For btrfs it would be nice to exercise our subvol and snapshot operations with fsstress as well. The set of patches adds this ability. I've added a new file type for subvolumes, and they behave just like directories for all intents and purposes. The bulk of the supporting code needed for this went into the first patch, as well as the code to add the ability to link in libbtrfsutil. The second patch is more straightforward as it just adds the snapshot operation, and the final patch goes through and makes everybody pick either a directory or subvolume for their target file. I've done a bunch of testing with this on btrfs to make sure everything works as expected. I then did a follow up run on xfs to verify I didn't break the non-btrfs case. Thanks, Josef
