[PATCH V2] ext4: include journal blocks in df overhead calcs

[Eric Sandeen <sandeen@redhat.com>]

To more accurately calculate overhead for "bsd" style
df reporting, we should count the journal blocks as
overhead as well.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Tested-by: Eric Whitney <enwlinux@gmail.com>
---

V2: I guess s_overhead _is_ in clusters, so do
that conversion after all.  Ted, if I'm wrong, you
can pick the other patch ;)

Editorial/soapbox:

TBH it's hard to keep track of what fields are
now stored as "clusters" not blocks . . .

Esp. when we do things like use local vars named "blk" -

	blks = count_overhead(sb, i, buf);

but count_overhead() returns *clusters*, so it's
really quite confusing to keep it all straight.

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 80928f7..b441daa 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3229,6 +3229,10 @@ int ext4_calculate_overhead(struct super_block *sb)
 			memset(buf, 0, PAGE_SIZE);
 		cond_resched();
 	}
+	/* Add the journal blocks as well */
+	if (sbi->s_journal)
+		overhead += EXT4_B2C(sbi, sbi->s_journal->j_maxlen);
+
 	sbi->s_overhead = overhead;
 	smp_wmb();
 	free_page((unsigned long) buf);