As per API, it just accepts the file fd but is it possible for this operation to accidentally flush the entire filesystem to disk?
For example, if the filesystem is journaling and I do fsync on this fd, could it just flush entire journal at which point all the files will be flushed (not just this one)?
I'm specifically interested to know how if the fsync(fd) may sync entire filesystem for ext4, zfs and btrfs.
