From 9f605f260594f99b950062fd62244251e85dbd2b Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 25 Feb 2021 17:16:57 -0800 Subject: 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 Reported-by: Michal Hocko Acked-by: Michal Hocko Reviewed-by: David Hildenbrand Reviewed-by: Oscar Salvador Cc: Naoya Horiguchi Cc: Qian Cai Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'mm/memory_hotplug.c') diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index abe43c1ae920..fc6cdd99941b 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 -- cgit