fs/fat: return f_fsid for statfs(2)

Make fat return f_fsid info for statfs(2).
Signed-off-by: Coly Li <coly.li@suse.de>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/fat/inode.c

@@ -523,7 +523,9 @@ static int fat_remount(struct super_block *sb, int *flags, char *data)
 
 static int fat_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
-	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
+	struct super_block *sb = dentry->d_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 
 	/* If the count of free cluster is still unknown, counts it here. */
 	if (sbi->free_clusters == -1 || !sbi->free_clus_valid) {
@@ -537,6 +539,8 @@ static int fat_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_blocks = sbi->max_cluster - FAT_START_ENT;
 	buf->f_bfree = sbi->free_clusters;
 	buf->f_bavail = sbi->free_clusters;
+	buf->f_fsid.val[0] = (u32)id;
+	buf->f_fsid.val[1] = (u32)(id >> 32);
 	buf->f_namelen = sbi->options.isvfat ? 260 : 12;
 
 	return 0;