Re: [PATCH RFC 3/4] dm-stripe: limit chunk_sectors to the stripe size

[John Garry]

On 06/06/2025 16:16, Nilay Shroff wrote:
> > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> > index 24a857ff6d0b..4f1f7173740c 100644
> > --- a/drivers/md/dm-table.c
> > +++ b/drivers/md/dm-table.c
> > @@ -430,6 +430,10 @@ static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
> >   		return 0;
> >   	}
> >   
> > +	/* For striped types, limit the chunk_sectors to the chunk size */
> > +	if (dm_target_supports_striped(ti->type))
> > +		limits->chunk_sectors = len >> SECTOR_SHIFT;
> > +
> I think here "len" refers to the total size of dm target and not the
> chunk sectors. So we need to modify this and take into account chunk sectors..
> We can get chunk sectors, for example, like this:
>
> 	struct stripe_c *sc = ti->private;
> 	limits->chunk_sectors = sc->chunk_size;

right

I find that the terminology used in the dm code for stripe width and 
size a bit confusing.

> But again struct stripe_c is private to dm-stripe.c and so we can't access it
> here directly in dm-table.c Better we add a new callback function for dm target
> type under struct target_type and then use that callback to get chunk sector.
>
> struct target_type stripe_target = {
>          ...
>          .chunk_sectors = stripe_chunk_sectors,
>          ...
> }


Please see reply to Mikulas on this same topic.

Thanks,
John