Re: [PATCH v5 0/9] block: Add retry for werror=/rerror= mechanism

[Jiahui Cen]

Kindly ping.
Any comments and reviews are wellcome :)

Thanks,
Jiahui

On 2021/2/5 18:13, Jiahui Cen wrote:
> A VM in the cloud environment may use a virutal disk as the backend storage,
> and there are usually filesystems on the virtual block device. When backend
> storage is temporarily down, any I/O issued to the virtual block device
> will cause an error. For example, an error occurred in ext4 filesystem would
> make the filesystem readonly. In production environment, a cloud backend
> storage can be soon recovered. For example, an IP-SAN may be down due to
> network failure and will be online soon after network is recovered. However,
> the error in the filesystem may not be recovered unless a device reattach
> or system restart. Thus an I/O retry mechanism is in need to implement a
> self-healing system.
> 
> This patch series propose to extend the werror=/rerror= mechanism to add
> a 'retry' feature. It can automatically retry failed I/O requests on error
> without sending error back to guest, and guest can get back running smoothly
> when I/O is recovred.
> 
> v4->v5:
> * Add document for 'retry' in qapi.
> * Support werror=/rerror=retry for scsi-disk.
> * Pause retry when draining.
> 
> v3->v4:
> * Adapt to werror=/rerror= mechanism.
> 
> v2->v3:
> * Add a doc to describe I/O hang.
> 
> v1->v2:
> * Rebase to fix compile problems.
> * Fix incorrect remove of rehandle list.
> * Provide rehandle pause interface.
> 
> REF: https://lists.gnu.org/archive/html/qemu-devel/2020-10/msg06560.html
> 
> Jiahui Cen (9):
>   qapi/block-core: Add retry option for error action
>   block-backend: Introduce retry timer
>   block-backend: Add device specific retry callback
>   block-backend: Enable retry action on errors
>   block-backend: Add timeout support for retry
>   block: Add error retry param setting
>   virtio_blk: Add support for retry on errors
>   scsi-bus: Refactor the code that retries requests
>   scsi-disk: Add support for retry on errors
> 
>  block/block-backend.c          | 68 ++++++++++++++++++++
>  blockdev.c                     | 52 +++++++++++++++
>  hw/block/block.c               | 10 +++
>  hw/block/virtio-blk.c          | 21 +++++-
>  hw/scsi/scsi-bus.c             | 16 +++--
>  hw/scsi/scsi-disk.c            | 16 +++++
>  include/hw/block/block.h       |  7 +-
>  include/hw/scsi/scsi.h         |  1 +
>  include/sysemu/block-backend.h | 10 +++
>  qapi/block-core.json           |  9 ++-
>  10 files changed, 199 insertions(+), 11 deletions(-)
>