+ mm-teach-pfn_to_online_page-to-consider-subsection-validity.patch added to -mm tree

+ mm-teach-pfn_to_online_page-to-consider-subsection-validity.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm: teach pfn_to_online_page() to consider subsection validity
has been added to the -mm tree.  Its filename is
     mm-teach-pfn_to_online_page-to-consider-subsection-validity.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-teach-pfn_to_online_page-to-consider-subsection-validity.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-teach-pfn_to_online_page-to-consider-subsection-validity.patch

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Dan Williams <dan.j.williams@intel.com>
Subject: mm: teach pfn_to_online_page() to consider subsection validity

pfn_section_valid() determines pfn validity on subsection granularity
where pfn_valid() may be limited to coarse section granularity. 
Explicitly validate subsections after pfn_valid() succeeds.

Link: https://lkml.kernel.org/r/161058500148.1840162.4365921007820501696.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: b13bc35193d9 ("mm/hotplug: invalid PFNs from pfn_to_online_page()")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: David Hildenbrand <david@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Qian Cai <cai@lca.pw>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory_hotplug.c |   23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

--- a/mm/memory_hotplug.c~mm-teach-pfn_to_online_page-to-consider-subsection-validity
+++ a/mm/memory_hotplug.c
@@ -308,11 +308,26 @@ static int check_hotplug_memory_addressa
 struct page *pfn_to_online_page(unsigned long pfn)
 {
 	unsigned long nr = pfn_to_section_nr(pfn);
+	struct mem_section *ms;
 
-	if (nr < NR_MEM_SECTIONS && online_section_nr(nr) &&
-	    pfn_valid_within(pfn))
-		return pfn_to_page(pfn);
-	return NULL;
+	if (nr >= NR_MEM_SECTIONS)
+		return NULL;
+
+	ms = __nr_to_section(nr);
+	if (!online_section(ms))
+		return NULL;
+
+	/*
+	 * Save some code text when online_section() +
+	 * pfn_section_valid() are sufficient.
+	 */
+	if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) && !pfn_valid(pfn))
+		return NULL;
+
+	if (!pfn_section_valid(ms, pfn))
+		return NULL;
+
+	return pfn_to_page(pfn);
 }
 EXPORT_SYMBOL_GPL(pfn_to_online_page);
 
_

Patches currently in -mm which might be from dan.j.williams@intel.com are

mm-fix-page-reference-leak-in-soft_offline_page.patch
mm-move-pfn_to_online_page-out-of-line.patch
mm-teach-pfn_to_online_page-to-consider-subsection-validity.patch
mm-teach-pfn_to_online_page-about-zone_device-section-collisions.patch
mm-fix-memory_failure-handling-of-dax-namespace-metadata.patch