Re: [PATCH v4 4/7] file-posix: try BLKSECTGET on block devices too, do not round to power of 2

[Eric Blake]

On Tue, Jun 08, 2021 at 03:16:31PM +0200, Paolo Bonzini wrote:
> bs->sg is only true for character devices, but block devices can also
> be used with scsi-block and scsi-generic.  Unfortunately BLKSECTGET
> returns bytes in an int for /dev/sgN devices, and sectors in a short
> for block devices, so account for that in the code.

Gotta love inconsistent and poorly-documented kernel interfaces! (on my
system, 'man -k BLKSECTGET' had no hits)

> 
> The maximum transfer also need not be a power of 2 (for example I have
> seen disks with 1280 KiB maximum transfer) so there's no need to pass
> the result through pow2floor.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  block/file-posix.c | 44 ++++++++++++++++++++++++--------------------
>  1 file changed, 24 insertions(+), 20 deletions(-)
>

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org