Re: [PATCH] nvme-multipath: set BIO_REMAPPED on bios remapped to per-path namespace disks

[Keith Busch <kbusch@kernel.org>]

On Tue, May 19, 2026 at 08:53:03AM +0200, hch@lst.de wrote:
> On Mon, May 18, 2026 at 01:23:17PM -0600, Keith Busch wrote:
> > 
> > Any reason nvme multipath can't call submit_bio_noacct_nocheck()
> > directly instead? If it's safe to skip the eod check here, then it
> > looks safe to skip everything else too.
> 
> We really shouldn't expose that, and it doesn't quite to the
> right checks here.
> 
> But I think the proper fix is to stop using bio_set_dev entirely.
> We do not want to associate the bio with a new blkg as those are
> basically not going to exist for the underlying devices.  I'm also
> not sure we want to allow another round of BPF throttling either.

Simply dropping the bio_set_dev usage doesn't really fix the problem
here. Sure, bio_set_dev clears the BIO_REMAPPED flag, but it's not
guaranteed that flag was set in the first place.

I have an alternate proposal that's part of a larger series. This can
notify the driver of an early error so it can decide how to deal with
the bio:

  https://lore.kernel.org/linux-block/20260519172326.3462354-6-kbusch@meta.com/