On Mon, Apr 05, 2021 at 07:15:32PM -0300, Jason Gunthorpe wrote:
> On Mon, Apr 05, 2021 at 04:09:39PM +0300, Gal Pressman wrote:
> > On 05/04/2021 15:39, Leon Romanovsky wrote:
> > > On Mon, Apr 05, 2021 at 03:15:18PM +0300, Gal Pressman wrote:
> > >> On 05/04/2021 14:57, Leon Romanovsky wrote:
> > >>> On Mon, Apr 05, 2021 at 02:47:21PM +0300, Gal Pressman wrote:
> > >>>> The new attribute indicates that the kernel copies DMA pages on fork,
> > >>>> hence libibverbs' fork support through madvise and MADV_DONTFORK is not
> > >>>> needed.
> > >>>>
> > >>>> The introduced attribute is always reported as supported since the
> > >>>> kernel has the patch that added the copy-on-fork behavior. This allows
> > >>>> the userspace library to identify older vs newer kernel versions.
> > >>>> Extra care should be taken when backporting this patch as it relies on
> > >>>> the fact that the copy-on-fork patch is merged, hence no check for
> > >>>> support is added.
> > >>>
> > >>> Please be more specific, add SHA-1 of that patch and wrote the same
> > >>> comment near "err = nla_put_u8(msg, RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK,
> > >>> 1);" line.
> > >>>
> > >>> Thanks
> > >>
> > >> Should I put the original commit here? There were quite a lot of bug fixes and
> > >> followups that are required.
> > >
> > > IMHO, the last commit SHA will be enough, the one that has working
> > > functionality from your POV.
> >
> > OK, so that would be:
> > 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm")
>
> No, lets put them all
The more data the better chance that it will be missed.
It is much saner to add last commit.
>
> And I'd mark them with a Fixes: and a huge comment saying not to
> backport this and that the Fixes lines exist to *prevent* tooling from
> wrongly backporting to kernels that cannot support this.
>
> And email Sasha to see if there is a magic text we can add to prevent
> auto backporting
Don't add Fixes, maybe?
>
> > Which I now realize for-next isn't rebased on top of it yet, so these patches
> > should be applied after rebasing to v5.12-rc5.
>
> I will sort it out
>
> Jason
