From 9f605f260594f99b950062fd62244251e85dbd2b Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Thu, 25 Feb 2021 17:16:57 -0800
Subject: [PATCH] mm: move pfn_to_online_page() out of line
Patch series "mm: Fix pfn_to_online_page() with respect to ZONE_DEVICE", v4.
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/ 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.
This patch (of 4);
pfn_to_online_page() is already too large to be a macro or an inline
function. In anticipation of further logic changes / growth, move it out
of line.
No functional change, just code movement.
Link: https://lkml.kernel.org/r/161058499000.1840162.702316708443239771.stgit@dwillia2-desk3.amr.corp.intel.com
Link: https://lkml.kernel.org/r/161058499608.1840162.10165648147615238793.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/memory_hotplug.h | 17 +----------------
mm/memory_hotplug.c | 16 ++++++++++++++++
2 files changed, 17 insertions(+), 16 deletions(-)
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 15acce5ab1064..3d99de0db2ddb 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -16,22 +16,7 @@ struct resource;
struct vmem_altmap;
#ifdef CONFIG_MEMORY_HOTPLUG
-/*
- * Return page for the valid pfn only if the page is online. All pfn
- * walkers which rely on the fully initialized page->flags and others
- * should use this rather than pfn_valid && pfn_to_page
- */
-#define pfn_to_online_page(pfn) \
-({ \
- struct page *___page = NULL; \
- unsigned long ___pfn = pfn; \
- unsigned long ___nr = pfn_to_section_nr(___pfn); \
- \
- if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr) && \
- pfn_valid_within(___pfn)) \
- ___page = pfn_to_page(___pfn); \
- ___page; \
-})
+struct page *pfn_to_online_page(unsigned long pfn);
/*
* Types for free bootmem stored in page->lru.next. These have to be in
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index abe43c1ae9204..fc6cdd99941bb 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -300,6 +300,22 @@ static int check_hotplug_memory_addressable(unsigned long pfn,
return 0;
}
+/*
+ * Return page for the valid pfn only if the page is online. All pfn
+ * walkers which rely on the fully initialized page->flags and others
+ * should use this rather than pfn_valid && pfn_to_page
+ */
+struct page *pfn_to_online_page(unsigned long pfn)
+{
+ unsigned long nr = pfn_to_section_nr(pfn);
+
+ if (nr < NR_MEM_SECTIONS && online_section_nr(nr) &&
+ pfn_valid_within(pfn))
+ return pfn_to_page(pfn);
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(pfn_to_online_page);
+
/*
* Reasonably generic function for adding memory. It is
* expected that archs that support memory hotplug will
--
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