Garbage collection for a log-structured file system can be offloaded from a processor to an internal controller of a storage device, such as a solid-state drive. For example, an internal controller of a storage device can determine characteristics of a log-structured file system hosted by a processor that is external to the storage device. The characteristics can indicate how data is arranged in the log-structured file system. The internal controller can then execute, based on the characteristics, a garbage collection process with respect to the data of the log-structured file system on behalf of the processor.