the >1Tb block issue

[Michael Tokarev <mjt@tls.msk.ru>]

I just re-verified it on current stable
qemu-kvm-0.12.4.  The issue is still here,
trivial to trigger.

  kvm-img create test.raw 1500G
  kvm ... \
   -drive file=test.raw,if=virtio

it fails right on the mkfs stage:

  mkfs.ext4 /dev/vdb
  Writing inode tables: end_request: I/O error, dev vdb, sector 3145727872
  Buffer I/O error on device vdb, logical block 393215984
  lost page write due to I/O error on vdb
  Buffer I/O error on device vdb, logical block 393215985
  ...
  Buffer I/O error on device vdb, logical block 393215993

After that it continues the mkfs process, but I doubt it will
produce a good filesystem.

So far, only virtio has this problem.  I tested with if=ide, it's
slower but it went much further without any error.  It's still
running, but at this rate it will run for some hours more ;)
At least it does not spew errors like the virtio case.

Unfortunately I don't have enough free space to test.  Yes the file
is sparse, but it grows quite fast when mkfs is running, and I'm
not sure the ~100Gb free space on the largest filesystem I have
will be enough for it...  but let's see.

/mjt

/mjt