On Mon, Sep 07, 2026 at 01:07:42PM +0200, Niklas Cassel wrote: > Zone write pointers are tracked and reported in units of > BDRV_SECTOR_SIZE, so an append whose data size is not a multiple of it > would leave a write pointer that cannot be represented, neither in a > BlockZoneDescriptor nor in the virtio and NVMe zone reports derived from > one. > > Nothing states that invariant. file-posix, the only driver that carries > out an append itself, does enforce it, but only as a side effect of > checking each iovec against BlockLimits.write_granularity, which is never > smaller than the sector size. That conflates two constraints: the sector > granularity holds for every driver, whereas write_granularity describes a > coarser requirement of the medium below a driver, and only a driver that > has such a medium should express it. > > Check the invariant once in bdrv_co_zone_append(), so that it no longer > rests on a driver that happens to have a granularity of its own to > report. > > This is a lower bound, not the alignment that a guest has to observe. The > block layer cannot know that one, because it also depends on the logical > block size the device is configured with, which is a property of the > frontend. The alignment that applies to a guest is the larger of the two, > and it is the frontend that reports it, that validates requests against > it, and that has to refuse a device whose write pointers do not satisfy > it. > > Reviewed-by: Damien Le Moal <[email protected]> > Signed-off-by: Niklas Cassel <[email protected]> > --- > block/io.c | 10 ++++++++++ > 1 file changed, 10 insertions(+)
Reviewed-by: Stefan Hajnoczi <[email protected]>
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