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

We add a per superblock uuid field. File systems should
update the uuid in the fill_super callback

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 17 insertions, 0 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index d1edf26025dc..dffe6f49ab93 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1002,6 +1002,18 @@ 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;
@@ -1040,6 +1052,10 @@ 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);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3f64630c0e10..f2143e0942c2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1408,6 +1408,7 @@ 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;