Re: [PATCH 2/2] nbd: add netlink reconfigure resize support v3

[Josef Bacik <josef@toxicpanda.com>]

On Wed, May 29, 2019 at 03:16:06PM -0500, Mike Christie wrote:
> If the device is setup with ioctl we can resize the device after the
> initial setup, but if the device is setup with netlink we cannot use the
> resize related ioctls and there is no netlink reconfigure size ATTR
> handling code.
> 
> This patch adds netlink reconfigure resize support to match the ioctl
> interface.
> 
> Signed-off-by: Mike Christie <mchristi@redhat.com>

Sorry I missed this too, but I think there's a problem with this actually.

> ---
> 
> V3;
> - If the device size or block size has not changed do not call
> nbd_size_set.
> 
> V2:
> - Merge reconfig and connect resize related code to helper and avoid
> multiple nbd_size_set calls.
> 
>  drivers/block/nbd.c | 48 ++++++++++++++++++++++++++++++---------------
>  1 file changed, 32 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 236253fbf455..9486555e6391 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1685,6 +1685,30 @@ nbd_device_policy[NBD_DEVICE_ATTR_MAX + 1] = {
>  	[NBD_DEVICE_CONNECTED]		=	{ .type = NLA_U8 },
>  };
>  
> +static int nbd_genl_size_set(struct genl_info *info, struct nbd_device *nbd)
> +{
> +	struct nbd_config *config = nbd->config;
> +	u64 bsize = config->blksize;
> +	u64 bytes = config->bytesize;
> +
> +	if (info->attrs[NBD_ATTR_SIZE_BYTES])
> +		bytes = nla_get_u64(info->attrs[NBD_ATTR_SIZE_BYTES]);
> +
> +	if (info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]) {
> +		bsize = nla_get_u64(info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]);
> +		if (!bsize)
> +			bsize = NBD_DEF_BLKSIZE;
> +		if (!nbd_is_valid_blksize(bsize)) {
> +			printk(KERN_ERR "Invalid block size %llu\n", bsize);
> +			return -EINVAL;
> +		}
> +	}
> +
> +	if (bytes != config->bytesize || bsize != config->blksize)
> +		nbd_size_set(nbd, bsize, div64_u64(bytes, bsize));

This part won't actually update the bdev if there already is one because
nbd->task_recv is NULL for netlink related devices.  Probably need to fix that
to update the bdev unconditionally, and then just see if bdget_disk() returns
NULL in nbd_size_update.  Also I hate myself for how many size update functions
there are.  Thanks,

Josef