[Qemu-block] [PATCH for-4.0? 0/2] Fix overflow bug in qcow2 discard

[Vladimir Sementsov-Ogievskiy]

Hi all. We faced an interesting bug, which may be simply reproduced:

prepare image:
./qemu-img create -f qcow2 -o cluster_size=1M /ssd/test 2300M
./qemu-io -c 'write 100M 2000M' -c 'write 2100M 200M' -c 'write 0 100M' 
/ssd/test

shrink:
./qemu-img resize --shrink /ssd/test 50M

bug:
./qemu-img info /ssd/test
image: /ssd/test
file format: qcow2
virtual size: 50M (52428800 bytes)
disk size: 2.2G
cluster_size: 1048576
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

Virtual size is shrunk, but file - not. It is due to the fact,
that merged qcow2 discard may exceed 2G, and then converting from
uint64_t to int in qcow2_process_discards when we call bdrv_pdiscard
make wrong thing.

So, here are proposal of fix and new iotest for it.

Vladimir Sementsov-Ogievskiy (2):
  block/io: bdrv_pdiscard: support int64_t bytes parameter
  iotests: test big qcow2 shrink

 include/block/block.h      |  4 +--
 block/io.c                 | 19 ++++++-----
 tests/qemu-iotests/249     | 69 ++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/249.out | 30 +++++++++++++++++
 tests/qemu-iotests/group   |  1 +
 5 files changed, 112 insertions(+), 11 deletions(-)
 create mode 100755 tests/qemu-iotests/249
 create mode 100644 tests/qemu-iotests/249.out

-- 
2.18.0