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qemu-nbd corrupts files
Dear all,
On Trusty, in certain situations, try to copy files over a qemu-nbd mounted file system leads to write errors (and thus, file corruption).
Here is the last example I tried:
-> virtual disk is a VDI disk
-> It has only one partition, in FAT
Here is my mount process:
# modprobe nbd max_part=63
# qemu-nbd -c /dev/nbd0 "virtual_disk.vdi"
# partprobe /dev/nbd0
# mount /dev/nbd0p1 /tmp/mnt/
Partition is properly mounted at that point:
/dev/nbd0p1 on /tmp/mnt type vfat (rw)
Now, when I copy a file (rather big, ~28MB):
# cp file_to_copy /tmp/mnt/ ; sync
# md5sum /tmp/mnt/file_to_copy
2efc9f32e4267782b11d63d2f128a363 /tmp/mnt/file_to_copy
# umount /tmp/mnt
# mount /dev/nbd0p1 /tmp/mnt/
# md5sum /tmp/mnt/file_to_copy
42b0a3bf73f704d03ce301716d7654de /tmp/mnt/file_to_copy
The first hash was obviously the right one.
On a previous attempt I did, I spotted thanks to vbindiff that parts of the file were just filed with 0s instead of actual data.
It will randomly work after several attempts to write.
Version information:
# qemu-nbd --version
qemu-nbd version 0.0.1
Written by Anthony Liguori.
Cheers,
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