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

[David Sterba <dsterba@suse.cz>]

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.