generic: add gc stress test

This test stresses garbage collection for file systems by first filling
up a scratch mount to a specific usage point with files of random size,
then doing overwrites in parallel with deletes to fragment the backing
storage, forcing reclaim.

Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>
2 files changed