[RFC 05/11] mm: make the try_to_munlock void function

Minchan Kim
2017-03-02T06:39:32Z

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 ttu/ttuo simple with
upcoming patches.

Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
include/linux/rmap.h | 2 +-
mm/mlock.c | 6 ++----
mm/rmap.c | 16 ++++------------
3 files changed, 7 insertions(+), 17 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index b556eef..1b0cd4c 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -235,7 +235,7 @@ int page_mkclean(struct page *);
* called in munlock()/munmap() path to check for other vmas holding
* the page mlocked.
*/
-int try_to_munlock(struct page *);
+void try_to_munlock(struct page *);

void remove_migration_ptes(struct page *old, struct page *new, bool locked);

diff --git a/mm/mlock.c b/mm/mlock.c
index cdbed8a..d34a540 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -122,17 +122,15 @@ static bool __munlock_isolate_lru_page(struct page *page, bool getpage)
*/
static void __munlock_isolated_page(struct page *page)
{
- int ret = SWAP_AGAIN;
-
/*
* Optimization: if the page was mapped just once, that's our mapping
* and we don't need to check all the other vmas.
*/
if (page_mapcount(page) > 1)
- ret = try_to_munlock(page);
+ try_to_munlock(page);

/* Did try_to_unlock() succeed or punt? */
- if (ret != SWAP_MLOCK)
+ if (!PageMlocked(page))
count_vm_event(UNEVICTABLE_PGMUNLOCKED);

putback_lru_page(page);
diff --git a/mm/rmap.c b/mm/rmap.c
index 0a48958..61ae694 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1540,18 +1540,10 @@ 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,
@@ -1561,9 +1553,9 @@ int try_to_munlock(struct page *page)
};

VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
+ VM_BUG_ON_PAGE(PageMlocked(page), page);

- ret = rmap_walk(page, &rwc);
- return ret;
+ rmap_walk(page, &rwc);
}

void __put_anon_vma(struct anon_vma *anon_vma)
--
2.7.4