Re: [PATCH] btrfs: get the accurate value of used_bytes in btrfs_get_block_group_info().

[Dongsheng Yang <yangds.fnst@cn.fujitsu.com>]

Ping.....

IOCTL of BTRFS_IOC_SPACE_INFO currently does not report
the data used but not synced to user.  Then btrfs fi df will
give user a wrong numbers before sync. This patch solve
this problem.

On 10/27/2014 08:38 PM, Dongsheng Yang wrote:
> Reproducer:
> 	# mkfs.btrfs -f -b 20G /dev/sdb
> 	# mount /dev/sdb /mnt/test
> 	# fallocate  -l 17G /mnt/test/largefile
> 	# btrfs fi df /mnt/test
> 	Data, single: total=17.49GiB, used=6.00GiB <- only 6G, but actually it should be 17G.
> 	System, DUP: total=8.00MiB, used=16.00KiB
> 	System, single: total=4.00MiB, used=0.00B
> 	Metadata, DUP: total=1.00GiB, used=112.00KiB
> 	Metadata, single: total=8.00MiB, used=0.00B
> 	GlobalReserve, single: total=16.00MiB, used=0.00B
> 	# sync
> 	# btrfs fi df /mnt/test
> 	Data, single: total=17.49GiB, used=17.00GiB <- After sync, it is expected.
> 	System, DUP: total=8.00MiB, used=16.00KiB
> 	System, single: total=4.00MiB, used=0.00B
> 	Metadata, DUP: total=1.00GiB, used=112.00KiB
> 	Metadata, single: total=8.00MiB, used=0.00B
> 	GlobalReserve, single: total=16.00MiB, used=0.00B
>
> The value of 6.00GiB is actually calculated in btrfs_get_block_group_info()
> by adding the @block_group->item->used for each group together. In this way,
> it did not consider the bytes in cache.
>
> This patch adds the value of @pinned, @reserved and @bytes_super in
> struct btrfs_block_group_cache to make sure we can get the accurate @used_bytes.
>
> Reported-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
> ---
>   fs/btrfs/ioctl.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 33c80f5..bc2aaeb 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3892,6 +3892,10 @@ void btrfs_get_block_group_info(struct list_head *groups_list,
>   		space->total_bytes += block_group->key.offset;
>   		space->used_bytes +=
>   			btrfs_block_group_used(&block_group->item);
> +		/* Add bytes-info in cache */
> +		space->used_bytes += block_group->pinned;
> +		space->used_bytes += block_group->reserved;
> +		space->used_bytes += block_group->bytes_super;
>   	}
>   }
>