Linux Virtualization - Dec 2019 - [PATCH 15/24] compat_ioctl: scsi: move ioctl handling into drivers

On Wed, Dec 11, 2019 at 09:42:49PM +0100, Arnd Bergmann
wrote:
> Each driver calling scsi_ioctl() gets an equivalent compat_ioctl()
> handler that implements the same commands by calling scsi_compat_ioctl().
> 
> The scsi_cmd_ioctl() and scsi_cmd_blk_ioctl() functions are compatible
> at this point, so any driver that calls those can do so for both native
> and compat mode, with the argument passed through compat_ptr().
> 
> With this, we can remove the entries from fs/compat_ioctl.c.  The new
> code is larger, but should be easier to maintain and keep updated with
> newly added commands.
> 
> Signed-off-by: Arnd Bergmann <arnd at arndb.de>
> ---
>  drivers/block/virtio_blk.c |   3 +
>  drivers/scsi/ch.c          |   9 ++-
>  drivers/scsi/sd.c          |  50 ++++++--------
>  drivers/scsi/sg.c          |  44 ++++++++-----
>  drivers/scsi/sr.c          |  57 ++++++++++++++--
>  drivers/scsi/st.c          |  51 ++++++++------
>  fs/compat_ioctl.c          | 132 +------------------------------------
>  7 files changed, 142 insertions(+), 204 deletions(-)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 7ffd719d89de..fbbf18ac1d5d 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -405,6 +405,9 @@ static int virtblk_getgeo(struct block_device *bd,
struct hd_geometry *geo)
>  
>  static const struct block_device_operations virtblk_fops = {
>  	.ioctl  = virtblk_ioctl,
> +#ifdef CONFIG_COMPAT
> +	.compat_ioctl = blkdev_compat_ptr_ioctl,
> +#endif
>  	.owner  = THIS_MODULE,
>  	.getgeo = virtblk_getgeo,
>  };
Hmm - is virtio blk lumped in with scsi things intentionally?

-- 
MST

On 12/12/19 00:05, Michael S. Tsirkin wrote:
>> @@ -405,6 +405,9 @@ static int virtblk_getgeo(struct block_device *bd,
struct hd_geometry *geo)
>>  
>>  static const struct block_device_operations virtblk_fops = {
>>  	.ioctl  = virtblk_ioctl,
>> +#ifdef CONFIG_COMPAT
>> +	.compat_ioctl = blkdev_compat_ptr_ioctl,
>> +#endif
>>  	.owner  = THIS_MODULE,
>>  	.getgeo = virtblk_getgeo,
>>  };
> Hmm - is virtio blk lumped in with scsi things intentionally?
I think it's because the only ioctl for virtio-blk is SG_IO.  It makes
sense to lump it in with scsi, but I wouldn't mind getting rid of
CONFIG_VIRTIO_BLK_SCSI altogether.

Paolo

On Thu, Dec 12, 2019 at 1:28 AM Paolo Bonzini <pbonzini at redhat.com>
wrote:
> On 12/12/19 00:05, Michael S. Tsirkin wrote:
> >> @@ -405,6 +405,9 @@ static int virtblk_getgeo(struct block_device
*bd, struct hd_geometry *geo)
> >>
> >>  static const struct block_device_operations virtblk_fops = {
> >>      .ioctl  = virtblk_ioctl,
> >> +#ifdef CONFIG_COMPAT
> >> +    .compat_ioctl = blkdev_compat_ptr_ioctl,
> >> +#endif
> >>      .owner  = THIS_MODULE,
> >>      .getgeo = virtblk_getgeo,
> >>  };
> > Hmm - is virtio blk lumped in with scsi things intentionally?
>
> I think it's because the only ioctl for virtio-blk is SG_IO.  It makes
> sense to lump it in with scsi, but I wouldn't mind getting rid of
> CONFIG_VIRTIO_BLK_SCSI altogether.
It currently calls scsi_cmd_blk_ioctl(), which implements a bunch of ioctl
commands, including some that are unrelated to SG_IO:

                case SG_GET_VERSION_NUM:
                case SCSI_IOCTL_GET_IDLUN:
                case SCSI_IOCTL_GET_BUS_NUMBER:
                case SG_SET_TIMEOUT:
                case SG_GET_TIMEOUT:
                case SG_GET_RESERVED_SIZE:
                case SG_SET_RESERVED_SIZE:
                case SG_EMULATED_HOST:
                case SG_IO: {
                case CDROM_SEND_PACKET:
                case SCSI_IOCTL_SEND_COMMAND:
                case CDROMCLOSETRAY:
                case CDROMEJECT:

My patch changes all callers of this function, and the idea is
to preserve the existing behavior through my series, so I think
it makes sense to keep my patch as is.

I would assume that calling scsi_cmd_blk_ioctl() is harmless
here, but if you want to remove it or limit the set of supported
commands, that should be independent of my change.

       Arnd

On Thu, Dec 12, 2019 at 01:28:08AM +0100, Paolo Bonzini
wrote:
> On 12/12/19 00:05, Michael S. Tsirkin wrote:
> >> @@ -405,6 +405,9 @@ static int virtblk_getgeo(struct block_device
*bd, struct hd_geometry *geo)
> >>  
> >>  static const struct block_device_operations virtblk_fops = {
> >>  	.ioctl  = virtblk_ioctl,
> >> +#ifdef CONFIG_COMPAT
> >> +	.compat_ioctl = blkdev_compat_ptr_ioctl,
> >> +#endif
> >>  	.owner  = THIS_MODULE,
> >>  	.getgeo = virtblk_getgeo,
> >>  };
> > Hmm - is virtio blk lumped in with scsi things intentionally?
> 
> I think it's because the only ioctl for virtio-blk is SG_IO.
Oh right, I forgot about that one ...
>  It makes
> sense to lump it in with scsi, but I wouldn't mind getting rid of
> CONFIG_VIRTIO_BLK_SCSI altogether.
> 
> Paolo

On Thu, Dec 12, 2019 at 01:28:08AM +0100, Paolo Bonzini
wrote:
> I think it's because the only ioctl for virtio-blk is SG_IO.  It makes
> sense to lump it in with scsi, but I wouldn't mind getting rid of
> CONFIG_VIRTIO_BLK_SCSI altogether.
CONFIG_VIRTIO_BLK_SCSI has been broken for about two years, as it
never set the QUEUE_FLAG_SCSI_PASSTHROUGH flag after that was
introduced.  I actually have a patch that I plan to send to remove
this support as it was a really idea to start with (speaking as
the person who had that idea back in the day).