Re: [PATCH 1/2] btrfs: qgroup: fix wrong qgroup metadata reserve for delayed inode

[Josef Bacik <josef@toxicpanda.com>]

On 7/24/20 2:46 AM, Qu Wenruo wrote:
> For delayed inode facility, qgroup metadata is reserved for it, and
> later freed.
> 
> However we're freeing more bytes than we reserved.
> In btrfs_delayed_inode_reserve_metadata():
> 
> 	num_bytes = btrfs_calc_metadata_size(fs_info, 1);
> 	...
> 		ret = btrfs_qgroup_reserve_meta_prealloc(root,
> 				fs_info->nodesize, true);
> 		...
> 		if (!ret) {
> 			node->bytes_reserved = num_bytes;
> 
> But in btrfs_delayed_inode_release_metadata():
> 
> 	if (qgroup_free)
> 		btrfs_qgroup_free_meta_prealloc(node->root,
> 				node->bytes_reserved);
> 	else
> 		btrfs_qgroup_convert_reserved_meta(node->root,
> 				node->bytes_reserved);
> 
> This means, we're always releasing more qgroup metadata rsv than we have
> reserved.
> 
> This won't trigger selftest warning, as btrfs qgroup metadata rsv has
> extra protection against cases like quota enabled half-way.
> 
> But we still need to fix this problem any way.
> 
> This patch will use the same num_bytes for qgroup metadata rsv so we
> could handle it correctly.
> 
> Fixes: f218ea6c4792 ("btrfs: delayed-inode: Remove wrong qgroup meta reservation calls")
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef