On Thu, Oct 27, 2016 at 11:59:43PM -0700, Christoph Hellwig wrote:
> > +	mm_segment_t currentfs = get_fs();
> >
> >  	if (!ib_dev)
> >  		return -EIO;
> > @@ -240,8 +242,10 @@ static long ib_uverbs_cmd_verbs(struct ib_device *ib_dev,
> >  		goto out;
> >  	}
> >
> > +	set_fs(oldfs);
> >  	err = uverbs_handle_action(buf, ctx->uattrs, hdr->num_attrs, ib_dev,
> >  				   file, action, ctx->uverbs_attr_array);
> > +	set_fs(currentfs);
>
> Adding this magic in new code is not acceptable.  Any given API
> must take either a kernel or a user pointer.

And it is indeed happen for new code. This magic is needed to allow legacy
write interface to be converted to new ioctl interface internally in
kernel.


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