f2fs: avoid f2fs_lock_op for IPU writes

Currently, if we do get_node_of_data before f2fs_lock_op, there may be dead lock
as follows, where process A would be in infinite loop, and B will NOT be awaked.

Process A(cp):            Process B:
f2fs_lock_all(sbi)
                        get_dnode_of_data <---- lock dn.node_page
flush_nodes             f2fs_lock_op

So, this patch adds f2fs_trylock_op to avoid f2fs_lock_op done by IPU.

Signed-off-by: Hou Pengyang <houpengyang@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index fcada9d..3bc3676 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -312,7 +312,7 @@ static int __commit_inmem_pages(struct inode *inode,
 			fio.page = page;
 			fio.old_blkaddr = NULL_ADDR;
 			fio.encrypted_page = NULL;
-			fio.need_lock = false,
+			fio.need_lock = LOCK_DONE;
 			err = do_write_data_page(&fio);
 			if (err) {
 				unlock_page(page);