mm, thp: fix mapped pages avoiding unevictable list on mlock

[Simon Jeons <simon.jeons@xxxxxxxxx>]

Hi David,

http://marc.info/?l=linux-mm&m=134810397323814&w=2

	#define MAP_SIZE	(4 << 30)	/* 4GB */

	void *ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE,
			 MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
	mlock(ptr, MAP_SIZE);

		$ grep -E "Unevictable|Inactive\(anon" /proc/meminfo
		Inactive(anon):     6304 kB
		Unevictable:     4213924 kB                          

These pages are allocated in mlock path(gup), correct? If the answer is yes, follow_page also will not set these pages unevictable, is it? Then how you get these pages unevictable?


	munlock(ptr, MAP_SIZE);

		Inactive(anon):  4186252 kB
		Unevictable:       19652 kB

	mlock(ptr, MAP_SIZE);

		Inactive(anon):  4198556 kB
		Unevictable:       21684 kB