Following zsmalloc.c's example we call trylock_page() and unlock_page(). Also make z3fold_page_migrate() assert that newpage is passed in locked, as per the documentation.

Link: http://lkml.kernel.org/r/20190702005122.41036-1-henryburns@google.com Signed-off-by: Henry Burns henryburns@google.com Suggested-by: Vitaly Wool vitalywool@gmail.com Acked-by: Vitaly Wool vitalywool@gmail.com Acked-by: David Rientjes rientjes@google.com Cc: Shakeel Butt shakeelb@google.com Cc: Vitaly Vul vitaly.vul@sony.com Cc: Mike Rapoport rppt@linux.vnet.ibm.com Cc: Xidong Wang wangxidong_97@163.com Cc: Jonathan Adams jwadams@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org --- Changelog since v2: - Removed the WARN_ON entirely, as it is an expected code path.

Changelog since v1: - Added an if statement around WARN_ON(trylock_page(page)) to avoid unlocking a page locked by a someone else.

mm/z3fold.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/mm/z3fold.c b/mm/z3fold.c index e174d1549734..eeb3fe7f5ca3 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -918,7 +918,16 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, set_bit(PAGE_HEADLESS, &page->private); goto headless; } - __SetPageMovable(page, pool->inode->i_mapping); + if (can_sleep) { + lock_page(page); + __SetPageMovable(page, pool->inode->i_mapping); + unlock_page(page); + } else { + if (!trylock_page(page)) { + __SetPageMovable(page, pool->inode->i_mapping); + unlock_page(page); + } + } z3fold_page_lock(zhdr);

found: @@ -1325,6 +1334,7 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa

VM_BUG_ON_PAGE(!PageMovable(page), page); VM_BUG_ON_PAGE(!PageIsolated(page), page); + VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);

zhdr = page_address(page); pool = zhdr_to_pool(zhdr);