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

David Sterba
2020-08-27T11:35:03Z

On Fri, Jul 24, 2020 at 02:46:09PM +0800, 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>

Added to misc-next.

Patch 2/2 should go to stable (4.19+) but it does not apply even to 5.8
due to some other intermediate changes. I have tagged it for 4.19 but it
will expectedly fail to apply. A backport would be needed then.