On 10/26/18 1:43 PM, Nikolay Borisov wrote:
> The first part of balance operation is to shrink every constituting
> device to ensure there is free space for chunk allocation.
A very useful thing to be able to do if there's no unallocated raw disk
space left, is use balance to rewrite some blockgroup into the free
space of other ones.
This does not need any raw space for a chunk allocation. Requiring so
makes it unneccesarily more complicated for users to fix the situation
they got in.
> However, the code
> has been buggy ever since its introduction since calculating the space to shrink
> the device by was bounded by 1 mb. Most likely the original intention was to
> have an upper bound of 1g and not 1m, since the largest chunk size is 1g. This
> means the first stage in __btrfs_balance so far has been a null op since it
> effectively freed just a single megabyte.
>
> Fix this by setting an upper bound of size_to_free of 1g.
>
> Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
> ---
> fs/btrfs/volumes.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index f435d397019e..8b0fd7bf3447 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -3467,7 +3467,7 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
> list_for_each_entry(device, devices, dev_list) {
> old_size = btrfs_device_get_total_bytes(device);
> size_to_free = div_factor(old_size, 1);
> - size_to_free = min_t(u64, size_to_free, SZ_1M);
> + size_to_free = min_t(u64, size_to_free, SZ_1G);
> if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) ||
> btrfs_device_get_total_bytes(device) -
> btrfs_device_get_bytes_used(device) > size_to_free ||
>
--
Hans van Kranenburg
