page is found
in the given range. But it is not a problem because there is very few
user that gives FOLL_CMA to get_user_pages().

Change-Id: Idcd651d5e2bc7ec66d17b3296e742b7e714f4b48
Signed-off-by: Cho KyongHo <pullip.cho@samsung.com>