1 files changed, 15 insertions, 10 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index adcbfad..d0d8c76 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2500,19 +2500,19 @@ static int ext4_statfs (struct dentry * dentry, struct kstatfs * buf)
 	struct super_block *sb = dentry->d_sb;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct ext4_super_block *es = sbi->s_es;
-	ext4_fsblk_t overhead;
-	int i;
 	u64 fsid;
 
-	if (test_opt (sb, MINIX_DF))
-		overhead = 0;
-	else {
-		unsigned long ngroups;
-		ngroups = EXT4_SB(sb)->s_groups_count;
+	if (test_opt(sb, MINIX_DF)) {
+		sbi->s_overhead_last = 0;
+	} else if (sbi->s_blocks_last != le32_to_cpu(es->s_blocks_count)) {
+		unsigned long ngroups = sbi->s_groups_count, i;
+		ext4_fsblk_t overhead = 0;
 		smp_rmb();
 
 		/*
-		 * Compute the overhead (FS structures)
+		 * Compute the overhead (FS structures).  This is constant
+		 * for a given filesystem unless the number of block groups
+		 * changes so we cache the previous value until it does.
 		 */
 
 		/*
@@ -2536,18 +2536,23 @@ static int ext4_statfs (struct dentry * dentry, struct kstatfs * buf)
 		 * Every block group has an inode bitmap, a block
 		 * bitmap, and an inode table.
 		 */
-		overhead += (ngroups * (2 + EXT4_SB(sb)->s_itb_per_group));
+		overhead += ngroups * (2 + sbi->s_itb_per_group);
+		sbi->s_overhead_last = overhead;
+		smp_wmb();
+		sbi->s_blocks_last = le32_to_cpu(es->s_blocks_count);
 	}
 
 	buf->f_type = EXT4_SUPER_MAGIC;
 	buf->f_bsize = sb->s_blocksize;
-	buf->f_blocks = ext4_blocks_count(es) - overhead;
+	buf->f_blocks = ext4_blocks_count(es) - sbi->s_overhead_last;
 	buf->f_bfree = percpu_counter_sum(&sbi->s_freeblocks_counter);
+	es->s_free_blocks_count = cpu_to_le32(buf->f_bfree);
 	buf->f_bavail = buf->f_bfree - ext4_r_blocks_count(es);
 	if (buf->f_bfree < ext4_r_blocks_count(es))
 		buf->f_bavail = 0;
 	buf->f_files = le32_to_cpu(es->s_inodes_count);
 	buf->f_ffree = percpu_counter_sum(&sbi->s_freeinodes_counter);
+	es->s_free_inodes_count = cpu_to_le32(buf->f_ffree);
 	buf->f_namelen = EXT4_NAME_LEN;
 	fsid = le64_to_cpup((void *)es->s_uuid) ^
 	       le64_to_cpup((void *)es->s_uuid + sizeof(u64));