mm: make try_to_munlock() return void

try_to_munlock returns SWAP_MLOCK if the one of VMAs mapped the page has
VM_LOCKED flag.  In that time, VM set PG_mlocked to the page if the page
is not pte-mapped THP which cannot be mlocked, either.

With that, __munlock_isolated_page can use PageMlocked to check whether
try_to_munlock is successful or not without relying on try_to_munlock's
retval.  It helps to make try_to_unmap/try_to_unmap_one simple with
upcoming patches.

[minchan@kernel.org: remove PG_Mlocked VM_BUG_ON check]
  Link: http://lkml.kernel.org/r/20170411025615.GA6545@bbox
Link: http://lkml.kernel.org/r/1489555493-14659-5-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 12 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index dfe4055..171db51 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1552,18 +1552,10 @@ static int page_not_mapped(struct page *page)
  * Called from munlock code.  Checks all of the VMAs mapping the page
  * to make sure nobody else has this page mlocked. The page will be
  * returned with PG_mlocked cleared if no other vmas have it mlocked.
- *
- * Return values are:
- *
- * SWAP_AGAIN	- no vma is holding page mlocked, or,
- * SWAP_AGAIN	- page mapped in mlocked vma -- couldn't acquire mmap sem
- * SWAP_FAIL	- page cannot be located at present
- * SWAP_MLOCK	- page is now mlocked.
  */
-int try_to_munlock(struct page *page)
-{
-	int ret;
 
+void try_to_munlock(struct page *page)
+{
 	struct rmap_walk_control rwc = {
 		.rmap_one = try_to_unmap_one,
 		.arg = (void *)TTU_MUNLOCK,
@@ -1573,9 +1565,9 @@ int try_to_munlock(struct page *page)
 	};
 
 	VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
+	VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
 
-	ret = rmap_walk(page, &rwc);
-	return ret;
+	rmap_walk(page, &rwc);
 }
 
 void __put_anon_vma(struct anon_vma *anon_vma)