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@dwi...
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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.
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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(-)