Re: Far too long mount time

[Theodore Ts'o <tytso@mit.edu>]

On Thu, Aug 16, 2012 at 10:42:19AM -0400, Theodore Ts'o wrote:
> On Thu, Aug 16, 2012 at 10:16:48AM -0400, Calvin Walton wrote:
> > On Thu, 2012-08-16 at 03:09 -0600, Andreas Dilger wrote:
> > Is there any fix for this issue queued up for an upcoming stable
> > release? It still reverts cleanly on 3.5.2.
> 
> There isn't a fix queued up yet, but there will be one soon....

This patch should solve the problem (as an alternative to reverting
8aeb00ff85a).

						- Ted


>From dc43c7a8a6c266c31aa4f0408000c4d1b9f3c787 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Thu, 16 Aug 2012 11:59:04 -0400
Subject: [PATCH] ext4: fix long mount times on very big file systems

Commit 8aeb00ff85a: "ext4: fix overhead calculation used by
ext4_statfs()" introduced a O(n**2) calculation which makes very large
file systems take forever to mount.  Fix this with an optimization for
non-bigalloc file systems.  (For bigalloc file systems the overhead
needs to be set in the the superblock.)

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
---
 fs/ext4/super.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 603023b..055c65b 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3129,6 +3129,10 @@ static int count_overhead(struct super_block *sb, ext4_group_t grp,
 	ext4_group_t		i, ngroups = ext4_get_groups_count(sb);
 	int			s, j, count = 0;
 
+	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_BIGALLOC))
+		return (ext4_bg_has_super(sb, grp) + ext4_bg_num_gdb(sb, i) +
+			sbi->s_itb_per_group + 2);
+
 	first_block = le32_to_cpu(sbi->s_es->s_first_data_block) +
 		(grp * EXT4_BLOCKS_PER_GROUP(sb));
 	last_block = first_block + EXT4_BLOCKS_PER_GROUP(sb) - 1;
-- 
1.7.12.rc0.22.gcdd159b