Re: [PATCH v6 1/4] sg: use rwsem to solve race during exclusive open

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Wed, 2013-08-28 at 18:07 +0800, Vaughan Cao wrote:
> @@ -331,17 +330,20 @@ sg_open(struct inode *inode, struct file *filp)
>         }
>         if ((sfp = sg_add_sfp(sdp, dev)))
>                 filp->private_data = sfp;
> -       else {
> +               /* retval is already provably zero at this point
> because of the
> +                * check after retval =
> scsi_autopm_get_device(sdp->device))
> +                */
> +       else
> +               retval = -ENOMEM;
> +
> +       if (retval) {
> +sem_out:

There's still no need for the double if.  You know the value of retval
in each of the legs of the first if; its only non zero for the else leg,
so you can combine them thus:

        if ((sfp = sg_add_sfp(sdp, dev)))
                filp->private_data = sfp;
               /* retval is already provably zero at this point because of the
                * check after retval scsi_autopm_get_device(sdp->device))
                */
       else {
               retval = -ENOMEM;
 sem_out:
...

James