Stefan Hajnoczi <stefa...@gmail.com> 于2023年2月6日周一 20:16写道： > > On Sun, 29 Jan 2023 at 05:31, Sam Li <faithilike...@gmail.com> wrote: > > > > Add the documentation about the zoned device support to virtio-blk > > emulation. > > > > Signed-off-by: Sam Li <faithilike...@gmail.com> > > Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com> > > Reviewed-by: Damien Le Moal <damien.lem...@opensource.wdc.com> > > Reviewed-by: Dmitry Fomichev <dmitry.fomic...@wdc.com> > > --- > > docs/devel/zoned-storage.rst | 43 ++++++++++++++++++++++++++ > > docs/system/qemu-block-drivers.rst.inc | 6 ++++ > > 2 files changed, 49 insertions(+) > > create mode 100644 docs/devel/zoned-storage.rst > > This patch uses the old "zoned_host_device" BlockDriver name. Please > update it to "host_device". > > It's probably a good idea to search the patches for zoned_host_device > to find any other places that need to be updated. That can be done > with git log -p master.. | grep zoned_host_device.
Sorry for missing that. Will do. > > > diff --git a/docs/devel/zoned-storage.rst b/docs/devel/zoned-storage.rst > > new file mode 100644 > > index 0000000000..03e52efe2e > > --- /dev/null > > +++ b/docs/devel/zoned-storage.rst > > @@ -0,0 +1,43 @@ > > +============= > > +zoned-storage > > +============= > > + > > +Zoned Block Devices (ZBDs) divide the LBA space into block regions called > > zones > > +that are larger than the LBA size. They can only allow sequential writes, > > which > > +can reduce write amplification in SSDs, and potentially lead to higher > > +throughput and increased capacity. More details about ZBDs can be found at: > > + > > +https://zonedstorage.io/docs/introduction/zoned-storage > > + > > +1. Block layer APIs for zoned storage > > +------------------------------------- > > +QEMU block layer supports three zoned storage models: > > +- BLK_Z_HM: The host-managed zoned model only allows sequential writes > > access > > +to zones. It supports ZBD-specific I/O commands that can be used by a host > > to > > +manage the zones of a device. > > +- BLK_Z_HA: The host-aware zoned model allows random write operations in > > +zones, making it backward compatible with regular block devices. > > +- BLK_Z_NONE: The non-zoned model has no zones support. It includes both > > +regular and drive-managed ZBD devices. ZBD-specific I/O commands are not > > +supported. > > + > > +The block device information resides inside BlockDriverState. QEMU uses > > +BlockLimits struct(BlockDriverState::bl) that is continuously accessed by > > the > > +block layer while processing I/O requests. A BlockBackend has a root > > pointer to > > +a BlockDriverState graph(for example, raw format on top of file-posix). The > > +zoned storage information can be propagated from the leaf BlockDriverState > > all > > +the way up to the BlockBackend. If the zoned storage model in file-posix is > > +set to BLK_Z_HM, then block drivers will declare support for zoned host > > device. > > + > > +The block layer APIs support commands needed for zoned storage devices, > > +including report zones, four zone operations, and zone append. > > + > > +2. Emulating zoned storage controllers > > +-------------------------------------- > > +When the BlockBackend's BlockLimits model reports a zoned storage device, > > users > > +like the virtio-blk emulation or the qemu-io-cmds.c utility can use block > > layer > > +APIs for zoned storage emulation or testing. > > + > > +For example, to test zone_report on a null_blk device using qemu-io is: > > +$ path/to/qemu-io --image-opts -n > > driver=zoned_host_device,filename=/dev/nullb0 > > +-c "zrp offset nr_zones" > > diff --git a/docs/system/qemu-block-drivers.rst.inc > > b/docs/system/qemu-block-drivers.rst.inc > > index dfe5d2293d..0b97227fd9 100644 > > --- a/docs/system/qemu-block-drivers.rst.inc > > +++ b/docs/system/qemu-block-drivers.rst.inc > > @@ -430,6 +430,12 @@ Hard disks > > you may corrupt your host data (use the ``-snapshot`` command > > line option or modify the device permissions accordingly). > > > > +Zoned block devices > > + Zoned block devices can be passed through to the guest if the emulated > > storage > > + controller supports zoned storage. Use ``--blockdev zoned_host_device, > > + node-name=drive0,filename=/dev/nullb0`` to pass through ``/dev/nullb0`` > > + as ``drive0``. > > + > > Windows > > ^^^^^^^ > > > > -- > > 2.38.1 > > > >
