efivarfs: Add unique magic number

Using pstore's superblock magic number is no doubt going to cause
problems in the future. Give efivarfs its own magic number.
Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

drivers/firmware/efivars.c

@@ -991,7 +991,7 @@ int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_maxbytes          = MAX_LFS_FILESIZE;
 	sb->s_blocksize         = PAGE_CACHE_SIZE;
 	sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
-	sb->s_magic             = PSTOREFS_MAGIC;
+	sb->s_magic             = EFIVARFS_MAGIC;
 	sb->s_op                = &efivarfs_ops;
 	sb->s_time_gran         = 1;
 

include/uapi/linux/magic.h

@@ -27,6 +27,7 @@
 #define ISOFS_SUPER_MAGIC	0x9660
 #define JFFS2_SUPER_MAGIC	0x72b6
 #define PSTOREFS_MAGIC		0x6165676C
+#define EFIVARFS_MAGIC		0xde5e81e4
 
 #define MINIX_SUPER_MAGIC	0x137F		/* minix v1 fs, 14 char names */
 #define MINIX_SUPER_MAGIC2	0x138F		/* minix v1 fs, 30 char names */