tmpfs: generate random sb->s_uuid

This is used by overlayfs to encode intrasystem unique file handles.

Suggested-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/mm/shmem.c b/mm/shmem.c
index e67d6ba4e98e73210c8046e82612180fca220e89..391f2dcca72782051cf2dfc5b71b7af11c73f2c9 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -75,6 +75,7 @@ static struct vfsmount *shm_mnt;
 #include <uapi/linux/memfd.h>
 #include <linux/userfaultfd_k.h>
 #include <linux/rmap.h>
+#include <linux/uuid.h>
 
 #include <linux/uaccess.h>
 #include <asm/pgtable.h>
@@ -3761,6 +3762,7 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent)
 #ifdef CONFIG_TMPFS_POSIX_ACL
        sb->s_flags |= MS_POSIXACL;
 #endif
+       uuid_gen(&sb->s_uuid);
 
        inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
        if (!inode)