Re: [PATCH 2/2] dm-raid1: don't fail the mirror for invalid I/O errors

[Benjamin Marzinski <bmarzins@redhat.com>]

On Tue, Jul 07, 2026 at 03:44:54PM -0400, Mike Snitzer wrote:
> On Mon, Jul 06, 2026 at 02:52:33PM -0600, Keith Busch wrote:
> > On Wed, Jun 24, 2026 at 01:14:03PM +0200, Mikulas Patocka wrote:
> > > This approach is OK, I will stage the patches when 7.2-rc1 comes out and 
> > > when I'll fork the dm git branches.
> > > 
> > > I suggest one change - it is kind of hacky when multiple I/O completion 
> > > callbacks write into io->orig_bio->bi_status concurrently - so it would be 
> > > better to not do it and maintain and return separate bit mask for 
> > > non-retryable errors.
> > > 
> > > For example:
> > > 
> > > static void complete_io(struct io *io)
> > > {
> > >         unsigned long error_bits = io->error_bits;
> > >         unsigned long nonretryable_error_bits = io->nonretryable_error_bits;
> > >         io_notify_fn fn = io->callback;
> > >         void *context = io->context;
> > > 
> > >         if (io->vma_invalidate_size)
> > >                 invalidate_kernel_vmap_range(io->vma_invalidate_address,
> > >                                              io->vma_invalidate_size);
> > > 
> > >         mempool_free(io, &io->client->pool);
> > >         fn(error_bits, nonretryable_error_bits, context);
> > > }
> > > 
> > > static void dec_count(struct io *io, unsigned int region, blk_status_t error)
> > > {
> > >         if (unlikely(error == BLK_STS_NOTSUPP) || unlikely(error == BLK_STS_INVAL))
> > > 		set_bit(region, &io->nonretryable_error_bits);
> > >         else if (unlikely(error != BLK_STS_OK))
> > >                 set_bit(region, &io->error_bits);
> > > 
> > >         if (atomic_dec_and_test(&io->count))
> > >                 complete_io(io);
> > > }
> > > 
> > > Please send the updated patch that uses this approach.
> > 
> > Sure thing, I can get started on that. Though I think it's largely
> > obviated if we get the block layer to handle things early rather than
> > submit malformed bio's, and this will accomplish that:
> > 
> >   https://lore.kernel.org/dm-devel/20260624170905.3972095-1-kbusch@meta.com/
> 
> Jens hasn't picked that series up yet. Jens?
> 
> > But I can certainly respin this series as it provides a more indepth
> > defence.
> > 
> > I also owe an update on the relaxed dm-crypt direct-io memory alignment
> > as well, as that series fell through the cracks on me for the previous
> > merge window.
> 
> So where does dm-raid1 and dm-crypt stand relative to these DIO memory
> alignment changes?  Inferring they are pretty exposed.
> 
> > > BTW. I think that blk_path_error should also test for BLK_STS_INVAL and 
> > > return false, otherwise, dm-multipath would be suffering from this bug 
> > > too. Ben, could you test it?
> > 
> > Good point.
> 
> Would appreciate knowing if multipath exposed too.

I can't make it happen. I can reproduce this using dm-mirror, but when I
try with dm-multipath, it fails with BLK_STS_INVAL before it ever makes
it into the request layer.

blk_mq_submit_bio() -> __bio_split_to_limits() -> bio_split_rw() ->
bio_split_rw_at() -> bio_split_io_at()

bio_split_io_at() checks the bio_vec alignment and fails with -EINVAL,
causing the bio to get failed.

-Ben

> 
> Thanks,
> Mike