2 files changed, 17 insertions, 10 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index adcbfadfcb4c..d0d8c76c7edb 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));
diff --git a/include/linux/ext4_fs_sb.h b/include/linux/ext4_fs_sb.h
index 691a713139ce..2347557a327a 100644
--- a/include/linux/ext4_fs_sb.h
+++ b/include/linux/ext4_fs_sb.h
@@ -39,6 +39,8 @@ struct ext4_sb_info {
         unsigned long s_gdb_count;      /* Number of group descriptor blocks */
         unsigned long s_desc_per_block; /* Number of group descriptors per block */
         unsigned long s_groups_count;   /* Number of groups in the fs */
+        unsigned long s_overhead_last;  /* Last calculated overhead */
+        unsigned long s_blocks_last;    /* Last seen block count */
         struct buffer_head * s_sbh;     /* Buffer containing the super block */
         struct ext4_super_block * s_es; /* Pointer to the super block in the buffer */
         struct buffer_head ** s_group_desc;