Bug 854474

Description of problem:
do live migration with keeping write date to the floppy, after migration completed,floppy returns Input/output error.

Version-Release number of selected component (if applicable):
host info:
# uname -r && rpm -q qemu-kvm
2.6.32-303.el6.x86_64
qemu-kvm-0.12.1.2-2.307.el6.x86_64
guest info:
# uname -r
2.6.32-303.el6.x86_64

How reproducible:
100%

Steps to Reproduce:
1.boot VM with floppy disk.
eg:# /usr/libexec/qemu-kvm -M rhel6.3.0 -enable-kvm -m 2048 -smp 2,sockets=2,cores=1,threads=1 -usb -device usb-tablet,id=input0 -name virtual_blk_device_test -uuid `uuidgen` -drive file=/mnt/RHEL-Server-6.3-64-sluo.qcow2,format=qcow2,if=none,id=drive-disk,cache=none,werror=stop,rerror=stop,aio=native -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x3,drive=drive-disk,id=virtio_image,bootindex=1 -netdev tap,id=hostnet0,script=/etc/qemu-ifup -device virtio-net-pci,netdev=hostnet0,id=virtio-net-pci0,mac=98:3B:CB:2E:90:A8,bus=pci.0,addr=0x4 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 -serial unix:/tmp/ttyS0,server,nowait -vnc :1 -bios /usr/share/seabios/bios-pm.bin -boot menu=on -monitor stdio -drive file=/mnt/floppy.vfd,if=none,id=drive-fdc0-0-0,format=raw,cache=none -global isa-fdc.driveA=drive-fdc0-0-0
2.modprobe floppy and format the floppy disk with ext4 filesystem type.
3.mount it and write data to the floppy with script.
# mkdir /home/floppy
# cat script.sh 
mount /dev/fd0 -t ext4 /home/floppy
for((;;))
do
  echo hello > /home/floppy/file
  echo "========================"
  rm -fr /home/floppy/file
done
4.do live migration
(qemu) migrate -d tcp:$ip_addr:$port

Actual results:
1.after the step 4, migration finish successfully, but the floppy returns I/O error in loop, can not write date to floppy any more.
...
script.sh: line 4: echo: write error: Input/output error
========================
script.sh: line 4: echo: write error: Input/output error
========================
script.sh: line 4: echo: write error: Input/output error
========================
...

2.the logs from dmesg as following:
...
This should not happen!!  Data will be lost
floppy0: disk absent or changed during operation
end_request: I/O error, dev fd0, sector 18
EXT4-fs error (device fd0): ext4_find_entry: reading directory #2 offset 0
EXT4-fs (fd0): previous I/O error to superblock detected
floppy0: disk absent or changed during operation
end_request: I/O error, dev fd0, sector 2
floppy0: disk absent or changed during operation
end_request: I/O error, dev fd0, sector 44
floppy0: disk absent or changed during operation
end_request: I/O error, dev fd0, sector 16
EXT4-fs error (device fd0): ext4_read_block_bitmap: Cannot read block bitmap - block_group = 0, block_bitmap = 8
EXT4-fs (fd0): previous I/O error to superblock detected
floppy0: disk absent or changed during operation
end_request: I/O error, dev fd0, sector 2
EXT4-fs (fd0): delayed block allocation failed for inode 12 at logical offset 0 with max blocks 1 with error -5
...

Expected results:
after the migration, the floppy can be used and can continue write data to it without any error.

Additional info: