Re: [PATCH] scsi_lib: Align max_sectors to kb

Christoph Hellwig
2024-04-19T06:20:45Z

On Thu, Apr 18, 2024 at 06:46:06PM +0200, Martin Wilck wrote:
> > Why would we?  It makes absolutly no sense to inherit these limits,
> > the lower device will split anyway which is very much the point of
> > the immutable bio_vec work.
> >
>
> Sorry, I don't follow. With (request-based) dm-multipath on top of
> SCSI, we hit the "over max size limit" condition in
> blk_insert_cloned_request() [1], which will cause IO to fail at the dm
> level. So at least in this configuration, it's crucial that the upper
> device inherit the lower device's limits.

Oh, indeed. Request based multipath is different from everyone else.
I really wish we could spend the effort to convert it to bio based
and remove this special case..