Re: [PATCH v14 3/6] qcow2: add configurations for zoned format extension

On Fri, Aug 07, 2026 at 02:06:52AM +0200, Niklas Cassel wrote:
> On Fri, Aug 07, 2026 at 01:56:36AM +0200, Niklas Cassel wrote:
> > Looking at the write_granularity in virtio-blk + file-posix:
> > for blkcfg.zoned.write_granularity, which is what virtio-blk exposes to
> > the guest, it is initialized using:
> > https://github.com/qemu/qemu/blob/v11.1.0-rc3/hw/block/virtio-blk.c#L1257
> > conf->logical_block_size:
> > https://github.com/qemu/qemu/blob/v11.1.0-rc3/hw/block/virtio-blk.c#L1183
> > 
> > and the value we set to the qemu block layer - bs->bl.write_granularity,
> > which file-posix initilizes using:
> > https://github.com/qemu/qemu/blob/v11.1.0-rc3/block/file-posix.c#L1498-L1501
> > the sysfs value for physical_block_size.
> 
> If we are using sysfs, I wonder why this code does not simply read:
> /sys/block/<disk>/queue/zone_write_granularity
> instead.
> 
> 
> But that would still be inconsistent with blkcfg.zoned.write_granularity which
> is initialized using conf->logical_block_size.

At least QEMU is currently bug compatible with Linux:

linux $ git grep "zone_write_granularity ="
block/blk-settings.c:           lim->zone_write_granularity = lim->logical_block_size;
drivers/scsi/sd_zbc.c:  lim->zone_write_granularity = sdkp->physical_block_size;

Where blk-settings is using the logical block size, but SCSI is using the
physical block size :)


Kind regards,
Niklas