Re: [PATCH 1/7] btrfs: correctly model root qgroup rsv in convert

[Qu Wenruo <wqu@suse.com>]

在 2024/3/27 08:09, Boris Burkov 写道:
> We use add_root_meta_rsv and sub_root_meta_rsv to track prealloc and
> pertrans reservations for subvols when quotas are enabled. The convert
> function does not properly increment pertrans after decrementing
> prealloc, so the count is not accurate.
> 
> Note: we check that the fs is not read-only to mirror the logic in
> qgroup_convert_meta, which checks that before adding to the pertrans rsv.
> 
> Fixes: 8287475a2055 ("btrfs: qgroup: Use root::qgroup_meta_rsv_* to record qgroup meta reserved space")
> Signed-off-by: Boris Burkov <boris@bur.io>
> ---
>   fs/btrfs/qgroup.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index a8197e25192c..2cba6451d164 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -4492,6 +4492,8 @@ void btrfs_qgroup_convert_reserved_meta(struct btrfs_root *root, int num_bytes)
>   				      BTRFS_QGROUP_RSV_META_PREALLOC);
>   	trace_qgroup_meta_convert(root, num_bytes);
>   	qgroup_convert_meta(fs_info, root->root_key.objectid, num_bytes);
> +	if (!sb_rdonly(fs_info->sb))
> +		add_root_meta_rsv(root, num_bytes, BTRFS_QGROUP_RSV_META_PERTRANS);

Don't we already call qgroup_rsv_add() inside qgroup_convert_meta()?
This sounds like a double add here.

And if you have any example to show the problem in a more detailed way, 
it would be great help.

Thanks,
Qu
>   }
>   
>   /*