Re: [PATCH v10 00/13] mm: Sub-section memory hotplug support

Oscar Salvador
2019-06-20T17:00:44Z

On Tue, Jun 18, 2019 at 10:51:33PM -0700, Dan Williams wrote:
> Changes since v9 [1]:
> - Fix multiple issues related to the fact that pfn_valid() has
> traditionally returned true for any pfn in an 'early' (onlined at
> boot) section regardless of whether that pfn represented 'System RAM'.
> Teach pfn_valid() to maintain its traditional behavior in the presence
> of subsections. Specifically, subsection precision for pfn_valid() is
> only considered for non-early / hot-plugged sections. (Qian)
>
> - Related to the first item introduce a SECTION_IS_EARLY
> (->section_mem_map flag) to remove the existing hacks for determining
> an early section by looking at whether the usemap was allocated from the
> slab.
>
> - Kill off the EEXIST hackery in __add_pages(). It breaks
> (arch_add_memory() false-positive) the detection of subsection
> collisions reported by section_activate(). It is also obviated by
> David's recent reworks to move the 'System RAM' request_region() earlier
> in the add_memory() sequence().
>
> - Switch to an arch-independent / static subsection-size of 2MB.
> Otherwise, a per-arch subsection-size is a roadblock on the path to
> persistent memory namespace compatibility across archs. (Jeff)
>
> - Update the changelog for "libnvdimm/pfn: Fix fsdax-mode namespace
> info-block zero-fields" to clarify that the "Cc: stable" is only there
> as safety measure for a distro that decides to backport "libnvdimm/pfn:
> Stop padding pmem namespaces to section alignment", otherwise there is
> no known bug exposure in older kernels. (Andrew)
>
> - Drop some redundant subsection checks (Oscar)
>
> - Collect some reviewed-bys
>
> [1]: https://lore.kernel.org/lkml/155977186863.2443951.9036044808311959913.stgit@dwillia2-desk3.amr.corp.intel.com/

Hi Dan,

I am planning to give it a final review later tomorrow.
Now that this work is settled, I took the chance to dust off and push my
vmemmap-hotplug, and I am working on that right now.
But I would definetely come back to this tomorrow.

Thanks for the work

--
Oscar Salvador
SUSE L3