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>

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index b556eef..1b0cd4c 100644 (file)
--- 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 0dd9ca1..c483c5c 100644 (file)
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -123,17 +123,15 @@ 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 dfe4055..171db51 100644 (file)
--- 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)