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ext4: teach ext4_statfs() to deal with clusters if bigalloc is enabled

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Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2011-09-09 19:00:51 -04:00
parent 24aaa8ef4e
commit f975d6bcc7
1 changed files with 24 additions and 13 deletions
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37
fs/ext4/super.c
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@ -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 */