Re: [PATCH] fs: btrfs: extent_map: removed unneeded variable

[Johannes Thumshirn]

On 29/06/2021 10:51, lijian_8010a29@xxxxxxx wrote:
> From: lijian <lijian@xxxxxxxxxx>
> 
> removed unneeded variable 'ret'.

Wouldn't it make more sense to return an error (-ENOENT??) in case
the em lookup fails and handle the error in btrfs_finish_ordered_io()
as this is the only caller of unpin_extent_cache()?

I've actually tripped over this a couple of times already when 
investigating extent map and ordered extent splitting problems
on zoned filesystems:

	em = lookup_extent_mapping(tree, start, len);
	WARN_ON(!em || em->start != start);

Maybe even turn this WARN_ON() into an ASSERT() when introducing proper
error handling, as we shouldn't really get there unless we have a logical
error.