Commit 844fbae6 authored by Zi Yan's avatar Zi Yan Committed by Andrew Morton
Browse files

mm: page_isolation: check specified range for unmovable pages 

Enable set_migratetype_isolate() to check specified range for unmovable
pages during isolation to prepare arbitrary range page isolation.  The
functionality will take effect in upcoming commits by adjusting the
callers of start_isolate_page_range(), which uses
set_migratetype_isolate().

For example, alloc_contig_range(), which calls start_isolate_page_range(),
accepts unaligned ranges, but because page isolation is currently done at
MAX_ORDER_NR_PAEGS granularity, pages that are out of the specified range
but withint MAX_ORDER_NR_PAEGS alignment might be attempted for isolation
and the failure of isolating these unrelated pages fails the whole
operation undesirably.

Link: https://lkml.kernel.org/r/20220425143118.2850746-3-zi.yan@sent.com


Signed-off-by: default avatarZi Yan <ziy@nvidia.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Eric Ren <renzhengeek@gmail.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b48d8a8e

mm/page_isolation.c

+34 −13
Original line number Diff line number Diff line
@@ -16,7 +16,9 @@ 
#include <trace/events/page_isolation.h>



/*

 * This function checks whether pageblock includes unmovable pages or not.

 * This function checks whether the range [start_pfn, end_pfn) includes

 * unmovable pages or not. The range must fall into a single pageblock and

 * consequently belong to a single zone.

 *

 * PageLRU check without isolation or lru_lock could race so that

 * MIGRATE_MOVABLE block might include unmovable pages. And __PageMovable
@@ -28,12 +30,15 @@ 
 * cannot get removed (e.g., via memory unplug) concurrently.

 *

 */

static struct page *has_unmovable_pages(struct zone *zone, struct page *page,

static struct page *has_unmovable_pages(unsigned long start_pfn, unsigned long end_pfn,

				int migratetype, int flags)

{

	unsigned long iter = 0;

	unsigned long pfn = page_to_pfn(page);

	unsigned long offset = pfn % pageblock_nr_pages;

	struct page *page = pfn_to_page(start_pfn);

	struct zone *zone = page_zone(page);

	unsigned long pfn;



	VM_BUG_ON(ALIGN_DOWN(start_pfn, pageblock_nr_pages) !=

		  ALIGN_DOWN(end_pfn - 1, pageblock_nr_pages));



	if (is_migrate_cma_page(page)) {

		/*
@@ -47,8 +52,8 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page, 
		return page;

	}



	for (; iter < pageblock_nr_pages - offset; iter++) {

		page = pfn_to_page(pfn + iter);

	for (pfn = start_pfn; pfn < end_pfn; pfn++) {

		page = pfn_to_page(pfn);



		/*

		 * Both, bootmem allocations and memory holes are marked
@@ -85,7 +90,7 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page, 
			}



			skip_pages = compound_nr(head) - (page - head);

			iter += skip_pages - 1;

			pfn += skip_pages - 1;

			continue;

		}
@@ -97,7 +102,7 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page, 
		 */

		if (!page_ref_count(page)) {

			if (PageBuddy(page))

				iter += (1 << buddy_order(page)) - 1;

				pfn += (1 << buddy_order(page)) - 1;

			continue;

		}
@@ -134,11 +139,18 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page, 
	return NULL;

}



static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)

/*

 * This function set pageblock migratetype to isolate if no unmovable page is

 * present in [start_pfn, end_pfn). The pageblock must intersect with

 * [start_pfn, end_pfn).

 */

static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags,

			unsigned long start_pfn, unsigned long end_pfn)

{

	struct zone *zone = page_zone(page);

	struct page *unmovable;

	unsigned long flags;

	unsigned long check_unmovable_start, check_unmovable_end;



	spin_lock_irqsave(&zone->lock, flags);
@@ -155,8 +167,16 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ 
	/*

	 * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.

	 * We just check MOVABLE pages.

	 *

	 * Pass the intersection of [start_pfn, end_pfn) and the page's pageblock

	 * to avoid redundant checks.

	 */

	unmovable = has_unmovable_pages(zone, page, migratetype, isol_flags);

	check_unmovable_start = max(page_to_pfn(page), start_pfn);

	check_unmovable_end = min(ALIGN(page_to_pfn(page) + 1, pageblock_nr_pages),

				  end_pfn);



	unmovable = has_unmovable_pages(check_unmovable_start, check_unmovable_end,

			migratetype, isol_flags);

	if (!unmovable) {

		unsigned long nr_pages;

		int mt = get_pageblock_migratetype(page);
@@ -313,7 +333,8 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, 
	     pfn < end_pfn;

	     pfn += pageblock_nr_pages) {

		page = __first_valid_page(pfn, pageblock_nr_pages);

		if (page && set_migratetype_isolate(page, migratetype, flags)) {

		if (page && set_migratetype_isolate(page, migratetype, flags,

					start_pfn, end_pfn)) {

			undo_isolate_page_range(start_pfn, pfn, migratetype);

			return -EBUSY;

		}