I'm completing Brokenthorn OS tutorial where I create a virtual floppy in Ubuntu using MSDOSFS command and then I make changes to this virtual floppy, like changing its MBR using DD command and copying and removing files, the problem is when I make some changes and then run it on Qemu, it doesn't detect changes and shows result as if I hadn't made any change to the floppy drive, but after running and exit qemu some times, it then starts showing me correct result. Why doesn't qemu detect changes immediately?
When you are finished updating / deleting / copying files you should use the umount command to unmount the directory when finished. That will ensure all the file updates are complete. At that point try running it in QEMU. My guess is that you are keeping the file system mounted while running QEMU. That can cause the type of problems you seem to be observing.