f2fs: fix to update F2FS_{CP_}WB_DATA count correctly

We should only account F2FS_{CP_}WB_DATA IOs for write path, fix it.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -398,7 +398,8 @@ int f2fs_submit_page_mbio(struct f2fs_io_info *fio)
 		if ((fio->type == DATA || fio->type == NODE) &&
 				fio->new_blkaddr & F2FS_IO_SIZE_MASK(sbi)) {
 			err = -EAGAIN;
-			dec_page_count(sbi, WB_DATA_TYPE(bio_page));
+			if (!is_read)
+				dec_page_count(sbi, WB_DATA_TYPE(bio_page));
 			goto out_fail;
 		}
 		io->bio = __bio_alloc(sbi, fio->new_blkaddr,