mm/z3fold.c: remove z3fold_migration trylock

z3fold_page_migrate() will never succeed because it attempts to acquire
a lock that has already been taken by migrate.c in __unmap_and_move().

  __unmap_and_move() migrate.c
    trylock_page(oldpage)
    move_to_new_page(oldpage_newpage)
      a_ops->migrate_page(oldpage, newpage)
        z3fold_page_migrate(oldpage, newpage)
          trylock_page(oldpage)

Link: http://lkml.kernel.org/r/20190710213238.91835-1-henryburns@google.com
Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Snild Dolkow <snild@sony.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/z3fold.c b/mm/z3fold.c
index e13c622..70008a8 100644 (file)
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -1350,16 +1350,11 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
        zhdr = page_address(page);
        pool = zhdr_to_pool(zhdr);
 
        zhdr = page_address(page);
        pool = zhdr_to_pool(zhdr);
 

-       if (!trylock_page(page))
-               return -EAGAIN;
-

        if (!z3fold_page_trylock(zhdr)) {
        if (!z3fold_page_trylock(zhdr)) {

-               unlock_page(page);

                return -EAGAIN;
        }
        if (zhdr->mapped_count != 0) {
                z3fold_page_unlock(zhdr);
                return -EAGAIN;
        }
        if (zhdr->mapped_count != 0) {
                z3fold_page_unlock(zhdr);

-               unlock_page(page);

                return -EBUSY;
        }
        new_zhdr = page_address(newpage);
                return -EBUSY;
        }
        new_zhdr = page_address(newpage);


@@ -1391,7 +1386,6 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
        queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
 
        page_mapcount_reset(page);
        queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
 
        page_mapcount_reset(page);

-       unlock_page(page);

        put_page(page);
        return 0;
 }
        put_page(page);
        return 0;
 }