fat: Hook up sb->s_uuid

Now that we have a standard ioctl for querying the filesystem UUID,
initialize sb->s_uuid so that it works.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Link: https://lore.kernel.org/r/20240207025624.1019754-5-kent.overstreet@linux.dev
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Kent Overstreet

fs/fat/inode.c

@@ -1762,6 +1762,9 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
 	else /* fat 16 or 12 */
 		sbi->vol_id = bpb.fat16_vol_id;
 
+	__le32 vol_id_le = cpu_to_le32(sbi->vol_id);
+	super_set_uuid(sb, (void *) &vol_id_le, sizeof(vol_id_le));
+
 	sbi->dir_per_block = sb->s_blocksize / sizeof(struct msdos_dir_entry);
 	sbi->dir_per_block_bits = ffs(sbi->dir_per_block) - 1;