[PATCH 5.2 72/85] mm/z3fold.c: remove z3fold_migration trylock

Greg Kroah-Hartman
2019-09-18T06:28:46Z

From: Henry Burns <henryburns@google.com>

commit be03074c9af25d06cf8e9ebddfcd284c0bf7f947 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/z3fold.c | 6 ------
1 file changed, 6 deletions(-)

--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -1439,16 +1439,11 @@ static int z3fold_page_migrate(struct ad
zhdr = page_address(page);
pool = zhdr_to_pool(zhdr);

- if (!trylock_page(page))
- return -EAGAIN;
-
if (!z3fold_page_trylock(zhdr)) {
- unlock_page(page);
return -EAGAIN;
}
if (zhdr->mapped_count != 0) {
z3fold_page_unlock(zhdr);
- unlock_page(page);
return -EBUSY;
}
if (work_pending(&zhdr->work)) {
@@ -1494,7 +1489,6 @@ static int z3fold_page_migrate(struct ad
spin_unlock(&pool->lock);

page_mapcount_reset(page);
- unlock_page(page);
put_page(page);
return 0;
}