Re: [PATCH] Btrfs: fix warning of free_extent_map

[Chris Mason <chris.mason@fusionio.com>]

Quoting Liu Bo (2013-03-15 10:46:39)
> Users report that an extent map's list is still linked when it's actually
> going to be freed from cache.
> 
> The story is that
> 
> a) when we're going to drop an extent map and may split this large one into
> smaller ems, and if this large one is flagged as EXTENT_FLAG_LOGGING which means
> that it's on the list to be logged, then the smaller ems split from it will also
> be flagged as EXTENT_FLAG_LOGGING, and this is _not_ expected.
> 
> b) we'll keep ems from unlinking the list and freeing when they are flagged with
> EXTENT_FLAG_LOGGING, because the log code holds one reference.
> 
> The end result is the warning, but the truth is that we set the flag
> EXTENT_FLAG_LOGGING only during fsync.
> 
> So clear flag EXTENT_FLAG_LOGGING for extent maps split from a large one.

Thanks for tracking this down!  I've got it in my tree now.

-chris