Re: [PATCH 2/2] scsi: enforce unlimited max_segment_size when virt_boundary_mask is set

[Ming Lei <ming.lei@redhat.com>]

On Mon, Jun 23, 2025 at 10:02:54AM +0200, Christoph Hellwig wrote:
> The virt_boundary_mask limit requires an unlimited max_segment_size for
> bio splitting to not corrupt data.  Historically, the block layer tried
> to validate this, although the check was half-hearted until the addition
> of the atomic queue limits API.  The full blown check than triggered
> issues with stacked devices incorrectly inheriting limits such as the
> virt boundary and got disabled in commit b561ea56a264 ("block: allow
> device to have both virt_boundary_mask and max segment size") instead of
> fixing the issue properly.
> 
> Ensure that the SCSI mid layer doesn't set the default low
> max_segment_size limit for this case, and check for invalid
> max_segment_size values in the host template, similar to the original
> block layer check given that SCSI devices can't be stacked.
> 
> This fixes reported data corruption on storvsc, although as far as I can
> tell storvsc always failed to properly set the max_segment_size limit as
> the SCSI APIs historically applied that when setting up the host, while
> storvsc only set the virt_boundary_mask when configuring the scsi_device.
> 
> Fixes: 81988a0e6b03 ("storvsc: get rid of bounce buffer")
> Fixes: b561ea56a264 ("block: allow device to have both virt_boundary_mask and max segment size")
> Reported-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming