f2fs: avoid reverse IO order for NODE and DATA

There is a data race between allocate_data_block() and f2fs_sbumit_page_mbio(),
which incur unnecessary reversed bio submission.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -766,6 +766,7 @@ struct f2fs_sb_info {
 	/* for bio operations */
 	struct f2fs_bio_info read_io;			/* for read bios */
 	struct f2fs_bio_info write_io[NR_PAGE_TYPE];	/* for write bios */
+	struct mutex wio_mutex[NODE + 1];	/* bio ordering for NODE/DATA */
 
 	/* for checkpoint */
 	struct f2fs_checkpoint *ckpt;		/* raw checkpoint pointer */

fs/f2fs/segment.c

@@ -1399,11 +1399,17 @@ static void do_write_page(struct f2fs_summary *sum, struct f2fs_io_info *fio)
 {
 	int type = __get_segment_type(fio->page, fio->type);
 
+	if (fio->type == NODE || fio->type == DATA)
+		mutex_lock(&fio->sbi->wio_mutex[fio->type]);
+
 	allocate_data_block(fio->sbi, fio->page, fio->old_blkaddr,
 					&fio->new_blkaddr, sum, type);
 
 	/* writeout dirty page into bdev */
 	f2fs_submit_page_mbio(fio);
+
+	if (fio->type == NODE || fio->type == DATA)
+		mutex_unlock(&fio->sbi->wio_mutex[fio->type]);
 }
 
 void write_meta_page(struct f2fs_sb_info *sbi, struct page *page)

fs/f2fs/super.c

@@ -1436,6 +1436,8 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
 
 	INIT_LIST_HEAD(&sbi->s_list);
 	mutex_init(&sbi->umount_mutex);
+	mutex_init(&sbi->wio_mutex[NODE]);
+	mutex_init(&sbi->wio_mutex[DATA]);
 
 #ifdef CONFIG_F2FS_FS_ENCRYPTION
 	memcpy(sbi->key_prefix, F2FS_KEY_DESC_PREFIX,