On Fri, Jun 10, 2022 at 11:11:00AM -0400, Mike Snitzer wrote:
> On Fri, Jun 10 2022 at 1:15P -0400,
> Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > On Fri, Jun 10, 2022 at 04:22:00AM +0000, Oleksandr Tymoshenko wrote:
> > > I believe this commit introduced a regression in dm verity on systems
> > > where data device is an NVME one. Loading table fails with the
> > > following diagnostics:
> > >
> > > device-mapper: table: table load rejected: including non-request-stackable devices
> > >
> > > The same kernel works with the same data drive on the SCSI interface.
> > > NVME-backed dm verity works with just this commit reverted.
> > >
> > > I believe the presence of the immutable partition is used as an indicator
> > > of special case NVME configuration and if the data device's name starts
> > > with "nvme" the code tries to switch the target type to
> > > DM_TYPE_NVME_BIO_BASED (drivers/md/dm-table.c lines 1003-1010).
> > >
> > > The special NVME optimization case was removed in
> > > 5.10 by commit 9c37de297f6590937f95a28bec1b7ac68a38618f, so only 5.4 is
> > > affected.
> > >
> >
> > Why wouldn't 4.9, 4.14, and 4.19 also be affected here? Should I also
> > just queue up 9c37de297f65 ("dm: remove special-casing of bio-based
> > immutable singleton target on NVMe") to those older kernels? If so,
> > have you tested this and verified that it worked?
>
> Sorry for the unforeseen stable@ troubles here!
>
> In general we'd be fine to apply commit 9c37de297f65 but to do it
> properly would require also making sure commits that remove
> "DM_TYPE_NVME_BIO_BASED", like 8d47e65948dd ("dm mpath: remove
> unnecessary NVMe branching in favor of scsi_dh checks") are applied --
> basically any lingering references to DM_TYPE_NVME_BIO_BASED need to
> be removed.
>
> The commit header for 8d47e65948dd documents what
> DM_TYPE_NVME_BIO_BASED was used for.. it was dm-mpath specific and
> "nvme" mode really never got used by any userspace that I'm aware of.
>
> Sadly I currently don't have the time to do this backport for all N
> stable kernels... :(
>
> But if that backport gets out of control: A simpler, albeit stable@
> unicorn, way to resolve this is to simply revert 9c37de297f65 and make
> it so that DM-mpath and DM core just used bio-based if "nvme" is
> requested by dm-mpath, so also in drivers/md/dm-mpath.c e.g.:
>
> @@ -1091,8 +1088,6 @@ static int parse_features(struct dm_arg_set *as, struct multipath *m)
>
> if (!strcasecmp(queue_mode_name, "bio"))
> m->queue_mode = DM_TYPE_BIO_BASED;
> else if (!strcasecmp(queue_mode_name, "nvme"))
> - m->queue_mode = DM_TYPE_NVME_BIO_BASED;
> + m->queue_mode = DM_TYPE_BIO_BASED;
> else if (!strcasecmp(queue_mode_name, "rq"))
> m->queue_mode = DM_TYPE_REQUEST_BASED;
> else if (!strcasecmp(queue_mode_name, "mq"))
>
> Mike
>
Ok, please submit a working patch for the kernels that need it so that
we can review and apply it to solve this regression.
thanks,
greg k-h
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