hfsplus: fix bless ioctl when used with hardlinks

HFS+ doesn't really implement hard links - instead, hardlinks are indicated
by a magic file type which refers to an indirect node in a hidden
directory. The spec indicates that stat() should return the inode number
of the indirect node, but it turns out that this doesn't satisfy the
firmware when it's looking for a bootloader - it wants the catalog ID of
the hardlink file instead. Fix up this case.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/hfsplus/ioctl.c

@@ -31,6 +31,7 @@ static int hfsplus_ioctl_bless(struct file *file, int __user *user_flags)
 	struct hfsplus_sb_info *sbi = HFSPLUS_SB(inode->i_sb);
 	struct hfsplus_vh *vh = sbi->s_vhdr;
 	struct hfsplus_vh *bvh = sbi->s_backup_vhdr;
+	u32 cnid = (unsigned long)dentry->d_fsdata;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -41,8 +42,12 @@ static int hfsplus_ioctl_bless(struct file *file, int __user *user_flags)
 	vh->finder_info[0] = bvh->finder_info[0] =
 		cpu_to_be32(parent_ino(dentry));
 
-	/* Bootloader */
-	vh->finder_info[1] = bvh->finder_info[1] = cpu_to_be32(inode->i_ino);
+	/*
+	 * Bootloader. Just using the inode here breaks in the case of
+	 * hard links - the firmware wants the ID of the hard link file,
+	 * but the inode points at the indirect inode
+	 */
+	vh->finder_info[1] = bvh->finder_info[1] = cpu_to_be32(cnid);
 
 	/* Per spec, the OS X system folder - same as finder_info[0] here */
 	vh->finder_info[5] = bvh->finder_info[5] =