Re: dm: change dm_get_target_type() to check for module load error

[Shuah Khan]

On 10/6/21 2:35 PM, Mike Snitzer wrote:
> On Mon, Oct 04 2021 at  4:06P -0400,
> Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > dm_get_target_type() doesn't check error return from request_module().
> > Change to check for error and return NULL instead of trying to get
> > target type again which would fail.
> >
> > Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/md/dm-target.c | 11 ++++++++---
> >   1 file changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
> > index 64dd0b34fcf4..0789e9f91d3a 100644
> > --- a/drivers/md/dm-target.c
> > +++ b/drivers/md/dm-target.c
> > @@ -41,17 +41,22 @@ static struct target_type *get_target_type(const char *name)
> >   	return tt;
> >   }
> >   
> > -static void load_module(const char *name)
> > +static int load_module(const char *name)
> >   {
> > -	request_module("dm-%s", name);
> > +	return request_module("dm-%s", name);
> >   }
> >   
> >   struct target_type *dm_get_target_type(const char *name)
> >   {
> >   	struct target_type *tt = get_target_type(name);
> > +	int ret;
> >   
> >   	if (!tt) {
> > -		load_module(name);
> > +		ret = load_module(name);
> > +		if (ret < 0) {
> > +			pr_err("Module %s load failed %d\n", name, ret);
> > +			return NULL;
> > +		}
> >   		tt = get_target_type(name);
> >   	}
> >   
> > --
> > 2.30.2
>
> While I appreciate your intent, the reality is that multiple targets
> may be made available in a given module.  And so loading one dm module
> may bring in access to N targets.  There isn't a rigid 1:1 mapping of
> target modules to names.  And there may not even be a loadable module
> that has the name dm-${name} -- but that doesn't mean the target_type
> won;t have been loaded into DM for it to access.

Thanks for the explanation.

-- Shuah