diff options
| -rw-r--r-- | fs/ext4/super.c | 37 |
1 files changed, 24 insertions, 13 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index d7e0e04..6810957 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4580,16 +4580,34 @@ restore_opts: return err; } +/* + * Note: calculating the overhead so we can be compatible with + * historical BSD practice is quite difficult in the face of + * clusters/bigalloc. This is because multiple metadata blocks from + * different block group can end up in the same allocation cluster. + * Calculating the exact overhead in the face of clustered allocation + * requires either O(all block bitmaps) in memory or O(number of block + * groups**2) in time. We will still calculate the superblock for + * older file systems --- and if we come across with a bigalloc file + * system with zero in s_overhead_clusters the estimate will be close to + * correct especially for very large cluster sizes --- but for newer + * file systems, it's better to calculate this figure once at mkfs + * time, and store it in the superblock. If the superblock value is + * present (even for non-bigalloc file systems), we will use it. + */ 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; + struct ext4_group_desc *gdp; u64 fsid; s64 bfree; if (test_opt(sb, MINIX_DF)) { sbi->s_overhead_last = 0; + } else if (es->s_overhead_clusters) { + sbi->s_overhead_last = le32_to_cpu(es->s_overhead_clusters); } else if (sbi->s_blocks_last != ext4_blocks_count(es)) { ext4_group_t i, ngroups = ext4_get_groups_count(sb); ext4_fsblk_t overhead = 0; @@ -4604,24 +4622,16 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf) * All of the blocks before first_data_block are * overhead */ - overhead = le32_to_cpu(es->s_first_data_block); + overhead = EXT4_B2C(sbi, le32_to_cpu(es->s_first_data_block)); /* - * Add the overhead attributed to the superblock and - * block group descriptors. If the sparse superblocks - * feature is turned on, then not all groups have this. + * Add the overhead found in each block group */ for (i = 0; i < ngroups; i++) { - overhead += ext4_bg_has_super(sb, i) + - ext4_bg_num_gdb(sb, i); + gdp = ext4_get_group_desc(sb, i, NULL); + overhead += ext4_num_overhead_clusters(sb, i, gdp); cond_resched(); } - - /* - * Every block group has an inode bitmap, a block - * bitmap, and an inode table. - */ - overhead += ngroups * (2 + sbi->s_itb_per_group); sbi->s_overhead_last = overhead; smp_wmb(); sbi->s_blocks_last = ext4_blocks_count(es); @@ -4629,7 +4639,8 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf) buf->f_type = EXT4_SUPER_MAGIC; buf->f_bsize = sb->s_blocksize; - buf->f_blocks = ext4_blocks_count(es) - sbi->s_overhead_last; + buf->f_blocks = (ext4_blocks_count(es) - + EXT4_C2B(sbi, sbi->s_overhead_last)); bfree = percpu_counter_sum_positive(&sbi->s_freeclusters_counter) - percpu_counter_sum_positive(&sbi->s_dirtyclusters_counter); /* prevent underflow in case that few free space is available */ |
