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Date: Mon, 25 Apr 2022 10:31:14 -0400
From: Zi Yan <zi.yan@...t.com>
To: David Hildenbrand <david@...hat.com>, linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
Vlastimil Babka <vbabka@...e.cz>,
Mel Gorman <mgorman@...hsingularity.net>,
Eric Ren <renzhengeek@...il.com>,
Mike Rapoport <rppt@...nel.org>,
Oscar Salvador <osalvador@...e.de>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Andrew Morton <akpm@...ux-foundation.org>,
Zi Yan <ziy@...dia.com>
Subject: [PATCH v11 2/6] mm: page_isolation: check specified range for unmovable pages
From: Zi Yan <ziy@...dia.com>
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.
Signed-off-by: Zi Yan <ziy@...dia.com>
---
mm/page_isolation.c | 47 ++++++++++++++++++++++++++++++++-------------
1 file changed, 34 insertions(+), 13 deletions(-)
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index df49f86a6ed1..c2f7a8bb634d 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -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,
- int migratetype, int flags)
+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;
}
--
2.35.1
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