mm/mempolicy.c: fix pgoff in mbind vma merge
mm/mempolicy.c: fix pgoff in mbind vma merge

commit 9d8cebd4bcd7 ("mm: fix mbind vma merge problem") didn't really
fix the mbind vma merge problem due to wrong pgoff value passing to
vma_merge(), which made vma_merge() always return NULL.

Before the patch applied, we are getting a result like:

  addr = 0x7fa58f00c000
  [snip]
  7fa58f00c000-7fa58f00d000 rw-p 00000000 00:00 0
  7fa58f00d000-7fa58f00e000 rw-p 00000000 00:00 0
  7fa58f00e000-7fa58f00f000 rw-p 00000000 00:00 0

here 7fa58f00c000->7fa58f00f000 we get 3 VMAs which are expected to be
merged described as described in commit 9d8cebd.

Re-testing the patched kernel with the reproducer provided in commit
9d8cebd, we get the correct result:

  addr = 0x7ffa5aaa2000
  [snip]
  7ffa5aaa2000-7ffa5aaa6000 rw-p 00000000 00:00 0
  7fffd556f000-7fffd5584000 rw-p 00000000 00:00 0                          [stack]

Signed-off-by: Caspar Zhang <e1684cb1e6dd75540c0b8a5e3ba322ff3af30c24@casparzhang.com>
Cc: KOSAKI Motohiro <70a1d3ef3e17a2bb0f09a1b2e6c86f607ed1d6d9@jp.fujitsu.com>
Cc: Christoph Lameter <ef3ecccf258fa062c5c6521a4887d40541963af7@linux-foundation.org>
Cc: Hugh Dickins <a96f0e3e09e76642c8a5dcf04c8f12accf315063@tiscali.co.uk>
Cc: Mel Gorman <2f629c4d93e35c3d371f0463b040c6ef04a5c1e5@csn.ul.ie>
Cc: Lee Schermerhorn <f13429585ed8ee5cbbe1602189e3a516c4ea39be@hp.com>
Cc: Minchan Kim <12330474acf818c36105a159b1ab0efedce0665c@gmail.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs