From: Eric Sandeen <sandeen@redhat.com>
Subject: [PATCH] ext4: don't count external journal blocks as overhead
Date: Fri, 14 Nov 2014 12:39:47 -0600
Message-ID: <54664C73.60409@redhat.com>
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To: ext4 development <linux-ext4@vger.kernel.org>
Sender: linux-ext4-owner@vger.kernel.org

This was fixed for ext3 with:

e6d8fb3 ext3: Count internal journal as bsddf overhead in ext3_statfs

but was never fixed for ext4.

With a large external journal and no used disk blocks, df comes
out negative without this, as journal blocks are added to the
overhead & subtracted from used blocks unconditionally.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

ps: since this is stored in the on-disk superblock now, I'm not
sure how to fix up old filesystems, or if it matters much.

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 2c9e686..9674578 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3338,8 +3338,8 @@ 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)
+	/* Add the internal journal blocks as well */
+	if (sbi->s_journal && !sbi->journal_bdev)
 		overhead += EXT4_NUM_B2C(sbi, sbi->s_journal->j_maxlen);
 
 	sbi->s_overhead = overhead;