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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>
This commit is contained in:
Dan Williams 2021-02-25 17:16:57 -08:00 committed by Linus Torvalds
parent fbcc8183a4
commit 9f605f2605
2 changed files with 17 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
include/linux/memory_hotplug.h
View File

@ -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

16
mm/memory_hotplug.c
View File

@ -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