[PATCH] ext4: fsid for statvfs

Update ext4_statfs to return an FSID that is a 64 bit XOR of the 128 bit
filesystem UUID as suggested by Andreas Dilger.  See the following Bugzilla
entry for details:

  http://bugzilla.kernel.org/show_bug.cgi?id=136

Cc: Andreas Dilger <adilger@clusterfs.com>
Cc: Stephen Tweedie <sct@redhat.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index f2e8c4aa0fd2..2ede7e2c7019 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2460,6 +2460,7 @@ static int ext4_statfs (struct dentry * dentry, struct kstatfs * buf)
         struct ext4_super_block *es = sbi->s_es;
         ext4_fsblk_t overhead;
         int i;
+        u64 fsid;
 
         if (test_opt (sb, MINIX_DF))
                 overhead = 0;
@@ -2506,6 +2507,10 @@ static int ext4_statfs (struct dentry * dentry, struct kstatfs * buf)
         buf->f_files = le32_to_cpu(es->s_inodes_count);
         buf->f_ffree = percpu_counter_sum(&sbi->s_freeinodes_counter);
         buf->f_namelen = EXT4_NAME_LEN;
+        fsid = le64_to_cpup((void *)es->s_uuid) ^
+               le64_to_cpup((void *)es->s_uuid + sizeof(u64));
+        buf->f_fsid.val[0] = fsid & 0xFFFFFFFFUL;
+        buf->f_fsid.val[1] = (fsid >> 32) & 0xFFFFFFFFUL;
         return 0;
 }