Revert "vfs: Export file system uuid via /proc/<pid>/mountinfo"

This reverts commit 93f1c20b.

It turns out that libmount misparses it because it adds a '-' character
in the uuid string, which libmount then incorrectly confuses with the
separator string (" - ") at the end of all the optional arguments.

Upstream libmount (in the util-linux tree) has been fixed, but until
that fix actually percolates up to users, we'd better not expose this
change in the kernel.

Let's revisit this later (possibly by exposing the UUID without any '-'
characters in it, avoiding the user-space bug).
Reported-by: Dave Jones <davej@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Karel Zak <kzak@redhat.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Miklos Szeredi <mszeredi@suse.cz>
Cc: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/namespace.c

@@ -1030,18 +1030,6 @@ const struct seq_operations mounts_op = {
 	.show	= show_vfsmnt
 };
 
-static int uuid_is_nil(u8 *uuid)
-{
-	int i;
-	u8  *cp = (u8 *)uuid;
-
-	for (i = 0; i < 16; i++) {
-		if (*cp++)
-			return 0;
-	}
-	return 1;
-}
-
 static int show_mountinfo(struct seq_file *m, void *v)
 {
 	struct proc_mounts *p = m->private;
@@ -1085,10 +1073,6 @@ static int show_mountinfo(struct seq_file *m, void *v)
 	if (IS_MNT_UNBINDABLE(mnt))
 		seq_puts(m, " unbindable");
 
-	if (!uuid_is_nil(mnt->mnt_sb->s_uuid))
-		/* print the uuid */
-		seq_printf(m, " uuid:%pU", mnt->mnt_sb->s_uuid);
-
 	/* Filesystem specific data */
 	seq_puts(m, " - ");
 	show_type(m, sb);

include/linux/fs.h

@@ -1403,7 +1403,6 @@ struct super_block {
 	wait_queue_head_t	s_wait_unfrozen;
 
 	char s_id[32];				/* Informational name */
-	u8 s_uuid[16];				/* UUID */
 
 	void 			*s_fs_info;	/* Filesystem private info */
 	fmode_t			s_mode;