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Subject[PATCH v3 0/6] mm: Fix pfn_to_online_page() with respect to ZONE_DEVICE
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Changes since v2 [1]:
- Collect some reviewed-by's from David and Oscar

- Rework subsection validity to include pfn_valid() gated by
CONFIG_HAVE_ARCH_PFN_VALID (David, Oscar)

- Introduce pgmap_pfn_valid() to validate metadata vs data in a pgmap (David)

! Kill put_ref_page(): the extra "if (ref_page) put_page(ref_page)" still
feels more cluttered than adding a tiny helper. (Oscar)

[1]: http://lore.kernel.org/r/161044407603.1482714.16630477578392768273.stgit@dwillia2-desk3.amr.corp.intel.com

---

Michal reminds that the discussion about how to ensure pfn-walkers do
not get confused by ZONE_DEVICE pages never resolved. A pfn-walker that
uses pfn_to_online_page() may inadvertently translate a pfn as online
and in the page allocator, when it is offline managed by a ZONE_DEVICE
mapping (details in Patch 3: ("mm: Teach pfn_to_online_page() about
ZONE_DEVICE section collisions")).

The 2 proposals under consideration are teach pfn_to_online_page() to be
precise in the presence of mixed-zone sections, or teach the memory-add
code to drop the System RAM associated with ZONE_DEVICE collisions. In
order to not regress memory capacity by a few 10s to 100s of MiB the
approach taken in this set is to add precision to pfn_to_online_page().

In the course of validating pfn_to_online_page() a couple other fixes
fell out:

1/ soft_offline_page() fails to drop the reference taken in the
madvise(..., MADV_SOFT_OFFLINE) case.

2/ The libnvdimm sysfs attribute visibility code was failing to publish
the resource base for memmap=ss!nn defined namespaces. This is needed
for the regression test for soft_offline_page().

3/ memory_failure() uses get_dev_pagemap() to lookup ZONE_DEVICE pages,
however that mapping may contain data pages and metadata raw pfns.
Introduce pgmap_pfn_valid() to delineate the 2 types and fail the
handling of raw metadata pfns.

---

Dan Williams (6):
mm: Move pfn_to_online_page() out of line
mm: Teach pfn_to_online_page() to consider subsection validity
mm: Teach pfn_to_online_page() about ZONE_DEVICE section collisions
mm: Fix page reference leak in soft_offline_page()
mm: Fix memory_failure() handling of dax-namespace metadata
libnvdimm/namespace: Fix visibility of namespace resource attribute


drivers/nvdimm/namespace_devs.c | 10 +++---
include/linux/memory_hotplug.h | 17 +--------
include/linux/memremap.h | 6 +++
include/linux/mmzone.h | 22 ++++++++----
mm/memory-failure.c | 26 ++++++++++++--
mm/memory_hotplug.c | 70 +++++++++++++++++++++++++++++++++++++++
mm/memremap.c | 15 ++++++++
7 files changed, 134 insertions(+), 32 deletions(-)

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