(More) new code for 5.7: - Validate the realtime geometry in the superblock when mounting - Refactor a bunch of tricky flag handling in the log code - Flush the CIL more judiciously so that we don't wait until there are millions of log items consuming a lot of memory. - Throttle transaction commits to prevent the xfs frontend from flooding the CIL with too many log items. - Account metadata buffers correctly for memory reclaim. - Mark slabs properly for memory reclaim. These should help reclaim run more effectively when XFS is using a lot of memory. - Don't write a garbage log record at unmount time if we're trying to trigger summary counter recalculation at next mount. - Don't block the AIL on locked dquot/inode buffers; instead trigger its backoff mechanism to give the lock holder a chance to finish up. - Ratelimit writeback flushing when buffered writes encounter ENOSPC. - Other minor cleanups.