Re: [PATCH AUTOSEL 5.11 26/44] btrfs: track qgroup released data in own variable in insert_prealloc_file_extent

[David Sterba]

On Thu, Mar 25, 2021 at 07:24:41AM -0400, Sasha Levin wrote:
> From: Qu Wenruo <wqu@xxxxxxxx>
> 
> [ Upstream commit fbf48bb0b197e6894a04c714728c952af7153bf3 ]
> 
> There is a piece of weird code in insert_prealloc_file_extent(), which
> looks like:
> 
> 	ret = btrfs_qgroup_release_data(inode, file_offset, len);
> 	if (ret < 0)
> 		return ERR_PTR(ret);
> 	if (trans) {
> 		ret = insert_reserved_file_extent(trans, inode,
> 						  file_offset, &stack_fi,
> 						  true, ret);
> 	...
> 	}
> 	extent_info.is_new_extent = true;
> 	extent_info.qgroup_reserved = ret;
> 	...
> 
> Note how the variable @ret is abused here, and if anyone is adding code
> just after btrfs_qgroup_release_data() call, it's super easy to
> overwrite the @ret and cause tons of qgroup related bugs.
> 
> Fix such abuse by introducing new variable @qgroup_released, so that we
> won't reuse the existing variable @ret.
> 
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> Reviewed-by: David Sterba <dsterba@xxxxxxxx>
> Signed-off-by: David Sterba <dsterba@xxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

This patch is a preparatory work and does not make sense for backport
standalone. Either this one plus
https://lore.kernel.org/linux-btrfs/20210303104152.105877-2-wqu@xxxxxxxx/
or neither. And IIRC it does not apply directly and needs some
additional review before it can be backported to older code base, so it
has no CC: stable tags.