[0/3] block: align CoR requests to subclusters

Message

Andrey Drobyshev June 26, 2023, 4:08 p.m. UTC

This series makes IO requests performed with copy-on-read to be aligned
to subclusters rather than clusters.  It also affects mirror job requests
alignment.

The initial reason for that change is the following crash discovered:

qemu-img create -f qcow2 base.qcow2 64K
qemu-img create -f qcow2 -o extended_l2=on,backing_file=base.qcow2,backing_fmt=qcow2 img.qcow2 64K
qemu-io -c "write -P 0xaa 0 2K" img.qcow2
qemu-io -C -c "read -P 0x00 2K 62K" img.qcow2

qemu-io: ../block/io.c:1236: bdrv_co_do_copy_on_readv: Assertion `skip_bytes < pnum' failed.

This change in alignment fixes the crash and adds test case covering it.

Andrey Drobyshev (3):
  block: add subcluster_size field to BlockDriverInfo
  block/io: align requests to subcluster_size
  tests/qemu-iotests/197: add testcase for CoR with subclusters

 block.c                      |  6 +++++
 block/io.c                   | 50 ++++++++++++++++++------------------
 block/mirror.c               |  8 +++---
 block/qcow2.c                |  1 +
 include/block/block-common.h |  4 +++
 include/block/block-io.h     |  2 +-
 tests/qemu-iotests/197       | 29 +++++++++++++++++++++
 tests/qemu-iotests/197.out   | 24 +++++++++++++++++
 8 files changed, 94 insertions(+), 30 deletions(-)

Comments

Andrey Drobyshev July 7, 2023, 11:33 a.m. UTC | #1

On 6/26/23 19:08, Andrey Drobyshev wrote:
> This series makes IO requests performed with copy-on-read to be aligned
> to subclusters rather than clusters.  It also affects mirror job requests
> alignment.
> 
> The initial reason for that change is the following crash discovered:
> 
> qemu-img create -f qcow2 base.qcow2 64K
> qemu-img create -f qcow2 -o extended_l2=on,backing_file=base.qcow2,backing_fmt=qcow2 img.qcow2 64K
> qemu-io -c "write -P 0xaa 0 2K" img.qcow2
> qemu-io -C -c "read -P 0x00 2K 62K" img.qcow2
> 
> qemu-io: ../block/io.c:1236: bdrv_co_do_copy_on_readv: Assertion `skip_bytes < pnum' failed.
> 
> This change in alignment fixes the crash and adds test case covering it.
> 
> Andrey Drobyshev (3):
>   block: add subcluster_size field to BlockDriverInfo
>   block/io: align requests to subcluster_size
>   tests/qemu-iotests/197: add testcase for CoR with subclusters
> 
>  block.c                      |  6 +++++
>  block/io.c                   | 50 ++++++++++++++++++------------------
>  block/mirror.c               |  8 +++---
>  block/qcow2.c                |  1 +
>  include/block/block-common.h |  4 +++
>  include/block/block-io.h     |  2 +-
>  tests/qemu-iotests/197       | 29 +++++++++++++++++++++
>  tests/qemu-iotests/197.out   | 24 +++++++++++++++++
>  8 files changed, 94 insertions(+), 30 deletions(-)
> 

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