1 files changed, 45 insertions, 6 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 8e16bca69c56..18cdcd1dbe11 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1672,6 +1672,21 @@ static int btrfs_calc_avail_data_space(struct btrfs_root *root, u64 *free_bytes)
 	return 0;
 }
 
+/*
+ * Calculate numbers for 'df', pessimistic in case of mixed raid profiles.
+ *
+ * If there's a redundant raid level at DATA block groups, use the respective
+ * multiplier to scale the sizes.
+ *
+ * Unused device space usage is based on simulating the chunk allocator
+ * algorithm that respects the device sizes, order of allocations and the
+ * 'alloc_start' value, this is a close approximation of the actual use but
+ * there are other factors that may change the result (like a new metadata
+ * chunk).
+ *
+ * FIXME: not accurate for mixed block groups, total and free/used are ok,
+ * available appears slightly larger.
+ */
 static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(dentry->d_sb);
@@ -1682,6 +1697,8 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	u64 total_free_data = 0;
 	int bits = dentry->d_sb->s_blocksize_bits;
 	__be32 *fsid = (__be32 *)fs_info->fsid;
+	unsigned factor = 1;
+	struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv;
 	int ret;
 
 	/* holding chunk_muext to avoid allocating new chunks */
@@ -1689,30 +1706,52 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	rcu_read_lock();
 	list_for_each_entry_rcu(found, head, list) {
 		if (found->flags & BTRFS_BLOCK_GROUP_DATA) {
+			int i;
+
 			total_free_data += found->disk_total - found->disk_used;
 			total_free_data -=
 				btrfs_account_ro_block_groups_free_space(found);
+
+			for (i = 0; i < BTRFS_NR_RAID_TYPES; i++) {
+				if (!list_empty(&found->block_groups[i])) {
+					switch (i) {
+					case BTRFS_RAID_DUP:
+					case BTRFS_RAID_RAID1:
+					case BTRFS_RAID_RAID10:
+						factor = 2;
+					}
+				}
+			}
 		}
 
 		total_used += found->disk_used;
 	}
+
 	rcu_read_unlock();
 
-	buf->f_namelen = BTRFS_NAME_LEN;
-	buf->f_blocks = btrfs_super_total_bytes(disk_super) >> bits;
-	buf->f_bfree = buf->f_blocks - (total_used >> bits);
-	buf->f_bsize = dentry->d_sb->s_blocksize;
-	buf->f_type = BTRFS_SUPER_MAGIC;
+	buf->f_blocks = div_u64(btrfs_super_total_bytes(disk_super), factor);
+	buf->f_blocks >>= bits;
+	buf->f_bfree = buf->f_blocks - (div_u64(total_used, factor) >> bits);
+
+	/* Account global block reserve as used, it's in logical size already */
+	spin_lock(&block_rsv->lock);
+	buf->f_bfree -= block_rsv->size >> bits;
+	spin_unlock(&block_rsv->lock);
+
 	buf->f_bavail = total_free_data;
 	ret = btrfs_calc_avail_data_space(fs_info->tree_root, &total_free_data);
 	if (ret) {
 		mutex_unlock(&fs_info->chunk_mutex);
 		return ret;
 	}
-	buf->f_bavail += total_free_data;
+	buf->f_bavail += div_u64(total_free_data, factor);
 	buf->f_bavail = buf->f_bavail >> bits;
 	mutex_unlock(&fs_info->chunk_mutex);
 
+	buf->f_type = BTRFS_SUPER_MAGIC;
+	buf->f_bsize = dentry->d_sb->s_blocksize;
+	buf->f_namelen = BTRFS_NAME_LEN;
+
 	/* We treat it as constant endianness (it doesn't matter _which_)
 	   because we want the fsid to come out the same whether mounted
 	   on a big-endian or little-endian host */