Re: [PATCH v3] mm: Check if section present during memory block registering

From: Andrew Morton
Date: Wed Aug 26 2015 - 17:51:37 EST


On Wed, 26 Aug 2015 14:38:35 -0700 (PDT) David Rientjes <rientjes@xxxxxxxxxx> wrote:

> > --- linux-2.6.orig/drivers/base/node.c
> > +++ linux-2.6/drivers/base/node.c
> > @@ -390,7 +390,18 @@ int register_mem_sect_under_node(struct
> > sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
> > sect_end_pfn += PAGES_PER_SECTION - 1;
> > for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
> > - int page_nid;
> > + int page_nid, scn_nr;
> > +
> > + /*
> > + * memory block could have several absent sections from start.
> > + * skip pfn range from absent section
> > + */
> > + scn_nr = pfn_to_section_nr(pfn);
> > + if (!present_section_nr(scn_nr)) {
> > + pfn = round_down(pfn + PAGES_PER_SECTION,
> > + PAGES_PER_SECTION) - 1;
> > + continue;
> > + }
> >
> > page_nid = get_nid_for_pfn(pfn);
> > if (page_nid < 0)
>
> scn_nr should really be unsigned long, but it would probably be better to
> simply use if (!pfn_present(pfn)) rather than store the section number.

Yup. I was feeling lazy but you motivated me.

<grunt, wheeze>

--- a/drivers/base/node.c~mm-check-if-section-present-during-memory-block-registering-fix
+++ a/drivers/base/node.c
@@ -390,14 +390,13 @@ int register_mem_sect_under_node(struct
sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
sect_end_pfn += PAGES_PER_SECTION - 1;
for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
- int page_nid, scn_nr;
+ int page_nid;

/*
* memory block could have several absent sections from start.
* skip pfn range from absent section
*/
- scn_nr = pfn_to_section_nr(pfn);
- if (!present_section_nr(scn_nr)) {
+ if (!present_section_nr(pfn_to_section_nr(pfn))) {
pfn = round_down(pfn + PAGES_PER_SECTION,
PAGES_PER_SECTION) - 1;
continue;
_

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