Re: [PATCH v2 17/22] drivers/base: Make device_find_child_by_name() compatible with sysfs inputs

[Greg Kroah-Hartman]

On Mon, Jul 13, 2020 at 08:39:43AM -0700, Dan Williams wrote:
> On Sun, Jul 12, 2020 at 10:09 AM Greg Kroah-Hartman
> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Sun, Jul 12, 2020 at 09:27:37AM -0700, Dan Williams wrote:
> > > Use sysfs_streq() in device_find_child_by_name() to allow it to use a
> > > sysfs input string that might contain a trailing newline.
> > >
> > > The other "device by name" interfaces,
> > > {bus,driver,class}_find_device_by_name(), already account for sysfs
> > > strings.
> > >
> > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > > Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> > > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> > > ---
> > >  drivers/base/core.c |    2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > > index 67d39a90b45c..5d31b962c898 100644
> > > --- a/drivers/base/core.c
> > > +++ b/drivers/base/core.c
> > > @@ -3078,7 +3078,7 @@ struct device *device_find_child_by_name(struct device *parent,
> > >
> > >       klist_iter_init(&parent->p->klist_children, &i);
> > >       while ((child = next_device(&i)))
> > > -             if (!strcmp(dev_name(child), name) && get_device(child))
> > > +             if (sysfs_streq(dev_name(child), name) && get_device(child))
> >
> > Who wants to call this function with a name passed from userspace?
> >
> > Not objecting to it, just curious...
> >
> 
> The series that incorporates this patch adds a partitioning mechanism
> to "device-dax region" devices with an:
>     "echo 1 > regionX/create" to create a new partition / sub-instance
> of a region, and...
>     "echo $devname > regionX/delete" to delete. Where $devname is
> searched in the child devices of regionX to trigger device_del().

Shouldn't that be done in configfs, not sysfs?

> This arrangement avoids one of the design mistakes of libnvdimm which
> uses a sysfs attribute of the device to delete itself. Parent-device
> triggered deletion rather than self-deletion avoids those locking
> entanglements.

Ugh, yeah, getting rid of that would be great, it's a mess.  I think
scsi still does that :(

thanks,

greg k-h